There's a Problem With Fire Bricks

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Fixing a problem with my heat treat oven caused by an issue with fire bricks. OK, it's bad engineering. But I'm going to blame the bricks.
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#metalcasting

[@PaulsGarage]

Want to learn sand casting using your 3D printer? I can teach you!: paulsmakeracademy.mykajabi.com/joinus

[@almalikisami4632]

Can I use them for pizza oven

[@dennisferron8847]

Yes! Cross-hobby knowledge sharing needs to happen. Often one group has solutions to problems the other group hasn't even considered. And although being into multiple maker disciplines can lead to a lot of need for space, it can also lead to efficient use of space: everything in my garage workshop has multiple purposes.

[@PaulsGarage]

I agree! And for space, there is never enough. It doesn't matter what you do, you could use more garage space

[@glasscaster3536]

Absolutely! I started as a ceramic sculptor and potter. After school I learned glassblowing. I was also interested in blacksmithing and metal casting. Through all of these ventures I only needed one oven/kiln. It is probably 50 years old and still works like a charm. I have used kiln wash and I fix any new cracks accordingly.

[@raymondjack]

There always a more efficient way to do things, it’s my goal to find them.

[@jamesnurgle6368]

I've seen over the last 10 or so years a lot of cross sharing between climbing, caving, highlining and even sailing and I think they've all benefited a lot from it and that'll be the same for this.

[@jeffbrownstain]

That's why a buncha hackers looked at your hobbies and said, 'yeah we can do that better' and we invented hackerspaces, putting one in every other city in the country.

[@profusemoose1488]

The pain of knowing there was an easier way but you just didn't do it that way because it involved having to talk to a human being... I felt that. lmao.

[@PaulsGarage]

Story of my life haha

[@miles11we]

I feel attacked

[@TrashTube-rt9jw]

I wonder if all is anti socials could deal only with each other how things would work…I bet the world would be very peaceful.

[@johnmccanntruth]

2 years ago I was watching you make the thing. Didn’t know you could get one cut to size like that. Depending on the price of course, that really could be a big benefit.

[@PaulsGarage]

Yeah you can get any custom shape you want. Not sure what the cost would be though

[@xlerb2286]

Years (decades) ago in college we built a small kiln with a removable top. The top had a steel angle iron band around it and a slight pyramidal shape to combat shrinkage. Worked pretty good for holding together over a few years of usage despite being built by a couple clueless students. Instructor gave us a grudging "it'll do" on the job. Which from him was high praise.

[@Canuck014]

You could use an adhesive specifically for kiln bricks to bond them together so it would move more as one. It would also help using ceramic wool on the outside surface for greater insulation. In our lime kilns we use ceramic wool, soft fire brick and then the harder fire brick on the inside for ware resistance. We also use a castable Fire brick but it’s very expensive. You should be able to find this material at an industrial concrete and brick supplier. Hope this helps

[@Boosted98gsx]

That adhesive stuff doesn't last at 2500-3000F, you have to use a castable refractory cement.

[@Canuck014]

@@Boosted98gsx I’ll look into that for you and find the product name I’m using and let you know what temp it’s good for. We us it in our lime kiln and it seems to last there

[@PaulsGarage]

thats a good idea for sure. this oven does have ceramic wool in the walls, though not all of them, for insulating. I keep thinking i need to add more where it's missing to boost efficiency a bit. It takes forever to heat more when it's above 2200

[@logicalemotion]

@@PaulsGarage Taking longer to raise the temperature is normal at high temps. The hotter it gets, the harder it is to get even hotter. This really starts becoming noticeable once you hit ~1800F, and then even moreso once you get up to 2200F-2300F as you mentioned. Especially since it looks like you're using electric elements instead of a burner (which will struggle at the higher temps). Electric elements will also burn out/wear faster the hotter the firing gets. My experience is almost entirely in pottery, but elements last considerably longer if they never go above Bisque-ing temperatures (around Cone 06 or ~1800F), compared to High Fire (Cone 10 or ~2345F).

[@retematic2351]

Use baby powder and water to make paste, if its not scented its the same stuff in powder form. You could also pulverize a brick to get the same powder, but that's tedious and probably not quite as fine grainwise. Can be used to fix cracks too.

[@shdwbnndbyyt]

Suggestions to prevent issue in future. One simple way would be to swap the bricks around every so many hours of use, so the shrinkage ends up being even over time. Now unless you use special alloy steel, most steel and pure iron have similar melt temperatures, cast iron having a much lower tmelt. 99.999+% pure iron has a much higher melt temperature, but it is very hard to obtain in quantities enough for rods... nice thing about having a career in chemistry for 40 years, you learn a lot of interesting trivia... Now there are metals that would withstand much higher temperatures without softening, but they are quite pricey. Another note is that your holes need to be loose enough for expansion of the rods, or you will end up with cracked bricks, especially when they shrink onto the rods.

[@PaulsGarage]

good points! the holes are mostly loose enough that i can push them in, but not tight enough that they fall out on their own. Since this was recorded i took the lid apart once and put it back together, and that seems to have loosened the holes enough that the rods can move a little

[@cdreid9999]

he just needs to build it correctly..like a brick wall..repying on gravity. And his new lid is going to fall apart quickly

[@jasondavis7567]

Actually you would want to use stainless steel rods and you can leave the holes fairly tight because insulator bricks are fairly soft and the little bit of expansion of the rods wouldn't effect it much as long as you mud all your joints

[@DDPhfx]

One small thing to note, the temperature on the rod isn't the full furnace temperature. There will be a thermal gradient based on the difference between the inside and outside and the rod will be somewhere along that gradient proportional to where it's placed in the bricks.

[@loganwilcox4037]

I don't know about fire bricks, but shrinkage has been a major problem in my life too.

[@PaulsGarage]

Its not our fault, it's just cold here I promise

[@matthewsharp1178]

Can’t believe I started watching you 5 years ago build this, it was what got me into this kind of stuff in the first place and melt my own metal, thanks!

[@PaulsGarage]

thanks for sticking around this long! and i'm always happy to push people into crazy hobbies 👍

[@lornablewettandlee504]

When I first switched on my home made electric foundry all the joints wanted to open up and fall the thing apart. I switched it off and built a cage around it, a bit like your rods, but external. When (if) I build my next (bigger) foundry, I will keep this idea in mind. A very neat solution.

[@PaulsGarage]

i think when foundry temperatures are concerned, everything is a temporary solution lol

[@lornablewettandlee504]

@@PaulsGarage So true! My "temporary solution" has lasted for two years and still works. I keep telling myself the next one will be better.

[@robertharris1748]

Potter here and this video was recommended. We've solved a lot of the problems you talk about in the first minute of the video! (Use fiber/castable refractory and your rebar solution is basically the Minnesota Flat Top kiln). I've always been interested in what else my kiln could be used for - although at ~10 Cu ft for the electric one and 30 Cu.ft for the gas one they're a bit big to fire up for small stuff. (Funnily enough the electric is a top loader (door is the lid - made of brick) while the gas kiln is a front loader (fiber door)).

[@soundsofglasswork6283]

This explains so much as a glassblower cause I've seen these built so differently depending on application in my field like most glass furnaces use the arches or the foundry style if the furnace is constantly hot vs annealing ovens which use less heat and less time hot are just cubes.

[@sadtown]

Absolutely agree on cross-hobby interactions. I do a lot of pyro stuff and frequently find myself gandering pottery and blacksmith resources because there's SO MUCH crossover. Shout out to all the ceramics guys keeping the cost of lithium and strontium compounds low. Love yall

[@PaulsGarage]

totally agree! People making greensand for casting are spending time grinding kitty litter into bentonite powder... you can just buy 325 mesh bentonite straight from pottery suppliers for cheap! It always pays to talk to other people doing anything, even if you think it's unrelated.

[@sadtown]

@@PaulsGarage Kitty litter is easily the most underrated household... Thing in my opinion! Need to plug a rocket engine? Litter. Chemical spills ( within reason)? Litter Gotta keep that cross-craft communication goin'

[@jonathananderson1728]

You can also use firewool, it's like fiberglass but for furnaces, use that as an inside layer and it should help take some heat load off the firebricks

[@caleb1345]

Wow, 2 years already... still got all the ingredients just sitting in my garage, unopened/unused... had wonderful plans 5+ years ago, but per usual, life happened. And so I chose to vicariously build with you, I'm very grateful you were willing to share along the way! Assuming life, well "actual life" doesn't stop happening anytime soon, I'll truly benefit from this shared knowledge, eventually, I'm sure, if I can just open the garage door... Again, thanks!

[@PaulsGarage]

Yeah I know what you mean, sometimes life gets in the way a lot. But depending what kind of life, it might be worth it

[@caleb1345]

@PaulsGarage So very true, as we've both seen. Been quietly by your side, and I've witnessed you make similar sacrifices, all in love. Long-Short... I realize you're busy, so thanks for the reply, even if the conversation ends here. I genuinely hope all is well with you and yours!

[@PaulsGarage]

@@caleb1345 Same to you!

[@senatorjosephmccarthy2720]

Thanks for the entertaining education on fire bricks. I'm building a forge now, and didn't know the bricks shrink a little.

[@PaulsGarage]

Glad I could help! And good luck with the forge!

[@jek__]

I love your style, easy sub. Informative with plenty of humor, just the right amount of editing splashiness

[@markmcgoveran6811]

Thanks for posting this and going over the subtle differences between two designs.

[@PaulsGarage]

Glad it was helpful!

[@jonnporter6081]

Back in the 1970s, I worked at a lead smelter. We used a coke-fueled blast furnace. We used some kind of mud to seal the cracks between the fire bricks. Got it on pallets of 50lb bags. We'd throw a few shovels full in a 5 gallon bucket and mix it with water; no special ratio. It sealed the cracks well. It wasn't adhesive, so it came off pretty easily when we shut down the furnace. For a small oven like yours, you'd be able to use a chipping hammer that welders use to chip the flux/slag off of welds. There's gotta be somewhere you and your friends can chip in and buy some of what ever that was. I never knew what industrial supply we got it from.

[@theshannonlimit1114]

The material you want is called Blakbond mortar made by BNZ materials. Also, not allowing for thermal expansion will spall the edges of the bricks, so looser band, plus strong mortar joints will work better. Many pottery kilns get destroyed because they are too tightly constructed. Gaps are your friend. Best of luck

[@PaulsGarage]

Thanks for the info! I think the place I get the bricks from gets them from BNZ. I'll look into that mortar. In my experience the kilns I've used definitely get looser and looser over time!

[@court2379]

I made my lids from fiber refractory board. It's more durable than wool, bit less than brick. However being a solid sheet, doesn't have this issue. You can coat the surfaces with kiln wash to hard face them to reduce damage, or repair erosion over time. Making a mount that prevents any sliding contact is a good idea, and usually allows for putting a bit of wool around the edges as a seal, which prevents wear and heat leakage. The mount also holds the hot door while you unload the crucible.

[@ablebaker8664]

Built a few kilns. Actually really surprised I only just stumbled on your channel since you do so much of the stuff I used to do. I like your idea about sharing experiences between disciplines. That's the way to learn new ways of doing crazy interesting stuff. Here goes with some of my experience with kilns. The biggest I've built was about 18 feet by 20ish feet. Basically big enough to park a 1 ton GMC Suburban inside with room to spare. Steel framed box suspended from a gantry. The gantry was on trolley rails. Took four guys to move it. It had two steel framed beds it could be dropped on so, basically... while one was firing the other was loaded and unloaded and serviced if it needed it. It needed it often. Structural mild steel really doesn't like glass firing temps and wool never seals up as well as I would have liked. The beds had 1/4" X 6" leveling blades bolted into the firebrick bed frame so that the top edge could be periodically lined up in a perfectly level plane a couple of inches above the fire brick surface. Then clay grog (basically non-scoop kitty litter) was poured in to fill the difference. That made it possible to use a screed to scrape the grog out perfectly flat and level. Economical to build and easy to maintain but not the most energy efficient beast. 200w 480v three phase power through mercury relay switches and a programmable controller. Ooph. Great fun to work around in the summer. Most were a lot smaller. 2' X 2' X 3' mostly. Great for almost anything. All of these used alumina foam firebrick on the inside and compressed ceramic fiber panels (basically space shuttle heat tiles) outside of that. There was a 2" L angle welded frame to buckle the firebrick together with threaded stainless rod to compress it together. Mild carbon steel threaded rod rots quickly and rotten threads make crappy fasteners. The ceramic fiber panels were fitted over that with a thin sheet of ceramic wool between to fill the space. Just adding that insulated it so well the outside was good and warm after a day long fire, but you could touch it without burning your hand. High fire nichrome coils were fitted into grooves in the firebrick walls and ceramic rod was run through the coils to prevent sag. Pieces of nichrome wire were used to fasten the ceramic rods to the walls (inside grooves) so that the coils were sitting about half in and half out of the wall surface. It's best to leave the coils as far into the kiln space as possible. The part in the groove tends to concentrate heat and when a coil burned out it would burn out facing the groove. The rods kept the coils from sagging so that wasn't a huge problem that they weren't stuffed into deeper grooves. Each of these had three coils for convenience but a couple of kilns I built like this used zoned heating so I could use a Terra cotta flower pot with a removable plug in the bottom drain hole, as a crucible for glass casting in the top of the kiln. A little high alloy steel rod and a ceramic cone set in the drain hole and after the glass had time to properly melt and fine (outgas) the rod could be pulled up gently by a cheap spring until the ceramic cone slipped out of the drain hole and let the glass melt flow into the mold. I even set up nichrome wire in random ladder-like arrays under the pot so that different colors of glass would drip down through it and become a bit better mixed but not fully blended together... Made awesome organic looking effects in the castings. Just measure the volume of the mold using sand... weigh the sand... put that weight of CoTE compatible glass into the flowerpot, plus 15%-25% for the glass that would cling to the pot and not pour into the mold... Ramp the kiln up so it didn't shock the mold and wait until the bubbles in the melt rose and mostly popped... pull the drain plug and start the cooling and annealing program. By using seperate controllers and zoned heating coils, the mold could be kept at a lower temperature than the crucible to keep the mold castable from breaking down while getting the glass melt hot enough to outgas and flow better. Hexagonal Boron Nitride makes a great high temp mold release for glass as well as a lot of metals and in case you want to put an actual top or side loading door on your kiln, this is what you want to use to lubricate any moving parts (hinges, pivots for a split top door, etc) It's a greasy white powder ceramic with the same molecular structure as graphite but much better heat stability. There... Probably as much as anyone is going to want to read from me for a minute. ✌️

[@Joe___R]

Another way to keep your lid bricks from shrinking would be to line the underside with kaowool. A piece of 2" thick should keep the bricks from getting hot enough to shrink.

[@JesterAzazel]

2:00 Funny you say that, because I was worried I was getting into too much at once. Forging, pottery, pyrolysis and distillation, composting. It all seems very exciting but it's just so much all at once. I appreciate all the videos you people make that I can watch during the work week and put into practice on my days off.

[@PaulsGarage]

There is no such thing as too much, only too little space and time 🤣

[@alexlindekugel8727]

agreed i got to talken with glassblowers and bronze smelts and learned alot from them. i still not good at maken molds for complex castings but learned how to make a furnce hot enuff to make molten steel with just 150 dollars in parts.

[@andrewgentner6169]

You edit and display your nerdiness/personality well. Very fun to watch!

[@PaulsGarage]

thanks!

[@acidblue8111]

I used to work for a metals recycling company. We mostly had refractory brick for the furnaces. When we line the furnaces we intentionally add 1 few mm in between the brick with a bitumen pads so when we ramp up the temp to ~1000 C (~1900 F) the pads would burn off. Since we ran the furnaces at more or less temp constant 24/7 until the next relining we don't really have issues with the lining itself (except for the occasional worksmanship or material infiltration issue). We do have shrinkage cracking on the spouts we use to tap the furnaces and yes we usually use pottery clay to patch up/cover up those problems. We found that low moisture clays worked best for that application

[@chaosopher23]

In between the bricks can be placed soft graphite gasket material. Exhaust system gaskets have a graphite ring, as an example. Graphite is one of those things you can't easily burn. It could save you on the electric bill and rate of cooling. I worked on one whose steel band was held closed with a turnbuckle on a spring. I might need a super-hot oven in the future, and any good-sounding ideas will be tried.

[@Repulseer]

Bless Phil Rogers soul. Potter here, not an expert but just by observation, when potters build their kiln, especially wood fired kiln (Those big ones) we use at least 2 layers of bricks. Usually a primary layer of firebricks followed by a backing layer of clay bricks. We also use ceramic insulation cloth between the layers to further insulate the kiln. That being said though, I have not experienced a kiln repair as of yet and cant comment much on the shrinkage issue as our kilns usually "Settle" over time and its geometrical shape usually solves any problems with potential cave ins and such. Edit : Definitely forgot to mention that ball clay is used as mortar too.

[@plainlogic]

I've worked in the steel Industry for years. My craft is in maintenance, not production. From what I gathered, keeping the furnace hot mitigates shrinkage of the refractory brick. The lentil entry to the reheat furnace fell in recently. They used metal to hold up the refractory, and the metal failed. The furnace had to be idled to ambient temperature for the reconstruction. Consequently, much of the other refractory had to be replaced.

[@zramirez5471]

For industrial heat treatment furnace design (giant methane pizza oven style) all our furnaces had height-adjustable doors that were metal frames with bricks inside of the doors; I would venture using this as the primary access for a non conveyor style kiln/oven/furnace would work fine too and eliminate a lot of issues like what you are dealing with. On the flip side you have some degradation of efficiency at the joints for that style door, have to maintain positive pressure inside and may or may not need some kind of ventilation to pull fumes from the entrance (like I said, we used methane so some different considerations)

[@d89taurus]

In the top 2 explanations of the month right here . I wondered how that worked.

[@rkalle66]

Paul, your tighting band does not give direct pressure to the inside bricks. The band is giving pressure only at the corners. Shorten the corner bricks and shape them to get some overall octagonal design so the band can exert some pressure to the bricks in the middle. Or just add a wegde to the middle ones between bricks and band.

[@WojciechP915]

I worked in an industrial foundry where the furnaces and heat treat kilns were larger than your living room. The furnace roofs are all made in arch shapes for this reason. A little shrinkage is taken up by the arch shape. Almost everything was high density fire brick arches supported by steel framework.

[@PaulsGarage]

Sounds like the way those large kilns are built. Always arched, steel supported. What did you make at that foundry? I'd love to hear about it

[@siiluviilu]

I dont do any foundry related stuff but i watched this whole video, love this guy

[@PaulsGarage]

Thanks! i appreciate it!

[@evilgenius97]

I learned from TKOR and now im here just before i craft it

[@Fusako8]

For my forge lid I go over all the joints with Kaowool reinforced refractory furnace cement. I use a furnace cement that comes in a Caulk tube just to make it extra easy.

[@PaulsGarage]

that sounds like a good idea

[@carentheblob]

i have built lids for my blacksmith forge and i used 3/8" Ceramic Hardboard coated in a ITC-100. ITC-100 is a coating that seals and protect the ceramic fibers, and it reflects/ re-emit the infrared heat as the heat up. they have held the heat for years, and have traveled from a dry climate to a humid one and are still very usable. my blacksmith forge uses 1" Ceramic Hardboard to insulate and the boards are extremely light weight.

[@PaulsGarage]

Good info! I'm getting some itc-100 actually, i've only ever used satanite up until now

[@ruperterskin2117]

Cool. Thanks for sharing.

[@greghumphrey]

Fun and informative. Thanks!

[@chadachwilliam5515]

I’m building a kiln this summer, as big as I can. I have as much clay as anyone could use in a lifetime. Tbh though, you can make your own fire bricks with plaster of Paris and sand, I don’t know the exact formula because I haven’t needed to make one yet. Fortunately for everyone interested, you can also add fiber glass to your mix to add some support in the mix. If you have ever seen the inside of a old coke oven, the walls and ceiling are basically glass.

[@weshowe51]

The blast furnaces I have seen in foundries (for steel) had rounded tops, sort of like a coffin lid. IDK what was done to the bricks to fit them, but essentially it was a long, gentle arch. That would stop the cave ins, and work with your square furnace.

[@AppaTalks]

I use ceramic wool with a steel shell :) Great video!

[@seanburnett7760]

Inspiring as usual, thanks!

[@PaulsGarage]

Glad you enjoyed it!

[@HughesEnterprises]

I used to be a professional potter. We had a gas fired kiln and fired in reduction. We used the entire natural gas service line that ran in the building for 4 burners and an additional 40K gallon propane tank run wide open on an additional two burners. We would fire to cone 11, which is hot for pottery. Total firing time was about 12 hours and then 12-18 to cool to ~350-500 degrees when you could start unloading and burning your gloves off. The roof of the kiln was built as a Roman arch. The floor and front door were on iron wheels on tracks so you could load and pull out the pots like a giant cart. The door was sealed with kaowool which is basically synthetic asbestos that hasn’t been banned yet. And if you pump in enough gas, any air leaks won’t matter. But kilns don’t last forever and it needed to be rebuilt every 5-7 years.

[@dcsensui]

Thanks for your entertaining presentation. I saw a few videos where they were making their own firebrick with a mixture of refractory cement, vermiculite and sand. With that you can cast a custom-shaped piece of any size. Perhaps include reinforcing iron within the piece?

[@PaulsGarage]

That's an interesting idea! I'd be worried about the sand and vermiculite, i've heard those can vary a lot. I'm planning on getting some Kast-o-lite 30 and make some stuff, maybe cast a lid or some bricks, but that's a plan for when the budget is a bit "healthier" lol

[@gbgman97]

When I built pottery kilns many years ago we pinned them together with stainless steel rods. Snip them with big side cutters and instantly get a perfect bit. I never thought to ask "why stainless?" I only did it for a short while and it was just what they used.

[@PaulsGarage]

that's interesting, thanks for the info!

[@colinwilson210]

You could also use the ceramic fibre insulation that comes in rolls, easy to handle and form into shapes

[@fredio54]

Consider longer threaded rods and tighten onto springs at one or both ends of each so the tension remains more or less constant with expansion and contraction. My 2c.

[@Michael-ei3mh]

Bravo for making you own kiln/ furnace thing!!! Gaps can help you. Reduction kilns aren’t that tight. They get the reduction by burning more combustible material than there is oxygen ( extra gas,wood, or oil )There is always positive pressure in the kiln so small gaps don’t matter. A sagging lid isn’t so bad and it looks like yours was a far way from falling in. I’ve seen way worse that last for 20yrs in that condition. Kiln manufacturers use a type of kiln mortar and seal the inside of the lid and between each brick as well as using octagon shaped tops to keep compression more equal like you said. Bravo for you ingenuity and exploration!

[@PaulsGarage]

Thanks! The bricks were definitely far from falling in for sure. The way i designed it the bricks could just be stacked on top without falling in, but the way the inner parts shrank I couldn't lift them off as one. The mortar is a good idea but I think I'll still avoid it for now just so I can change out bricks or use them for something else if I get a hard board lid or something

[@Sole_Samurai]

adding any kind of insulation to the bottom of the lid may be enough to help reduce the issue and expand the life cycle of your lid.. I don't remember exactly what insulator we used in the forge shop I worked in but I do know we had massive steel doors with only the insulation just rawdogging the heat. They lasted a while as long as the insulation remained

[@joelcannon58]

I am casting my own bricks and molding a 1piece rocket stove using chicken wire for rebar. Recipe includes refractory cement, sand and mostly vermiculite and perlite.

[@TimeSurfer206]

Frankly, it was both bad engineering, and the bricks. When I make my kiln I'll be sure to "dome" the top. And do wedge-shaped bricks for the sides with compression bands that can be adjusted. And thank you for this info. You helped me a lot with these few words.

[@PaulsGarage]

domed lids are ideal i think, wedge shape is good too. My foundry furnace lid isn't domed, just wedged, and there have been no problems

[@tombrown879]

I wonder if you could mix up a batch of " Star Lite" material. and put it on a thin steel sheet of steel even a piece of wood for a lighter lid. It will shrink and will need some patching at first but after it is burned in, it is pretty stable. It just won't work outside where it could possibly get wet. It is pretty amazing stuff. I have used it in place of Satinite many times for gas forges. Something to look into at least.

[@PhD777]

Outstanding video! 👍🏻🎅👍🏻 Glad I clicked, liked and subscribed! 😂

[@cameronvanatti6629]

I'm a pyro, if anyone needs me for something This is the first video of yours that I have watched, and I'm dying at the words on screen

[@PaulsGarage]

Welcome to the pyro party! I think everyone who does this stuff secretly just wants to burn and melt stuff for fun

[@cameronvanatti6629]

@Paul's Garage I had a piece of copper pipe I found as a kid that had a fitting on one end and was long and curved at the end. It looked kinda like a smoking pipe. I would take dried grass and pack it into the fitting side that curved up, dip it in gasoline, let it drain out so it was just soaked in the grass, then light it with the fire pit and blow through the other end, sending 3ft flames out the other end. I miss those days, I will make a new pipe for it one of these days

[@johndees967]

Bud!!!!!... that was SOOOOO interesting!!... never cast a bloody thing in my life.. with heat i mean.. but your presentation was so good.. i stayed and watched it all. Good job on the presentation.. and very good skills there man!! Liked it a lot!

[@PaulsGarage]

Thanks John I appreciate it! You cast stuff without heat? Like resin? How do you like that? I want to try that at some point

[@gregorychaney7604]

Another great video! Great comment about masonry arches. Cheers from Alaska

[@PaulsGarage]

thanks! masonry arches are pretty awesome

[@gregorychaney7604]

​@PaulsGarage I'm thinking about sending you some zinc ingots (pretty close to pure zinc, not alloys). At first I was dismissive of zinc but it doesn't take long to melt and it pours beautifully. At human temperatures, it is a lot like cast iron but shinier. Are you still at 1818 Milton Ave? Or did your address change when you moved? Cheers from Alaska

[@PaulsGarage]

That would be great! Milton Ave is a post office, i have a P.O. Box there, it's still there so that works. Just let me know if/when you send it so i can check the box. I'm not very good about going there often

[@gregorychaney7604]

​@@PaulsGarage The ingots are in the mail. They should show up in about a week or so.

[@a-yates]

I can geek out on refractory block 😂

[@1noryb]

Steel rods - good start, if you shape them into an inverted arch inside the bricks and then post-tension them (steel stretches like a spring for when they are cold and larger) if the bricks can take that much stress. Post pensioning them from that inverted arch shape also pulls the outside bricks down, or the inside bricks up. And as pointed out mild steel may not be the best steel to use.

[@PaulsGarage]

That sounds pretty awesome but I'm not sure how I could drill the hole like that

[@unrepentantbastard9088]

@@PaulsGarage tig rod. buy a pack. W lasts in hot applications longer than mild steel. Dowel them bricks like tabletop boards =)

[@ivanyes8075]

Very nice 👍

[@danielcarter7657]

Kaowool is a really nice insulation for that application just provide a support frame with handles

[@PaulsGarage]

Kaowool is great. This oven has a bunch of it in the walls for insulation, you just can't see it because it's all covered

[@johnydl]

I never thought this bit of my brain would ever find function but for a little while in my teens I helped with the manufacture of electric ceramic furnaces for industry, they are almost always double skin with the bricks and the layers are deliberately offset as much as possible, so the corner of the bricks at the back is in the center of the bricks at the front. Takes a little more engineering up front but I think it might have been for this reason. I also remember refractory cement only being used on the outside layer and to bond the inside to the outside but the brickwork wasn't my job, I was wire brushing and painting everything metal red then enamel

[@ryszard8779]

wonderful video x

[@ryszard8779]

I see you liked my comment and I wanted to clarify that this video came up in my recommended and even tho I don't do any very hot box crafts it was an interesting watch and I love when people just talk about stuff they're interested in :)

[@Hydrosized]

I just went for a hot box because of you! Lol

[@someweeb3650]

You should put a little block between the band clamps and the bricks, it will absolutely put pressure on the middle ones. Could also use them as nice handles ig

[@denisdespins1127]

I actually love aluminum borro silicate brick. I cast bronze hammer heads, (so far)...super easy to mill and cut.

[@PaulsGarage]

they are really easy to cut, agreed. After a while the abrasiveness of the dust wrecks the saws, though. that's what home depot saws are for lol

[@FeralMoonDesigns]

Loved the video man! Enjoying watching your production evolve! Also I really want a kiln lol. I need a workshop...

[@PaulsGarage]

Kilns are awesome, you never know how useful a controllable oven is until you start finding uses for one. The only issue i have with this one is the size, but I have some bigger kilns if needed too

[@JointerMark]

Build a kiln! The bricks are easy yo work with, just don't inhale the dust. There are a couple of videos on the electronics to control the electric heating elements (I patterned mine off of Veg Oil Guys kiln). The parts aren't prohibitively expensive. I would advise buying a good quality SSR (solid state relay).

[@mindofmadness5593]

Had not seen you in awhile, nice to see you seem to be doing well. I was around when you built that oven. Ended up going withthe propane tank/KAO Woll deal. Not run it for a bit-new property, getting things going but I now have a workshop and pghoto studio. Will see how mine holds up in a few weeks-have to order a new crucible because my others got left behind [[sigh]]. Good to saee you tho Amigo.

[@PaulsGarage]

Welcome back! It's good to be back making stuff again

[@a-yates]

They dont shrink per say kinda but more important is they expand when heated andcontract when cooling so if you make an adjustable clamp for your furnace you can tighten when you cool and loosen when you fire have to look at the specs on expansion rates for the brick you chose if your using an exposed flame you want the brick to be a hard brick or a superduty

[@garykurtz7787]

Thanks m8, good info.

[@PaulsGarage]

No problem 👍

[@deepashtray5605]

Refractory blanket works well for lids. It's light weight too, but it helps to be rigidized. An area the size of your kiln there would be quite affordable. The plus side is it's flexible, affordable and can be rapidly heated with no cracking issues. The down side is the dust is extremely irritating and potentially carcinogenic so it's a good idea to seal or rigidize, and it cools down very quickly compared to fire brick which can be an issue if you want to control the rate of cooling. I suspect you're probably well versed on the stuff. 304 stainless steel works very well for those kinds of temperatures. The issue with steel, like the threaded rod, is that heated iron will react with any CO2 generated by the firing and cause corrosion which can damage the bricks, an issue with both electric and gas pottery firing, and if the steel is galvanized the zinc fumes are toxic. 304 stainless has a ridiculously high melt point though at high temps it will oxidize but without the corrosion issues you get with iron. I come at it from a pottery perspective, now building my 2nd kiln, and could not agree more about sharing info between crafts as I've gleaned most of my deep in the weeds detailed info about gas, gas burners and construction materials from DIY forge builders.

[@mcdls5]

You're fun to watch.

[@PaulsGarage]

thanks!

[@TechGorilla1987]

@1:07 - They already make such a device for kitchens. It's called a turbo-chef oven and it's exactly as you described.

[@equesdeventusoccasus]

I used to work for a company that made cremators. They recommended to their customers that they rebuild the cremators every 10,000 hours. I also worked for one of the world's largest fire brick & kaowool manufacturers, and a large part of their sales was bricks & kaowool for rebuilds. These bricks are only good for so long, then they need replacement.

[@PaulsGarage]

I talked to a potter in Korea (one of those pictures was his kiln) and he said his kiln was the oldest in Icheon (a city of potters), at like 40 years lol. The place has had constant pottery production for a thousand years and the oldest kiln they got is 40! These temperatures make everything temporary I guess

[@jimintaos]

A number of years ago I built a large glass kiln that had a 6 foot by 9 foot bed-yup 6x9. I used HD board which comes in 2foot by 4 foot by 1 inch panels. Over that was several inches of fiber blanket. This kiln had a roll out bed and opened on the short side. So-how to support a flat kiln roof that big. My solution was to have all of the support structure across the top, above the insulation so I wouldn't have to deal with expansion and spalling of the steel when it got hot. On the inside of the kiln I had a series of stainless steel rods that were free floating and held in place with nichrome wire that looped over the steel support structure and under the stainless steel rods and then back up to the support structure where it was tied off. This worked quite well for several years. I have also found that long, coarse thread drywall screws work really well. You can't expect to ever use them again but with a stainless steel fender washer they will hold the bricks or the HD board in place wonderfully. My current foundry uses soft brick with a coating of satanite for the walls and two layers of 1/2" HD board for the lid. No issues. The HD board is drywall screwed into the firebrick.

[@PaulsGarage]

That sounds pretty awesome! 6' x 9' is incredible. It was for firing glass? like slump molds and stuff? What kinds of temperatures does that require?

[@jimintaos]

@@PaulsGarage I originally built it to do a series of panels for a restaurant that were 5' x 8'. Multiple layers of plate glass fused over a freeform blanket mold. Generally, fusing multiple layers of glass at 1550 F. Slumped panels were below 1250 F. The challenge was that I had three heat zones that I controlled with a Digitry controller. Go slowly to 1050 F then as fast as possible to the working temp, Hold for ten or 15 minutes and then dump heat down to 1050 F and go very slowly back to room temp. Usually a firing was around 36 hours from load to unload.

[@iainburgess8577]

Tig welder tungsten rods. High temp, rigid, not massively tensile, but great for alignment. Easy to find, and because it's a very common mass production part, pretty cheap. Random idea inspired by this vid.

[@toutenmagma7140]

i got impressed when you said 2000 degrees, i assumed you meant Celsius lol, i understood my mistake when you said it doesn't get hot enough to melt steel

[@PaulsGarage]

2000 Celsius would be pretty intense!! I don't get THIS oven hot enough to melt steel, though i probably hit cast iron temps on occasion. I have a different gas powered furnace that might be able to do steel, though.

[@iancormie9916]

A) Use basalt rod. It will have a coefficient of expansion that is much closer to the fire bricks. B) Put a spring on the ends of your rod to maintain tension. C) cast a 1 piece top for your kiln. Recipes for thermal bricks are readily available.

[@helvetiaresearch9973]

VCella makes kiln lids with bolts through them to hold everything together.

[@jasblick9984]

I built a forge out of a new paint can with a lid, a large soup can, and a small fan. Well that and I made a perlite and homemade water glass mixture for the refractory. Some low temp ramp up temps, then worked the temp up to cure the refractory. The whole thing it runs on for testing is sticks and twigs. The whole thing gasifies and creates biochar. I need to add transducers to turn the excess heat into electricity

[@nosidenoside2458]

IDEA: take the lid apart, and then put the shrunken sides of the bricks on the outside and the unshrunken bricks on the inside.

[@PaulsGarage]

That what I did, yep

[@reverendfawkes6138]

A buddy of mine who used to build heat-treating kilns would cut a channel in the sides of the bricks that would be deep enough [and wide enough] to accept half the width of a 1/4"x1" flat bar. That bar would slot through and be kept in place by the strap. Maybe this is something you could try, because the threaded rod will only hold the bricks along a single axis. It'll still gap out in the middle.

[@hellawacked]

Should add we don’t perfectly cut bricks to deal with the opening the door problem as glassblowers. We just replace the door. You figured it out but for a top loader you’ll need to reinforce the bricks. You also need to use cement. Honestly build a better structure for the whole thing with replacement of the bricks in mind. For a furnace I have a few designs that are nice I can share. If you want something more flexible a couple years ago I thought up a design for a front loader with a crucible hole on the top.

[@jasondavis7567]

If you want to go the super cheap route you could always make your own top out sand and plaster of Paris that way you can make it custom fit for your furnace

[@slicktires2011]

I recently built my third electric furnace and have many of these issues too. I thought about sticking a metal rod through the lid, but worried about differential thermal expansion cracking the bricks. What i did was: - carve a groove on the exterior perimeter of the lid, and put a metal square frame there. The frame has some clearance to move around, but this clearance is much smaller than the grooves are deep, so thereś no space for the bricks to slip and fall, even with gaps between them. - the bottom of the lid has ceramic wool insulation. This helps a lot in keeping heat away from the bricks, so they don´t expand/shrink so much, and also seals the gap between furnace and lid, so it helps with efficiency. The wool insulation is glued to the bricks with sodium silicate, and i also put some steel staples made from fire. The top of the lid is barely warm to the touch when the furnace is melting aluminum, except in the air gaps between the bricks where it gets hotter.

[@PaulsGarage]

that's a good idea too. I'm also worried about the expansion of the steel rod, but I think it will be ok. The rod won't increase in thickness enough to cause problems, but it could increase in length quite a bit, so it's just sitting in the groove. It's free on both ends to expand out of the bricks if it needs to, nothing is holding it in. Time will tell, though. I'll have to use it a bit.

[@Hellsong89]

@@PaulsGarage Might i add that maybe use basic round stock, not treaded rod as it looks like you used. With this there is more supporting surface area and no treads to eat into brick when there is thermal expansion in the rod.

[@untermench3502]

I like making my own mix, but getting the proportions right so that it doesn't shrink and crack is a problem. Most of the components have a negative shrink, but if you add Lithium Oxide, which has a positive expansion, it cancels out. It takes about 5% Lithium Oxide to balance it out. You may have to experiment a bit, but it works.

[@Pystro]

You could strengthen the lid by changing its shape: Cut down the length of the outside 2 rows of bricks (You only have to shorten one of the 2 bricks on the left and 1 on the right); or extend the length of the middle 2 rows of bricks. That way the band clamp pushes on all 4 pairs of bricks from the front and back, which effectively forms 4 full-length lintels. And the pressure from the side then only keep the 4 lintels together. Or if you view it from the other direction, each column of 4 bricks is pushed into a full-width lintel. But currently the force is only applied on the outside of that lintel. You could fix that by adding a spacer piece between the band clamp and the inside ends of those lintels.

[@PaulsGarage]

That's a pretty good idea. The lid is square but the opening is rectangular so there's some room to spare if I shorten the outer bricks

[@alliwantedisapepsi1492]

I made my own fire brick. Something like 45% fire clay, 45% bentonite and 10% very fine sand (120 grit?). The mold for the brick was circular so the burner would have a clean path around a crucible. Let it dry for 7 - 10 days, then slowly bake in the oven from 150 - 350 for 2 - 3 hours. Make a old cedar fence lattice on the ground. 4 or 5 layers thick. then place bricks on top of it. Add 4-5 cedar layers on top of the brick. Light it with a match and watch. when it starts to get really hot cover with more fence to trap the heat and burn slower. This doesn't fully cure the brick but it gets it close. Then build a kiln and fully cure , with the burner. Hit yellow colors inside the kiln. It's held up very well for me. Wrap with fire blanket to stop air flow. I cant promise it's better than commercially available brick, but you can make a cheaper kiln to your exact dimensions to properly fit your crucible. For best results don't make bricks thicker than 1 1/2" x 1 1/2". or the center wont fire properly. That's why I wrap with a fire blanket. After firing I sanded the brick using a 2x6 wrapped with sand paper. With calipers I could sand the bricks to within .020" to minimize gaps. For final assembly make a clay slurry and use it as mortar. My lid was only 1" thick with a hold cast in it, but it works well. It is smaller than your 18" by 24" lid, but it was cool to make a kiln from scratch and see it work. Cheers.

[@Mrshotshell]

Adding something under the hose clamps on each side across the seam where the threaded rods are should help move some clamping force to the sides instead of just the corners. Stainless steel threaded or smooth rods would probably be a good idea to avoid corrosion and any possible fumes from the zinc plating

[@PaulsGarage]

I could probably fit something under the sides for tension, good idea. The band clamp doesn't sit flat against the sides

[@asteriskman]

who is this man and why is he so casually hilarious? is he my new ave?

[@PaulsGarage]

I can't be the new AvE. I lack his Shakespearean grasp of creative foul language, for one!

[@Mr850man]

First time seeing your channel, the comments on yellow letters are great lol

[@PaulsGarage]

Thanks!

[@jpolowin0]

A few decades ago, an acquaintance of mine and I tried iron smelting, and built our smelter out of alumina kiln bricks, mortared with clay from my garden. That was a terrible mistake. At the yellow-white heat inside, the clay dissolved into the alumina like acetone into styrofoam. The structure developed severe cracks. After the first firing, it still seemed to be reasonably stable, but during the second run, it began to lean and seemed to be on the verge of collapsing.

[@PaulsGarage]

Oh yeah iron temperature is insane, and most clays will melt a couple hundred degrees below iron temp. A lot of minerals in clay will also turn into a flux above 2000f, so it will just destroy everything lol good thing you survived!

[@jameshaulenbeek5931]

There are many materials that would work - you can make a metal lid with layers of some type of insulating blanket material, even coat the wool with a refractory cement to help prevent degradation. It's not cheap, but it's most likely an expense that would last for many years, possibly decades, depending on materials used, etc.

[@deanharris7149]

Idea for the lid. Cut the all thread so that it sticks out 2”-3” of the bricks. Put a washer against the bricks, a spring, capture the spring with another washer and nuts on each side.

[@mdp4440]

I was a potter for 45 years (retired now because of hand issues), but I've built a number of kilns. I've found that different manufacturers produce brick with different qualities. I didn't like the chalky Babcock Wilcox bricks but preferred the A.P. Green product. A Nichrome rod might have a better heat resistance than your steel threaded one. I fired to cone 10 (2381° F)

[@allangibson8494]

Stainless steel has a higher heat resistance than carbon steel. Nicrosil (thermocouple alloy) is available in metal sections too.

[@PaulsGarage]

thanks for the information! I have a few kilns from different makers and I think you're right, the bricks are very different. All the ones i've built used 2800f rated light bricks from armil cfs, but i think they sell bricks made by BNZ? i'm not sure. I think a nichrome rod would be perfect, i just didn't have any on hand. Sorry to hear you quit pottery because of hand issues. I haven't made any pottery in a little over a year because I moved and had another kid, but I miss it a lot. I only fired to cone 5 or so but I was using a local clay I dug up here and glaze made from another local clay, and above cone 5 I started to get problems with the glaze and around 6 the clay body started to fuze to the shelf. It would slump at 7, I found that out the hard way haha!

[@nostalgicmusicbox]

I used high temperature mortar for mine. I'm not honestly sure if it expands or contracts at any different rate. So I don't know if there's going to be cracking issues. But I didn't have any. Granted, it's been years since I've been able to use a forge. But it was able to get hot enough to forge weld. Anyway, maybe something to try. Might not work for your application. But it worked pretty well for what I needed it to do.

[@PaulsGarage]

High temp mortar looks like good stuff. It would have to expand with the bricks I would think it it would all break apart?

[@nostalgicmusicbox]

@@PaulsGarage I didn't get that issue but I was also using kaowool or super wool? It's a ceramic wool made for high temperatures. It retains teeth really well and also doesn't have issues with expansion. But you do still need the brick around it. One thing that I've used was to make a dome out of the wool and coat the outside in high temperature mortar. Just as a structural foundation. And then let the hole in the top so I could kind of use a coal forge, almost like a directional blowtorch. This is all just experimentation I was having fun with. That might be worth looking into. Both of those you can get for not too much and in small quantities playlist before you invest heavily into.

[@acbenepe]

Old geezer craftsman here, I just have to complement the prominence of the fire extinguisher on your tool shelf.

[@PaulsGarage]

You never know when you need one! I have 3 of them in different locations, that one in the video is in the middle of the L-shaped shop at arm height for easy reach. i considered painting the shelf red, too to make it stick out more, but then it would cover up the dovetails! Not a bad idea, though, because i suck at cutting dovetails and they look terrible up close 😂

[@farmboycharlie6543]

Brilliant idea castible refractory

[@PaulsGarage]

I've used that stuff and i'm not impressed, but i didn't use one called Kast-o-lite, which i hear is the good stuff. I'm ordering some soon to use fixing up the foundry furnace, so i'll check it out.

[@farmboycharlie6543]

@@PaulsGarage Don’t remember the stuff I was using like the bricks it is application critical. Have always dealt with a refractory dealer that’s all they do is commercial. Heat treat ovens forges kilns . But I’m in a area with heavy equipment manufacturers . Good luck in your ventures. I’ll be watching

[@adamorick2872]

Make lid larger then kiln, with them having a 45 degree edge on inner bricks that meat outer bricks. However make end of outer bricks about 1 inch farther out then inner bricks