Research

I'm a big fan of ceramics books. The one drawback of my book library is that a lot of it is dated material in classic ceramic books. One such thing I found was Jack Troy's book Salt Glazed Ceramics. The book covers how to make salt glazed ware, and salt kilns. In his book he used Portland Cement because the newer alumina refractory cements weren't available when he wrote the book. Toward the end he discusses the ongoing research in castables which he discusses adding alumina to the cement in ratios. Well I did a lot of reading and found many articles talking about castables and several covered this in detail claiming that adding alumina oxide or alumina hydrate to a cement would not work.

I did a lot of reading on castables and refractories. I read research papers books, blogs, discussion boards, websites, technical data sheets etc. All of this research led me to a basic formula for a medium to light castable cement which was mentioned in my last blog consisting of, 2 parts fire clay, 2 parts grog, 2 parts saw dust, 1 part cement. For this recipe I chose to use Ciment Fondu because of the fairly reasonable price of $44.00/bag-94lbs.

We used this product in my mom's backyard oven. I have some concerns about the oven because the castable will shrink considerably and my parents decor design has a flaw. They wanted to use bricks on the outside and we'd already decided to use a castable cement. Well the cement is going to shrink some when I fire the oven off the first time, and the bricks will not shrink. This means that the interior will shrink away from the bricks and there will be a gap. This would not be a problem except we used a sprung arch design in the top of the oven for maximization of space. As it shrinks it can become unsupported and crack, or even fail. I'm going to strap the thing together with steel support braces prior to firing, but who knows if it will work or not... The one thing I could not find (and did not test because of time constraints) is the shrinkage of this castable upon firing. I guess I should hurry up and fire off the blocks I've made.