matthew boersma wrote:hey all, i am about to cast my core in a day or so. i am using kast-o-lite 30li for the refractory cement. i have already built molds out of plywood for both the core and riser. my molds are measured out to be about 1.25 inches for the outer wall thicknesses. my question is.. would you think 1.25 inches is a good enough thickness(or should i really go bigger? i have a vibrator unit so i am looking to get very solid casts. also i have noticed after squishing in my riser innards foam part that my riser dimensions are likely to be about an 1/16" more on at least one of the sides. any perceivable issues there (i was thinks at least it isn't much of a difference and not smaller)? any thoughts?
I do not have experience with casting, although I am making a mold right now. I would think that 1.25 is a good thickness, like the "split" fire brick.
I would think that it is not good to make it too thick, as that could cause cracking with the expansion. But that is just my guess.
One think you may want to do is to cast a small brick to as a test to get familiar with the Kast-o-lite, and to see how strong it is.
I notice you are casting a square riser. Peter's original model used a vermiculite board, as do the Dragon Heaters. The Lowes in this area sells vermiculite board in 36 inch squares at 3/4 inch thickness for a good price. (If you have to get it mail order, it is very expensive, since they have to make a special crate to ship it.)
I think the vermiculite is a better insulator. But if I was going to actually cast the riser, I would make it round.
But again, I don't have experience with this.