Re-using lightweight kiln bricks as insulation

[scagliolist]

I had to close my school and I'm thinking I may now have the time to start planning a bread/pizza oven. I have several large ceramic kilns that are made of light-weight pale yellow bricks. Since they're designed to insulate an electric kiln, I'm wondering if I could use them to insulate around the dome. I might also use one of the lids as insulation under the floor firebricks. Thoughts anyone? (first time poster, long time lurker)

[Petter]

Sure, look in the end of this topic. Calculate your density and then pick your mass thickness and then the insulation thickness.

https://community.fornobravo.com/for...-do#post437680

[scagliolist]

Thanks, Petter. Unfortunately, my innumeracy is a problem. The lid bricks I have (pictured) are 9x4.5x2.5 Inches and weigh about a kilo. The liner bricks look like they are cut from the same size to make the octagonal kiln sides and have groves where the heating coils were. I'm not sure if the weight is right only because the bricks have been stored outside and its been wet lately. Is there a chart for optimal insulative value? I didn't see what I needed in the thread you sent. (or more likely, didn't know what I was looking at) Thank you for the quick response.

[JRPizza]

Hopefully david s will see this post - he seems to know more about kilns than anybody else here on the forum

[scagliolist]

Thanks, JR. Still early in the planning stage (late in the procrastination process). this forum is great. So many generous people. Hopefully, I'll be able to add something when the time comes. As an artist, my strengths lie in the final render process. I'm hopiing to use some swiss-style sgrafitto as I've done on my house in Roman cement (no portland, just hydraulic lime and aggregate) with integral color.

[JRPizza]

No problem - hopefully you will get some useful advise. If your bricks are firebricks, the link Petter gave you will help figure out how much insulation you should use for the exterior, but if they are insulating bricks then they need to surround heat holding bricks (I think you already know this).

[deejayoh]

Do a search for IFB or insulating firebrick. I believe others have used for insulation. Not sure why they are not used more commonly, whether it is performance, cost, or convenience? anyway, if you do have IFB, then re-using them seems like a great way to cut some cost of your build

[david s]

Insulating fire bricks from worn out kilns are ideal as you can often get them free from a kiln that no longer works. I've salvaged quite a few. It's best if you can dismantle the whole kiln and remove the bricks. They are ideal for under floor insulation. As insulation over the dome they are a bit more problematic because they don't conform to the curved surface of the dome. You could cut them into smaller pieces and set them over the dome, starting at the base and filling in between them with a 10:1 vermicrete. It will look pretty rough but you can work a layer over the top to neaten it out. They cut quite easily using an old handsaw. I used crushed insulating firebricks as an aggregate to create an insulating castable as the inner layer for my kiln with good success.

https://community.fornobravo.com/for...kiln#post14564

[Petter]

I get it to about 0.6 g/cm3. This is quite good. Use 4.5" + 2.5" as under floor insulation, I.e. One brick flat and one on edge for a total of 7" or 3x2.5", whatever suits you best.

About the dome, do what David says. 7" minimum insulation in total. No reason to go above 9" total thickness.

[scagliolist]

Thank you both Petter and David. I was thinking along the same lines as to using it to line the top, that it would be tough to fit the bricks. I was thinking of either adding them to the surface of the wet mortar as I finished the outer dome, or grinding them up into a sort of vermicrete mix. What I was unsure about is the thickness required underneath the floor and on top as compared to the ceramic fiber. So...7" under and same on top and sides? David S: the kiln project is very cool. Have two sisters who did ceramics, one still makes furniture pieces. I've dabbled, but no time to get into it deeper. Too many other art techniques to explore and refine. When we had our school, it was interesting to see how many people gravitated to clay work, both kids and adults. Something elemental about it. I'm the ancestor of the guy painting the cave walls.

[scagliolist]

btw, I plan on baking once a week or so, I'd say mostly sourdough boules, pizza once a month. My mom taught me to bake bread and make pizza when I was a kid, 7 or 8. Been doing it ever since, but never considered myself more than average at it. I just like making things...the process of it.(I'm an artist and craftsman. I prepare a lot of my own oil paints and media, work with gypsum plasters and roman cements, fresco, etc.) I'm looking forward to not having to beat up my electric oven baking at 500 once a month. I've got plenty of access to free downed hardwoods for firewood, mostly red and white oak on our property, so wood isn't a problem. I'd like to be able to bake a loaf with the 'right' temp and type of heat. Thanks again for the advice.