Lost Foam Casting: Making Plaster Feeders & Vents - by VOGMAN

[@markeastridge9649]

Greatly appreciate how you share your thinking process and relate to theory.

[@swdweeb]

Nice job Geoff. I always like seeing people making things that they use to make other things.

[@vogman]

Thanks. I just need to make another thing first ; )

[@swdweeb]

Isn't that always the case ;-)

[@hesperhurt]

Great video and loving your channel! Great content, easy listening/watching and not a drop of "YTber arrogance". Spot on mate and I'll be building a few waste oil burners for forges at our Makerspace in Wet Wales. Coming from an arts mould making background... I was in the middle of a massive weekend mould session. 28 piece high temp plaster of Paris mould for a ceramic chair. About halfway through I ran out of animal size (release agent). An old technician suggested using lard. Quick nip to the local Tesco later and it worked like a charm! Has the bonus of smelling like a full English when heated 😅👍

[@WaltSorensen]

The big risk in not baking to 400C as Martin (olfoundryman) says, or not baking long enough, is the water in the plaster can flash boil to steam and cause an explosion sending liquid metal everywhere. If your lucky the minimal bad thing that can happen is the plaster just cracks and liquid metal pours out the side everywhere. This is the same kind of thing that happens with regular cement and is why it does not make a good refractory, the trapped water (or water absorbed from the air) can (will) explode due to the water flash boiling to steam. Just remember, if/when it goes wrong in the worst way, it will be very very bad. (I hope you never have one of the sudden explosions) Also it's important to note that you need to use these in a relatively short time frame after baking so the plaster doesn't reabsorb too much moisture from the air. Don't bake and use months later or even a few days later without rebaking. I think we used baked plaster for lost wax when I did some silver castings maybe 15 years ago. Your new electric foundry should be a great tool to bake out the plaster with its temperature controls.

[@WaltSorensen]

I should also mention that the water in the green sand is different from the water in the plaster... green sand is fairly porous and any moisture in the sand is free to move around and go where ever it wants, whereas the plaster is a hard non-porous material and moisture has no place to go which is why the plaster can suddenly explode even when it has less moisture than the green sand. Note: Martin (olfoundryman) also uses water-based green sand... he talks about it in this video with his facing sand preperation kzbin.info/www/bejne/gmrUgWZvrph4as0

[@BigglesUK]

Do you get a single use out of these plaster feeders/vents or do you use them for multiple pours? i guess now you have your resin printer you may be able to make a mold to manufacturer them with less steps

[@silver760]

would be interesting to see how your foam patterns work with sand and sodium silicate casting sand mix/mould

[@lukearts2954]

very useful video, and as always, pimped with an awesome sense of humour :))

[@vogman]

Thanks Luke : )

[@brianl6192]

Forgive me if I missed it in the video but are these single use or are you able to re-use? Seems the only way to free the metal from the risers would be to break the plaster molds. A bit of an investment for single use no?

[@vogman]

Hi Brian. It is an investment, yes, but like so many things in life, you get out what you put in. They results speak for themselves. Whilst not totally reusable, I often find hollow section survive. I cast more plaster directly on to these and they work great : )

[@FloweringElbow]

@@vogman You got me thinking, I wonder if it would be potentially more reusable if the inner sides of the feeder were tapered. Maybe once the aluminium was hacksaw off the part could you then push it out of the feeder - or does it bond on tightly? Thanks for the cool videos, love em!

[@US-vy8up]

I ve learned too much from u Mr. Jeff. Not off course this year but in the future ı would like to see u and welcome u at my atolye in Bodrum/ Turkey. Please be my guest :)) Thank u for these treasure videos. I wish bests for u. Really good job.

[@vogman]

You are VERY kind : )

[@bullshoalshermit]

Hi. I enjoy your videos but wanted to address a potential issue with your sprue design. I saw it and said..."I'll 3d print the mold!" instead of using a candle and plastic sheet. Turned out nicely until I poured. Big blob of molten Al and the PLA in my mold (lost PLA process) went over my head and onto my back. Without a candle to "meltout" the sprue held a lot of moisture. I contend that this became a steam cannon...yikes. I have since tried to "burnout" the 3d printed sprue but it became brittle (270F 30' then 550F for 60'). 500F is the temp at which water is expelled from the chemistry...may be overkill. Once you start 3d printing, it's tempting to start making everything this way. Advice to those who watch and think like I did is to drive out some of the moisture with a lower temp bake. I haven't worked out a good "burnout" and my attempt made a total mess. Your low temp candle melt might leave the PLA intact (so no mess) and drive out moisture to prevent a steam rocket situation. Newcomers...expect the unexpected.

[@sammason8444]

Will the plaster hold up with copper?

[@ronyerke9250]

Vegeman? Ooooo kaaaaay.... 😈 Are the comments printed in green from your wife? Nice video. 👍 You'll have to ask Martin to be sure, but I suspect his baking advice has something to do with how fast steam expands and how easily or difficult the different substances can vent steam away. There could be a cracking or exploding problem. Keep your face shield handy if you're not going to bake your plaster fixtures as he recommended. 😨 By the way, I had some difficulty reading the comment that was overwritten by your watermark. This was in addition to the difficulty I always have because of my normally slow reading speed. 😞 Have you noticed all the little rubber "spikes" on new auto tires? That's part of the molding process. I wonder if drilling a few small holes into the seams of the mold box would help be rid of excess silicon or plaster. Happy Star Wars Day 🤓

[@vogman]

Hi Ron, I've had no explosions yet - just bubbling in the feeders and vents - which is exactly where I want the bubbling to take place rather than in the metal. I've also tried with just air drying and, if I'm honest, didn't notice any real difference, but I prefer to go above 100 just to be sure I get out the steam-makers : ) Trust me Ron, I'm a hopelessly slow reader and couldn't honestly watch one of my own videos without pausing, BUT it's seen so often these days, not just on YT but on TV, so I place the white comments there for those keen on the details and green comments there for folks who are happy to laugh little. Technically both lots of comments could be ignored - presuming I'm done my narrating correctly. The only comment near the watermarks is the safety notice I think...Naughty me. I'll have to look out for that next time. Interesting suggestion with the holes. I do plan on conducting some experiments with foam-coated plaster as so many swear they do it with success. It's never worked for me, but I'm happy to try again. Have a good one : )

[@DaveWard-xc7vd]

Do you have a 3D printer? I have 3D printed molds that make molds from which to cast parts.

[@vogman]

Excellent idea. When I posted this video I didn't own a 3D printer... but now I do : )

[@backyardmetalcasting]

nice work!

[@vogman]

many thanks : )

[@victor440_]

Thanks again great job 👍

[@vogman]

Thanks Victor : )

[@emiliogreenwood8190]

Did he say how long you had to bake it at that temperature

[@vogman]

I tend to let them air dry for a few days until they look bone dry. Then I bake them slowly, cranking up the heat gradually over about 4 hours. It's best to do a few to save the pennies : )

[@emiliogreenwood8190]

Cool 😀

[@vogman]

They work : )

[@josiahpolite9181]

can you re use the vent and feeder?

[@vogman]

Hi Josiah. You can often re-use them in part. Sometimes enough of a feeder or vent survives undamaged. Plaster of Paris can be added on to these to form a new vent / feeder, but partly using the old, saving on materials. I hope this helps : )

[@josiahpolite9181]

thanks, yea it does help

[@HDMIOT]

Wth vog why not make a two peice mold to do this, I guess u like doing this every time you need a few of these

[@vogman]

Silicone mould cost a fair bit and in honesty I don't do that much Lost Foam these days... plus I like to demonstrate alternative and cheaper methods where I can : )