Hello, I am planning on removing the foam form this weekend. If I end up with some pin holes, air pockets or larger holes on the inside of the oven, would there be an issue if I used a little of the black high temp mortar caulk that comes with the Mattone Cupola kit, or would a tube of Rutland’s Fireplace Mortar (comes in gray), be better in this instance for these holes, instead of buying a whole tub of Sairset?
I’m going to leave some of the response on this to @BrickWood, but I presume when you’re talking about “pinholes” you mean all the way through from interior to exterior. For those mortar caulk is fine.
I’d stay with Sairset for the larger voids you’re describing. I found 15 pound tubs of it readily available online for about $20, versus the $90 and up you’d pay for a full 55 pound tub from Harbison Walker.
Unless you know something about your casting that leads you to have some bad feelings about pulling out the mold, this whole discussion may be academic. Let’s hope for the best, Andrew! And let me know how it came out, either way.
Sorry for the late entry on this…
HIGH TEMP MORTAR / TUBE - If the pinholes are smaller than a pencil eraser, you just need to blast some High-Temp Mortar in there. If the pinholes are on the EXTERIOR of the oven, don’t waste your time. Those small pinholes will NOT effect the performance of the oven and you will be covering the exterior of the oven w/ Ceramic Fiber Blanket.
SAIRSET - If the holes are larger in size (larger than a pinky nail, but smaller than a thumb / first knucle), you may want to use Sairset High-Temp Mortar and a putty knife.
CASTABLE REFRACTORY - If it’s larger than a thumb, mix-up a super-small batch of CASTABLE REFRACTORY and press / smear that mix into the hole. If you have leftover CASTABLE REFRACTORY and want to fill some other holes - try to stick to the bigger holes (if there are any).