Making Lightweight Bricks for a Kiln

[Harry]

As I mentioned in the Lil' Scrapper thread I have just had the experience of working with Kast-O-Lite 20-45 and I am quite pleased with it so far but it is as yet un fired. My cost was $0.85 lb and it comes in 25 lb bags that work out to right at 1 cu fit a bag. I cu ft will make 18 3 x 4 8" bricks so cost would be $1.20 per brick plus time of course in firing them.

Just wondering what kind of pricing to expect in lightweight bricks if they are purchased ready made and would these be better or inferior to commercially available bricks. Anyone have experience with these or tried making their own? I bought a bunch of used bricks for a quarter each a year or so ago but they were the dense bricks and are currently serving as the floor for my foundry area. The light bricks would be much better for a kiln I would think since being insulated better it should be easier to maintain temperature in the kiln. Also kind of thinking I could make some custom shapes for putting together a domed top that would be self supporting.

[HT1]

According to this reference, the lightweight firebrick would be twice as insulative as the hast-o-lite
http://mikegigi.com/refracto.htm

and if you go to
http://www.atlanticfirebrick.com

they have a pricelist , though they are higher then what you are getting, but it is a good generalization

I'm still jelous of all those good deals you seem to get

HT1

[Rocco]

I've had a kiln made of lightweight bricks and my current furnace is made from a lightweight insulating castable similar to your Kast-o-lite and the two products are very different, the bricks are much less dense and soft enough to be cut with woodworking hand tools, the castable is similar in appearance and texture to concrete, calling it lightweight is a bit of a misnomer, it's only lightweight when compared to other castable. As to which is better, that depends on which properties you value most, the bricks are a much better insulator but are rather fragile, the castable on the other hand is tough and will take a fair bit of abuse.

[Harry]

HT, I didnt think $0.90 was such a deal. Last castable I bought I think it was closer to $0.75 a pound. I am fortunate that I have supplier within a reasonable driving distance. I kind of thought it would not be as insulating but certainly better than the heavy firebrick I have.

Rocco, thanks for the insights. At 18 bricks to the 28 lb cu ft weight it would mean around 1 1/2 pound per brick which I would call pretty light but I know what you mean about the real lightweight bricks being like air. I think I like the idea of these being a little sturdier. At just over a dollar each it could make a nice big kiln a reality a lot sooner than buying brick.

[mite5255]

if you had a mould for what ever size brick you needed you could try mixing the castable with washing up detergent mixed with water to airrate the mix, you then should end up with a lighter weight brick . In years past when I use to do heaps of cement rendering we use to use a admixture to our render to make it fatty so it was easer to work and it put every tiny air bubbles in the mix, it may work for light weight bricks

Mike

[Harry]

That may work really well with this stuff Mike. It is amazing the way it holds onto the water, I mean this is 50/50 mix and no water drained out of it which shocked the hell out of me. I thought no way 6 gallons of water was going to stay put once placed into the forms but it did. Maybe make a bubblier like those used for sand to get air into it.

[mite5255]

That may work really well with this stuff Mike. It is amazing the way it holds onto the water, I mean this is 50/50 mix and no water drained out of it which shocked the hell out of me. I thought no way 6 gallons of water was going to stay put once placed into the forms but it did. Maybe make a bubblier like those used for sand to get air into it.

Harry when you say no water drained out of it, I think thats what we use to call bleeding http://www.encyclo.co.uk/define/Bleedin ... oncrete%29 I would assume that they would have something in the mix to stop it, the admixture that we use to use bycol http://www.diyinfo.org/wiki/Diggers_Bycol it would help prevent bleeding and segregation

[Harry]

Thats it Mike, usually when you form up concrete and pour walls you will get water leaking at the bottom and joints and concrete has a much lower dry/water ratio... this stuff was 50/50 and held its water which is what amazed me because so much of it was just water.

[mite5255]

Thats it Mike, usually when you form up concrete and pour walls you will get water leaking at the bottom and joints and concrete has a much lower dry/water ratio... this stuff was 50/50 and held its water which is what amazed me because so much of it was just water.

50/50 is bloody amazing

[Harry]

Thats the point I was trying to get across, 4 gallons of water to a bag of the dry mix which is just about the same in a five gallon bucket. Mix it up together and it hangs onto all that water somehow. Get the furnace hot and it comes out though