Epoxy Sand Cores for DIY Foundry

How to make hollow castings by utilising epoxy resin as a binder for sand cores. The resin is relatively cheap and readily available and you don't need to keep a cylinder of CO2 gas on hand to harden sodium silicate and sand which is the traditional method for making cores.

[@joejava]

I seen a guy use epoxy sand to mold many parts to make a complete fully functional 1911 firearm using this method as well as moldable wax mixed together with sand many years ago as a teenager and the guy lived down the street from me I had learned a hell of a lot from that man. Anyway great video and I did enjoy it and this video reminded me of that guy down the street from me at a kid.

[@karlsinger4760]

I had the same idea and looked it up to see if it works. You appear to be the only one to have made a video on KZbin about epoxy cores. Now I know how well it actually works. Thank you!

[@pgs8597]

G’day Mark, I’ll have to keep the epoxy recipe in mind when I do a core, very impressed. Nice casting also. Cheers Peter

[@richards6452]

Mark, great idea using epoxy as the binder. It was easy to remove the core probably as a result of the following. The epoxy, being an organic long chain polymer, became pyrolised as the molten metal came in contact with the epoxy in the relative absence of oxygen. This leaves the sand with a carbon matrix still supporting the structure but it has lost its strength and becomes friable once again. The black is the carbon within the sand particles. Keep going, love your channel, Richard

[@Preso58]

Richard, thanks for that. I am no chemist but I was thinking that the heat was creating a physical change in the matrix. Curiously though, I fully expected to smell the epoxy burning out or to see a lot of smoke but there is almost no evidence of anything unusual during the pour. Must use that word in casual conversation "pyrolised" Love it!

[@markfryer9880]

@@Preso58 Don't forget to include the term carbon matrix and organic long chain polymer.

[@markfryer9880]

Richard if epoxy is an organic long chain polymer why does it stink so much when you mix it up?

[@walterashley149]

@@markfryer9880 because of whom epoxy is as a person.

[@dginia]

Very interesting. A couple of ideas. When printing the core box, leave a little gap at each corner to make pry bar insertion easier. Also, carnauba car wax might be good inside the core box.

[@Preso58]

Dennis, I have refined the method I use for these core boxes. I now print in flexures or fine gaps so that it is possible to flex the corebox halves away from complicated cores. I also print in bevels to pry the halves apart easily. I have moved on to using a beeswax and carnauba wax mix for mould release. So - great minds think alike. I have another video here that shows the new method. It starts at about 03:45 kzbin.info/www/bejne/oJ-6goOphNyVlZY Regards, Mark

[@Zortorond]

Thank you! I was looking for the alternative to the sodium silicate and I find your experience rather interesting;)

[@pf465]

Wonderfully done, I'm so impressed, thank you for documenting this. I understand the need to do this as it's cost prohibitive to order online, but the experience is priceless.

[@Preso58]

Thank you! Regards, Mark

[@AdeSwash]

Hello Mark, thankyou for your video, I have just started out in casting aluminum, just small engine cylinders for model engines, and didnt want to invest in CO2 for now, so I tried your method with the resin and it worked brilliantly - thank you!

[@Preso58]

Thanks. It works for me. I did buy some sodium silicate and the vendor sent it in plastic milk bottles. They split after about 12 months and the liquid spilled right through my paint storage locker. It made a huge mess and with that and having to find CO2 gas it didn't seem worth it for the few cores that I made. At least the epoxy is easy to store and it doesn't go off so for me it's worth having to wait for it to cure. Regards. Mark

[@markfryer9880]

Good video Mark. You earned yourself another Aussie subscriber.

[@lv_woodturner3899]

Well done. Glad that the casting worked first time. I am eager to see the machining video. Dave.

[@Preso58]

Dave, Well, that one worked but I did another yesterday where the core was perfect and I messed up the casting 😥 Still so much to learn!

[@tomayrscotland6890]

Hi Mark! Tom Copland here watching your channel, My Father was a Brass Moulder as was my Grandfather' With Bull's Manganese & Marine in Yoker Glasgow. I myself have been starting up a couple of project's in Aluminum got my foundry built but seems i am lacking core moulding skills so I will watch your channel and ( Myford boy's channel ) and just keep practicing till I get it right, I have plenty of CO2 as I do a lot of welding. So back to the learning curve. Thanks's for all your info.

[@Preso58]

Tom, metal casting is a particularly deep rabbit hole but it's so satisfying when you get an awkward casting to work. I generally count on having to do any casting twice so it's a bonus when it works out first time around. I have been watching Clarke Easterling at the Windy Hill Foundry channel for some years now. He is a very experienced foundryman who mainly casts in iron however even he has failures now and then. Another good source of information is Olfoundryman's channel. He has had to give up foundry work due to illness but he has a wealth of videos on his channel. Mostly he works in aluminium and he is a professional foundryman with very extensive knowledge of metallurgy. I must say that having a 3D printer is the amateur foundryman's best friend. Making patterns and core boxes is so much easier using that technology. BTW, we visited Glasgow a few years ago. We particularly enjoyed the Kelvingrove Art Gallery and Museum. Regards, Mark

[@ianbertenshaw4350]

Fantastic video Mark !

[@CraigLYoung]

I like that technique! Going to have to try it.

[@davidbrown9914]

This was so informative. i'm grateful for your time to teach this. thank you.

[@Preso58]

David, sodium silicate is still probably the better option if you can get a reliable supply and if you can get your hands on CO2 gas but for me it's not really an option. The epoxy works well and the cores are very strong but the downside is having to wait for it to cure. Regards, Mark

[@richardmckay3844]

Excellent video Mark. Thanks for sharing. Always enjoy your channel. Continue with your successes and fails.Best regards from Scotland

[@Preso58]

Richard from Scotland, we will be visiting your fine part of the world in late August. We are doing an epic road trip from London, through Wales and on up to Scotland but due to time constraints we won't be able to get right up to Inverness but we are going to Fort William. We are especially looking forward to Glasgow and Edinburgh. Cannot wait! Regards, Mark Presling

[@richardmckay3844]

@@Preso58 Hello Mark, Looks like a very busy schedule for your holiday visit. No doubt you will make adjustments as required to ensure your visit will be all you are hoping to do. Very best wishes for a memorable and enjoyable visit. Richard

[@ScottHiland]

Neat process, always a pleasure to watch you working in the shop. Also, +1 for using fancy terms like friable. :D

[@Preso58]

Oooh! I just learned a new word from a previous commenter - "pyrolised" which is used to describe what happens when a polymer burns in a low oxygen environment. Can't wait to use that one in casual conversation! Thanks for watching.

[@thomasheisler]

Mark, great job, I would call that flawless....now I personally would try as a second experiment, doing 4 at one time while doing lost wax casting with a latus. no real reason but to experimenting. But as someone that has never done it, I am very impressed. Thank you

[@JourneymanRandy]

Nice looking casting. You are getting good at this.

[@Preso58]

Not good enough unfortunately. I made a great core yesterday but stuffed up the casting. You'll get to see it soon. Have your hanky ready. It certainly made me cry!

[@chisdalton9652]

good to hear about the failures I followed a similar pattern, but sweet when it finally works... Thanks for the vid

[@yvesdesrosiers2396]

G'day Mr P. Looking forward to that metering valve video. I have made some investments in sheet metal tools and am planning to build a good size media blaster. So that valve is an excellent idea. Thanks for sharing.

[@Preso58]

Yves, The metering valve video is up. I have been using it and it is an improvement on the stock pickup tube that is supplied with the blasting cabinet but still not perfect. I am now making a replacement blast gun which I am hoping will be a complete solution.

[@karm65]

Try using a plastic bag ziplock bag to keep the CO2 concentrations higher for longer for a complete set

[@Preso58]

Now that I think about it, I did use that method for a really large core that I did several years ago. It didn't set straight away so I left it sealed in the bag overnight and then it came out OK. I can see though that the epoxy method is going to be cheaper for me since there is only the one consumable material that you need to buy. The amount is quite small too.

[@B60IN3]

Worked really great. Subscribed. Thanks for tip.

[@jchidley]

Helpful and clear explanations. Thanks!

[@woodscreekworkshop9939]

Very interesting technique, enjoyed it!

[@theonlybuzz1969]

Cheers prezzo for another great video, thanks from the other side of the world 👍

[@crazyfeller5704]

Great content as always. Thanks again for sharing.

[@garagemonkeysan]

Nice video. Very instructional. Congrats it came out on the first attempt! Cheers. : )

[@kevinhgreaves]

Give yourself a big pat on the back. I also tried the Sodium Silicate and failed. Your video has given me fresh inspiration. Well done 🤝

[@Preso58]

Thanks, the epoxy works for me, every time! I must give credit to Luckygen1001 who inspired me to have a go at it. Regards, Mark

[@DudleyToolwright]

Wonderfully educational video, failures and all. Cheers.

[@Preso58]

Dudley, I have gotten better at this casting sorcery over the years. It is definitely one of the "black arts". Regards, Mark

[@LelandRJohnson]

Another GREAT video.

[@rionmotley2514]

Thanks for a great walk-through. I've been having half-baked NaSiO2 core results, and had thought of using epoxy, I think I'll take this as a definitive yes, and I'll be sanding my core box! *high five*

[@solomonariel2834]

I know Im kinda off topic but do anyone know of a good site to stream new tv shows online?

[@langstonzachariah546]

@Solomon Ariel I dunno I use flixportal. just google after it :D -langston

[@solomonariel2834]

@Langston Zachariah Thank you, signed up and it seems like they got a lot of movies there :D I appreciate it!

[@langstonzachariah546]

@Solomon Ariel You are welcome :D

[@tobhomott]

Cool! I've heard of epoxy bonded cores, but never been sure if maybe you need some special type of epoxy. Looking forward to the rest.

[@Preso58]

Tobho, I think any sort of epoxy would work. I have some 5:1 ratio West System boatbuilding epoxy that I am keen to try. I did a second core yesterday with the 2:1 mix and it came out quite well. The main struggle is to get it out of the 3D printed corebox. I am thinking that a wooden corebox would be best but I will have to use that as a selling point with my wife when I float the idea of buying a CNC router! 😁

[@opendstudio7141]

That's quiet exciting. I could feel your exuberance 15,000 kilometers away and on a time delay. :)

[@Preso58]

Thanks, No one was more surprised than I was when that core turned out the way it did!

[@bclare2544]

Another good video Mark,would you consider at some stage making a video showing your 3d printer setup and how you go about designing and printing your patterns,Cheers from Tasmania,Bill.

[@Preso58]

Bill, I did a series of videos quite early on when I started this KZbin thing on building a spot welder. I think it was the very first episode on the spotwelder play list. It shows how I model the finished part and then how I add on the machining allowance and the draft angles. I use Autodesk Inventor but most 3D CAD packages should be able to do the same. At the time I did the spot welder I had an open source, home build 3D printer but I recently upgraded to a Creality Ender 3. It seems to be much more reliable and much quieter and I also ditched Repetier Host and started using Cura for the post processing. Despite being frustrated at first with Cura I can now see why it is the go to solution for many makers. I just checked and the video is here kzbin.info/www/bejne/haOWo4ewgdaBbqM Regards, Mark

[@thisnicklldo]

Very nice. You have a process that works, so it's all theoretical, but regarding the CO2 system: other commenters have wondered if your home made sodium silicate was pure enough. Also, I heard you mention that you used beach sand - if you got this from your local beach, which I believe is in tropical Queensland, then likely there's quite a carbonate content to the sand. Most beach sand is pure silica, but not the stuff that comes from e.g. reefs, and you have quite a big one nearby. The carbonate may combine with the sodium silicate to produce enough non-porous carbonates to prevent diffusion. Really, it's remarkable that CO2 can diffuse so readily through the fairly solid paste that forms the uncured core, so clearly it's pretty special stuff.

[@Preso58]

I am thinking that my DIY sodium silicate is the culprit. I was able to buy some commercially made stuff several years ago. The vendor shipped it to me in two, two litre plastic milk bottles. One split in transit and contaminated the box of mail at the post office. The other split spontaneously several months later and ran down all the shelves in my paint locker. It was a nightmare to clean up and there are still traces of it on the bottom of some paint cans. However it worked quite well and I did use ordinary beach sand. However, I did a second epoxy sand core yesterday and it worked perfectly. I had to reinforce it with some stainless steel tig wire but it was a fairly challenging shape. The core did it's job and came out fairly easily but not as easily as the first one due to it's shape and how it was surrounded by the cast metal. The truly sad thing is that I was impatient (a curse) and poured the metal before it was hot enough. It filled 98% of the sand cavity but the 2% that was missing was in a critical area. Still, it's all a learning experience! Regards, Preso

[@bill200262]

Very good

[@garyskowbo3564]

Hi Mark great looking casting, i was wondering what sand you use for your molds and where you get it. Great video, thanks for sharing your knowledge. Keep them coming if you can,regards from the USA 👍

[@Preso58]

Gary, I made up a new batch of greensand recently. I purchased 1/4 cubic metre of "Ballina White Sand" (Northern New South Wales) from my local landscape supplier. It is almost a pure silica sand and it has been washed by the supplier. It has a much finer grit size than the local beach sand from where I live (near Noosa in South East Queensland) It has no natural clay content so I added about 10% to 15% bentonite clay which I purchased from my local rural supply company. It is used as a additive for sealing dams. The sand takes a lot more ramming than I would like but as far as I am aware, there are no naturally occurring deposits of clay bearing sands where I live. I am very envious of other amateur foundrymen who can just dig up a trailer load of sand from the side of the road and use it with minimal preparation. If you watch olfoundryman you will see that he uses a naturally occurring sand from the suburbs around Melbourne. It seems to ram very easily and is very firm with good finish texture. Regards, Mark Presling

[@TomMakeHere]

Is this from the recent Hare and Forbes sale? Not going to lie I also bought tools that will add 'significant advantages and gains to the workshop' :)

[@EmmaRitson]

about 6-7% seems to make good hard cores. also you want DRY sand. Ive never had luck with anything but store bought sodium silicate too.

[@EmmaRitson]

the epoxy is probably fine in iron with some zirconia paint on top. wonder if anyone did that

[@Preso58]

I must say that I am a bit lax at measuring stuff out. I really should try to be more scientific about it. I did another core yesterday which was slightly more dense, probably about 3-4% and the core prints didn't burn off like they did on the first one. I also reinforced the long slender arms with TIG welding wire. It was a little harder to dig out of the casting but you'll get to see the results soon. Spoiler alert..... the casting was a fail. Core good, casting bad!

[@thomasutley]

Beautiful!

[@Preso58]

Thanks Tom, however you have seen my Instagram post of the latest failure so it's definitely a swings and roundabout thing! Regards, Mark

[@davidfe47]

Perfect use of on hand materials with the epoxy. You forgot the marshmellows with the excess heat of the melting flame. Ummm-- no initials & date on your work! i.e. MP MMXIX Looking to see Raff in forth coming episodes.

[@Preso58]

I must say that I don't particularly like toasted marshmallows but I had considered that particular sight gag in the episode about the furnace build. I am thinking that I should be leaving the comedy to "This Old Tony " He does it so well!

[@davidfe47]

Just do the HUMOR in ypur own style. Love your videos

[@richardmckay3844]

Thanks Mark for your reply, I would be delighted and it would be a real pleasure to meet you if you can spare a little of your time ?. I live 8 miles from Glasgow in retirement. Either way , have a wonderful trip . Kind Regards from Bonnie Scotland 😊 Richard

[@gulf4yankee]

I am experiencing the exact same problem. I have a very intricate detailed 3D core box. The sand and sodium silicate is hard to fully pack into the cavity and completely fill all the nooks and crannies, after hardening with CO2, the core does not want to release without breaking or crumbling away. I am going to try the release agent and epoxy with sand.

[@Preso58]

For what it's worth, I have not had one failure with the epoxy sand mix but the down side is that you have to wait for at least 12 hours for the epoxy to set, at least the epoxy that I use anyway. There are probably quicker setting formulas out there though. I did a video recently on making core boxes that have built in flexures so it is easier to get the cores out. kzbin.info/www/bejne/oJ-6goOphNyVlZY check it at about the 3 minute mark. Regards, Mark

[@paulmuff9883]

Hi , the first attempt with Silicon with me was that they would not harden but so worked out that I was adding too much silicon to the sand and I think that’s what you did when I measured it out correctly they were rocksolid every time nice video

[@Preso58]

Paul, I have made successful cores with sodium silicate before but this was when I had access to CO2 gas cylinders at work for gassing the sand mix. Now that I have to do all this work at home it is more economical to use the epoxy sand method. Certainly, the sodium silicate mix is quicker and it is very robust but if you're not in a hurry the epoxy works too. Regards, Mark

[@jamest.5001]

I was thinking maybe thin some wood glue with alcohol. Then mix with sand, the alcohol should evaporate fairly quick. And leave a thin film of glue to hold the sand together, and should turn back to sand after the heat of the pour. This was basically as good as I think you can expect though! Came out much easier than I thought!!

[@Preso58]

I read a recipe for making cores which incorporated wallpaper paste, flour and maybe sawdust mixed in with the sand. Evidently it worked but it had to be baked in an oven to make it set and by all accounts it smelled pretty bad. I think that anything that will bind with the sand to make a relatively strong matrix would work. Regards, Mark

[@samxerrie4140]

hey mark with the sodium silicate cores instead of co2 try using a blow torch the flame will harden the cores

[@AlbiesProductsOnline]

I have found if I mix in to the sodium silicate and sand mix a couple of tablespoons of plaster of Paris the chemical reaction between them activates quickly and sets very hard without co2. Here in Australia if you go to Bunnings you can buy small bottles of welding gasses including co2 for under $50 and it’s a swap and go system so you own the bottle and it only costs a fraction of that to swap around $20-$30 at the most depending of the gas and they do have the same deal now right up to the largest bottles

[@Preso58]

I have checked out the swap and go Bunnings cylinders but I am starting to think that the epoxy cores are going to be my preferred method. I did a second one yesterday and it worked perfectly. I messed up the casting, but the core was fine! 😢 You'll get to see that particularly sad story soon.

[@jaredwilliams5252]

That using the bike co2 probably would have worked but most molds used for making multiple cores like what luckygn and myford boy use are usually pretty smooth and has some form of release agent in it.

[@Preso58]

Jared, I started using a beeswax and carnuaba wax blend as a release agent and it works great. Sanding the core boxes definitely helps too.

[@skyfreakwi]

Hey mark, I'm sure it's been mentioned or asked but have you ever considered the lost foam method? It just seems so insanely easy! You could even do a lost pla mold. Just put a little sand in a bucket, add foam plug or pla coated in drywall refractory, add a sprue and a feeder fill with sand and vibrate. Melt metal of your choice and dump it in your sprue. A little smoke a little flame, and you have as perfect-ish casting!

[@Preso58]

I have seen that method used but so far I haven't tried it. I have seen some quite complex castings made that would otherwise by very difficult to create and it means that you don't need to worry about draft angles or cores. One day I will give it a go. Regards, Mark

[@skyfreakwi]

@@Preso58 sorry for my previous... I edited it for the 7 typos and did one rephrasing. And yeah, give it a go. I can't wait to get my furnace going to try! No cores, no draft angles, smooth surface finishes, unlimited complex shapes! And as always great job, good content, informative, your doing the good work here! Cheers!

[@coinsmith]

Throughout the 19th century and earlier, foundries used molasses as a binding agent for the sand to make cores. Once dried the cores would be baked and become quite firm. After casting the cores would be easily flushed out with a stream of water. This is how hollow objects such as cannon shells etc were made.

[@Preso58]

Charles, I have read about that technique. I believe the smell produced by the baking cores was quite strong. Regards, Mark Presling

[@coinsmith]

Ah, but not unpleasant!

[@luckygen1001]

I have been using epoxy resin cores in my cast iron castings for over 20 years. I would never go back to using sodium silicate. On a side note if you put a sodium silicate core in a microwave oven it will go hard.

[@Preso58]

Well, credit to you then because I was watching your video on making a shielded impeller and that's what gave me the idea. I didn't know that sodium silicate would harden in a microwave but I did make a quite large sodium silicate core in a PVC mould and it didn't harden all the way through when I gassed it. I had access to argon/CO2 welding gas at the time so maybe the concentration of CO2 wasn't high enough. I put the whole thing in a low conventional oven and it seemed to do the trick. It's funny that epoxy sand cores aren't documented all that well on KZbin. I couldn't find a lot of reference to the technique on forums either. I enjoy watching your videos...... so much to learn about this particular "black art". Regards, Mark

[@luckygen1001]

If you ever need any help with any problem you know where to come to. I was the first to use it but for some reason very few home foundry men use it.

[@Preso58]

Hi, I would very much like to get your opinion on a problem I am having with regard to gating on a 140mm aluminium bandsaw wheel that I cast today. The metal didn't quite flow all the way through the cavity. It left a small void on one of the spokes. I would appreciate it if you could take a look at a photo but I can't find your email address. If you could drop me a line at [e-mail] we could discuss some different approaches. I have been watching your latest videos on the induction furnace. Great stuff and very interesting. Cheers, Mark Presling

[@drewrogge4798]

I wonder if the sodium silicate sand was packed too tight in the core box. This may have prevented the CO2 from being able to flow to all parts of the sand. Also it was pretty interesting that we could see the layer lines from the print on the inside of the hole..

[@iteerrex8166]

It wasn't very solid even at the surface. The CO2 wasn't the problem, maybe the home made sodium silicate had impurities. Like he said it goes boom solid in no time.

[@Preso58]

I think that my DIY sodium silicate was suspect. I had some commercially made product a few years ago that worked quite well. However the epoxy is working for me and it is relatively cheap. I did a second core yesterday that worked perfectly so the first one was not a fluke. I am also surprised at how faithfully the 3D print texture shows up in the finished casting. Even the patterns that I took the time to fill, sand and paint still leave a slight texture in the outside of the castings.

[@iteerrex8166]

Mr Presling, I wonder if there were impurities in the sodium silicate, there sure was no problem with the CO2. Like you indicated as soon as you apply the CO2 it goes boom solid in very little time.

[@Preso58]

Tameem, I do think that the sodium silicate was suspect. I had some commercially made product a few years ago. It worked perfectly with a CO2/Argon welding gas mix. However the epoxy is working for me now. I made another core yesterday that was a success. You'll get to see it soon.

[@johnwhauserman]

I have been told 11% of the weight of your sand works great.

[@mrgreenswelding2853]

You can use a needle and syringe to inject co2 or put more holes in the core. Silicone spray is use as a release agent as well.

[@Preso58]

I have some silicone spray which I will use next time I do a core. I just recently did another using the Lithium grease and it didn't come out as easily as I had hoped but I suspect it is to do with the layer lines in the 3D printed core box. At some point I want to build or buy a CNC router for making core boxes but I am running out of room in my shop. I have already built one annex on to it and there is no room for another. I purchased a 20" container a few years ago to house some of the tools that I don't use very much and my two children immediately filled it up with the overflow from the various share houses they have lived in. There is probably some rule about nature abhorring vacuums there!

[@markfryer9880]

@@Preso58 Tell the kids to come and get their crap out of YOUR Container before you either start charging them to rent the space or you sell or bin the items. If you bin items don't forget to charge them for labour hire and bin/skip fees.

[@mwhelan53]

Ok, 2 things. 1. You have a symmetrical core, it is much easier to make the cores in 2 halves then glue them together. This is not an airy fairy idea, dad was a pattern maker, that is how the majority of core boxes were done. 2. With the silica sand you must expose it thoroughly to the CO2. making the core in 2 halves will help with this as will 'venting' the uncured sand with thin wire.

[@Preso58]

I realise that I made a lot of errors in my sodium silicate core technique but I now make my cores exclusively from sand and epoxy. It just saves me from having to keep CO2 gas on hand. Gluing the cores together with epoxy would be easy but I haven't done it that way yet. Thanks for the tips though. Regards, Mark

[@mwhelan53]

@@Preso58 Mark I noticed with some amusement re the sand epoxy mix. Reason being thats actually how the core boxes were made. Dad would make a positive core pattern (1/2), this was then 'cast' in the core box using epoxy and sand. Hope that made sense. It was a long time ago but I learnt a lot about the process of pattern making on Saturday mornings.

[@mrgreenswelding2853]

Bunnings has the same stuff as in the packet for cheap for a couple kg.

[@rocifier]

Ok, but going by texture consistency or volume means nothing because we don't know how much lye you used when dissolving the silica beads?

[@Preso58]

There are recipes online if you want to try making your own sodium silicate. I can't recall the exact ratios and at the end of the day I gave up on using it anyway because of the hassle of having to keep a cylinder of CO2 gas on hand. Regards, Mark

[@wesaderty]

Hi Mark! I'm starting in this wonderful world of castings and I would like it to satisfy my desire to learn. these days, I was thinking about a substitute for sodium silicate, and I thought: why not use a polyester or epoxy resin??? but, in my language, I didn't get anything about it. by the way, sorry for any mistranslations or use of wrong terms as I am using a translator. continuing, I realized that you used epoxy resin and it seems to me that the result was very good. do you think epoxy resin is better than silicate? sorry, maybe I've already mentioned my question in the video, but as I'm also a beginner in the language, I couldn't keep up. if you are kind enough to answer me, I will use the translator for understanding. ahhh, your casting was of great quality. congratulations! a big hug from Brazil

[@Preso58]

I have used both sodium silicate and epoxy and both give good results. The epoxy works better for me because I don't need to keep CO2 gas on hand to harden the core. Epoxy is relatively cheap too. It just takes longer to set. Regards, Mark

[@sellamslimane2974]

@@Preso58 hello, I am new to the field what is the intensity of adding co2 for the core, and what kind of epoxy you use thank you.

[@CMAenergy]

Why do you use CO to harden your silicate? I also would say you didn't mix the silicate adequately. I used to if I recall correctly, heat mine an it would set up or just let it stand if I recall. Good idea to use epoxy, But for release agent I am not sure if talc would work,It would probably solidify to the sand, Or to use a good oil base should allow for release.

[@Preso58]

I have had success with sodium silicate before. I think the amount of CO2 I gassed the sand with was inadequate. I made a core with sodium silicate which was quite large and I could tell it was not fully hardened. I left in in the hot sun for a day and it came out fine. I just like the idea the the epoxy will definitely go off no matter what. It seems to be very robust and I can avoid the outlay of having to rent a cylinder of gas. Regards, Mark

[@CMAenergy]

@@Preso58 that's correct

[@OstrichWrestler]

FDM 3D prints, while quite solid, are generally porous enough to let water drip through so air would have no problem finding its way out. Perhaps the CO2 just wasn't penetrating well enough because of it. Maybe a coating of the inside of the mold or a plastic bag would have helped. The epoxy method seems to work well for low volume stuff. Make sure you dispose of it properly though. We have enough micro-plastics hanging about. great vid btw

[@Preso58]

The funny thing was that early on when I first started making cores I made quite large ones with no problems. I was using CO2 MIG shielding gas to cure the sodium silicate. However, I don't have access to that any more (since retiring). I think my main problem with that little cylinder was that I just ran out of gas. Regards, Mark

[@Eservicecamer]

Why didn't you create the pouring basin directly ontop of the hole, why by the side. Just curious. Thanks

[@Preso58]

The offset pouring basin is a way of ensuring that the sprue is kept full during the pour and that air is not sucked down into the metal stream entering the mould. It takes some practice and careful observation to ensure that you are getting the flow right but once you get the hang of it the finished castings seem to have less porosity and the low velocity of the pour keeps sand particles from being dislodged. I learned the technique from Martin West (Olfoundryman), Regards, Mark

[@Vladviking]

I believe a coarser rougher sand would let the C02 "filter thru". Casting sand packs too densely. Not had good luck myself. Even with store bought Sodium silicate. I have used wire inside to reinforce. I just made the cores well in advance had a lot of holes in the form so as to have several days of drying. I have had such good success gluing broken cores back together I think I will just use a watered down wood glue in the mix next time. Also lined the mold with aluminum foil and left that on in the pouring flask.

[@Preso58]

I had considered using PVA glue to bond the broken core but I was also keen to try the epoxy as a binder. I have used it a lot since that first experiment and it has always worked out for me. Regards, Mark

[@Vladviking]

@@Preso58If I get in a rush I will surely use epoxy. I guess a thirty minute curing time would be fine.

[@diamondperformancefab5931]

That mini cylinder you used was probably just high pressure ambient air and not co2. Unless your sodium silicate was bad.

[@Preso58]

No, it was CO2 but there was insufficient volume to fully penetrate the core. The outer skin had hardened but the inner area was still sticky and wet. The best solution would be to use low pressure but high volume CO2 and allow it to fully permeate the core. Regards, Mark

[@notJW13383]

I use 2% epoxy to sand ratio and add acetone to make it easy to mix into the sand. I use fine, washed sand from Lowe’s as it preserves the pattern detail. I use the epoxy sand for the cope and drag not just cores. Warming the epoxy sand greatly reduces hardening time. Patterns can be more easily removed before the epoxy sand has fully hardened, when it is like soft clay.

[@Preso58]

John, good advice. I think that core experiment was done fairly early on in my foray into epoxy sand cores. I did some more recently and made the core boxes split almost all the way through so it is possible to flex the core box away from the hardened core. Heating the sand makes sense and I do have an oven that can be accurately set to low temperatures. I made a cope for a very small pattern using the epoxy sand mix and it worked great. For me, at least it's a lot more cost effective than keeping CO2 on hand and storing sodium silicate. Regards, Mark

[@georgealexandris8043]

How much acetone do you use ?do you mix it in the resin or the hardener ? Thanks 🙏

[@notJW13383]

@@georgealexandris8043 Mix resin and hardener together first and add just enough acetone to get watery viscosity.

[@georgealexandris8043]

@@notJW13383 thanks 🙏

[@steveone]

Could you use PVA mixed with sand for the core ?

[@Preso58]

Steve, It might work for small cores. PVA can be a bit rubbery when cured. There are recipes with mixes including flour, wallpaper paste and starch but they have to be baked and they stink! I did a second epoxy core yesterday and it will come up on a future video. It worked but the first attempt failed because it stuck in the 3D printed corebox. The second one came out perfect but I now heat the second part of the corebox to 100C in an oven to soften it. You can then peel it off fairly easily. It ruins the corebox though!

[@coryknipe5471]

I might suggest sprinkle baby powder or corn starch on the mold before adding sand.

[@petermarsh4993]

Dear Mark, I was wondering if you use more Sodium Silicate liquid than you did and to put your casting inside a container and inject the CO2 into the container. That may work better. As you said, MYFORDBOY demonstrates the method successfully. Cheers.

[@Preso58]

I have made sodium silicate cores before and they worked great. I was using MIG welding gas to cure the sodium silicate but I don't have access to that any more. (I was doing it at work). You can also cure the sodium silicate with moderate heat like in a low oven. I just find that the epoxy method is predictable and the cores are very durable and strong when done that way. Regards, Mark

[@petermarsh4993]

@@Preso58 Thats what becoming an expert is all about. One famous inventor claimed that he did not singularly invent the light bulb but he worked out 30,000 ways NOT to make them run. On another question: I’m trying to source two pack epoxy paint like you show. Can you give me a brand or outlet chain where I can purchase some please? I’d like to give it a go. Thanks.

[@unclebobsbees4899]

Mark, never thought of using epoxy for a core. Looks great. Here in the US the silicate is also known as water glass. Paint stores should recognize the name. We can actually get the silicate as 'garage floor sealer and carton adhesive'. It costs $30US for a gallon. Bob

[@Preso58]

I once purchased 2 litres of commercially made SS from and Ebay seller but it was delivered in plastic milk jugs which split, one in transit and the other some time later in my paint locker. It made a huge mess and it was really strange stuff to clean up. It would either harden like a film or crystallise into a white crust. Truly weird stuff! I can see why they would use it as an adhesive. I believe that water glass was used to preserve eggs! However, I think I will be sticking to the epoxy sand mix (no pun intended). I made another one a few days ago and it worked a treat!

[@MatthewTinker-au-pont-blanc]

It looks like the grains of sand weren't completely covered when you mixed the Sodium Silicate. Regards, Matthew

[@Preso58]

Matthew, I have made sodium silicate bonded cores before and they worked quite well, however, I was able to buy some commercial grade material for the ones that were successful. I also had access to a large cylinder of CO2 welding gas. Now that I am retired I have to make do with what I have on hand. The epoxy method works better than I expected though. I did a second one yesterday, it will come up on a future video. It was a fairly challenging one to do with three long, thin arms coming out of a larger bulkier centre section. I was able to reinforce it with some TIG welding wire and despite some tugging and levering, it came out of the corebox intact. The only downside is it takes up to 8 hours for the epoxy to cure. For a commercial application, that would be too long. So, I got a perfect core and then screwed up the casting, but you'll get to see it later. 😢

[@en2oh]

I wonder if the problem with the original core, you might have needed more concentrated ‘water gas’.

[@Preso58]

I must say I have never had a lot of success with sodium silicate. Usually it was due to not having a sufficient flow of CO2 gas to cure the core but it could be that the sodium silicate that I had was old or contaminated. Regards, Mark

[@thomassutrina7469]

Epoxy in a thermoset plastic that doesn't remelt. It becomes very brittle and losses strength as you found out but it is still a solid which is what held the sand together during pouring. " NASA chose an ablative heat shield composed of a brazed steel honeycomb structure impregnated with phenolic epoxy resin." The brittleness caused the ends not in the metal to fracture away.

[@Preso58]

In a way it is a good thing that the epoxy loses all it's bonding strength. It holds together just long enough to form the void and then it crumbles away when the cast is solid. I read that NASA used wooden heat shields on some of it's earlier re entry vehicles. The wood, or wood composite would burn and char and the plasma helped to dissipate the heat.

[@thomassutrina7469]

@@Preso58 I believe the USSR used wood.

[@earn_byars9773]

How about silicon mold for easy removed

[@Preso58]

Yes, that will work. Most of the specialty mould release agents would work well. Regards, Mark

[@TheJohndeere466]

I am no expert but from watching other videos, one thing that could have made your casting better is if you would have poured a little faster. The sprue hole should stay full at all times once you start pouring or it will pull in air and place the air in your casting somewhere. It looked like your sprue was only about half full most of the time while pouring.

[@Preso58]

James, it turns out that the offset pouring basin should be deeper and have a flat bottom. I was being tutored by Olfoundryman and he gave me a sound telling off for making the basin bowl shaped. I now realise that you can pour a lot faster without any danger of the metal overflowing if the basin is shaped correctly. Regards, Mark

[@TightOnesOfCNC]

27:53 for strange face

[@saltlessshakedowns4999]

You forgot your sprew cup. That is, maybe, why you have a lot of sand granules in your casting. Too much turbulence. The sprew cup is a funnel shape with one side flat and a flat bottom. When I made a perfect one... after the cast I cut it off, cleaned it up and used it as a button on my molds. Also, you should cut your sprew after you pack all the sand in the cope. It will create a cleaner sprew hole. This means it should have a taper to the cutter. Nice job on that casting!!

[@Preso58]

I have since changed my method for making the basin and sprue. I learned the technique from Martin at Olfoundryman. He took issue with the way I was making my pouring basin and gave me some valuable guidance on how to cut the shape required. The lighting in this video does make it hard to see how I made the basin but it was shaped like a round bottomed cup which is of course incorrect. Now I use a flat bottomed basin and it works just great. Regards, Mark

[@saltlessshakedowns4999]

@@Preso58 Good info. Thanks for showing your process and results!

[@roosterqmoney]

You might be able to rig up a vacuum chamber and then push CO2 into the vacuum chamber

[@andyolson7582]

What if you just used wood glue instead of epoxy?

[@Preso58]

I am not sure but it's worth a try. Whatever you use is just a temporary binder. I have heard of mixtures of wallpaper paste, flour and sand being used for cores. I guess the real issue is making sure it's not really flammable or likely to outgas in contact with the hot metal and also how easy it is to remove the core from the casting. Regards, Mark

[@wyohman00]

Preso, thanks for not saying that you've "invested" in a new tool....

[@Preso58]

Ha, ha! I once had a car salesman tell me that I must be quite excited to be investing in a new car. I quickly reminded him that the minute I drove the car out the showroom door it would drop 20% of it's value. How is that an investment? Regards, Mark Presling

[@bethelgues3918]

Epoxy doesn't need air I don't think, so no vent hole needed.

[@OneTequilaTwoTequila]

27:53 - I see a face inside the casting on the junction.

[@EDesigns_FL]

The addition of a little steel wire to your core might have made it easier to work with. Like with concrete, there's almost no tensile strength without reinforcement.

[@Preso58]

Funnily enough, I did exactly that yesterday. I used some stainless steel TIG wire to reinforce a core with three long slender arms. The core came out great but I semi ruined the casting. You'll get to see the whole sorry saga soon. Have your box of tissues ready!

[@AJ........]

Just as a novice, I probably would've made a solid casting and drilled out the centers...I wouldn't have dared to cast the interior chambers

[@Preso58]

That would work just fine. I was keen to see if epoxy sand cores would actually work. Since then I have used them a lot and they are quite predictable and remarkably strong. Regards, Mark

[@ben9433]

soda stream bottle might be a good source of co2

[@Preso58]

You're correct. I didn't realise you could buy those things in supermarkets. They have a much larger capacity than the little cylinders I purchased. Regards, Mark

[@smudgepost]

1:6 to 1:8 sodium silicate to sand is common.

[@NOBOX7]

you could have thrown the mold in the fire to burn the plastic away 10:17

[@Preso58]

I suppose so but I have had very little experience with sodium silicate cores so I don't know how robust they are. I have modified the way I make the 3D printed core boxes by printing in flexures so they can be pulled away from the core more easily. That way they can be used multiple times without having to scrap them. Regards, Mark

[@richardhodds7812]

Why not use oilsand for the cores. . CO2 and sodium silicate Use a bigger rod to make holes for gas penetration and rap the core box as you do for removing a pattern from the mould. Core box should be smooth and waxed to help release. This old technology from the sixties.

[@Preso58]

Richard, my main problem is keeping the CO2 gas on hand for gassing the cores. I don't do a lot of cores and it's not really worthwhile having a dedicated cylinder just for that job. The resin keeps indefinitely (mostly) and apart from the longer curing time it works quite well. Regards, Mark

[@Steve_Just_Steve]

Man the new foundry is ripping Preso! Do you ever watch a channel called SV Seeker? Guy named Doug that's building a giant boat in his backyard, actually lives not far from me in OK. Anyway, he has done quite a bit of casting for his boat you may enjoy watching. I watched him figure out using that silica is what made me think not him. Thanks for the great vids. Cheers

[@Preso58]

Steve, I have seen the SV Seeker videos come up on my recommended list. I not really a boat guy but I have been watching the Samson Boat Co. series and a fair bit of the Acorn to Arabella saga. I will check out Doug's work though. I'm always astonished by what you can glean from watching unrelated content. There's always some little nugget that you can adapt or store away for a future challenge. Regards, Preso

[@markfryer9880]

I thought that they were building the boat in the front yard to make it easier to load on to the low loader?

[@guye7763]

Remember the CO2 is heavier than air. That of course makes it dangerous but also makes it very easy to fill a drum with gas.

[@sellamslimane2974]

hello, I am new to the field what is the intensity of adding co2 for the core, and what kind of epoxy you use thank you.

[@Maurice419]

Maybe need to smooth the surface of your core mold.

[@Preso58]

I have made simple cores inside split PVC pipe. The resulting cored hole in the casting looks like it has been die cast. But you are correct. If I had spent more time filling the mould layer lines it would have turned out way smoother. Regards, Mark

[@SharkyMoto]

things you dont learn from youtube videos about casting: -it takes a long time, making the mold, preparing stuff, it takes AGES! -molten metal is hot (who would have guessed) you know its hot, but expiriencing the heat radiation of a crucible full of molten metal is really surprising and it could be a bad surprise if you are unprepared for it -skimming the dross is NOT easy, imagine fishing out a piece of shell from a egg in a cup, its just like that, but the egg would freeze solid whenever the spoon leaves the cup -the mold takes really long to cool, you can pour the stuff and take a nap, come back an hour or so later, thats roughly the point, you can get it out kinda safely, its still very hot, too hot to touch in any case, and also THE SAND IS HOT!! that should be the disclaimer after all casting videos here, it looks so simple and relatively quick, but its all but that, its maybe one of the hardest crafts to master. well done anyways, the part looks great!

[@Preso58]

I am in complete agreement! I had a frustrating session yesterday casting a replacement blasting gun/handpiece. The core turned out great but the casting was a fail. It took so long to make that I have decided to have a friend weld up the missing section rather than make a new core, mould, melt the metal, pour, put away all the gear, sweep the floor and still possibly end up with a second rate casting. So sad! Regards, Preso

[@markfryer9880]

Good comment Sharky

[@MegaBCAD]

Bit of a late comment I got unsubscribe somehow but a another cheap easy way to get co2 is a soda stream refills thay can be refilled ate woollys or use dry ice and do it your self

[@Preso58]

I saw those CO2 soda stream cylinders but the epoxy sand process seems to be working quite well for me. I just had a comment from Luckygen 1001 who has been using epoxy and sand for more than 10 years and it was in fact one of his videos that gave me the idea to try it.

[@tonygagey]

Try putting the core in a plastic bag, suck out the air and refill with co2

[@Preso58]

I have done that but the cost of keeping a cylinder of CO2 gas on hand is not worth it for the few occasions that I need to make cores. I am not sure where you live but here in Australia you need to either rent the cylinder or pay an upfront fee to purchase a cylinder and then pay for a refill. Either way, it can add up to over $200 per year or an initial cost of $200 plus $100 for the refill. I know you can purchase single use cylinders for things like soda stream gadgets, but again, it's an upfront cost. I have epoxy on hand for other projects so I may as well use it so that it doesn't exceed it's shelf life anyway. I find the epoxy cores to be very robust and strong and yet they break up easily when they need to be removed. Regards, Mark

[@popo5413]

LOL

[@_Junkers]

Just throwing my completely ignorant opinion out here.. I think if you talc'd the mold and used less sodium silicate, the sand would of breathed easier and expanded less, allowing for easy removal.

[@Preso58]

I must say I have not really persisted with sodium silicate much. It's not so easy to get here and the cost of the CO2 gas is also an issue. I find that the epoxy is relatively cheap and it does work as long as you are prepared to wait overnight for it to cure. Regards, Mark

[@markkoons7488]

II'm ten minutes into this video and as I click out want to suggest in the future you post videos of what works rather than all the tiresome failures.

[@Preso58]

Mark, thanks for your suggestion. I understand that some people want to find a specific solution to a problem or a guaranteed technique without wanting to wade through a lot of preamble. I don't have any advertising or sponsorship on my channel and it was never intended to be an "expert" channel. I started off just demonstrating what I enjoy doing as a "warts and all" narrative. I get that it can be a bit long winded but surprisingly, many people have commented that they appreciate seeing the failures as it reminds them that we all make mistakes. I try to show what goes wrong in the hope that someone might learn what not to do and the degree to which a technique might work given slightly different circumstances. In future I will try to include a guide in the description so that it will be possible to fast forward to the bit where the successful solution is documented. It's a pity you didn't skip forward a bit. I did eventually show a technique which was cheap, easy and successful. I have since repeated it and it was also successful. Regards, Mark Presling

[@jirvin4505]

The long version is always the best. That’s what fast forward I’d for if you are in a hurry. The failures teach valuable lessons

[@peterwadham9788]

I haven't read all the comments. While it is a very interesting idea. I have worked with epoxy for a long time and seen its health effects and the safety precautions we take when handling it. I have also seen the health effects first hand on some of my work mates!! When epoxy is allowed to exotherm, It gives off a highly toxic gas containing among other chemicals amine. This chemical is a known carcinogen. When doing anything in finished products that could cause things to catch fire we take major precautions. The only places you can dispose of wind turbine blades which are mainly epoxy resin, carbon fibre, kevlar and fibreglass is a regulated landfill or a high tech high temperature combustion unit. I know that the amount of epoxy that you are using is small and that you are using it in a well ventilated area. I have serious reservations about this process. www.cdph.ca.gov/Programs/CCDPHP/DEODC/OHB/HESIS/CDPH%20Document%20Library/epoxy.pdf