NateHMirage

To the OP a 18 inch forge is excessive relative to the work most people do. With a little creativity you could make a 14 inch piece with a 7 inch deep forge. Although you don't necessarily need to hear the entire cylinder it should be a length reachable by tongs and comfortably. You don't wanna reach a foot in lol. Once you add a hard refractory your diameter could go down half an inch. My all use forge has a five inch diameter and works for all my knifesmithing needs. 

To all the guys referencing sodium silicate I would advise against it. I used it in my forge and at high temps it melts and eventually the refractory sags due to how soft it becomes at heat. Colloidal or fumed silica is a better higher temp glue or rigidizer to use in your forge. It's a better investment. I use a hard firebrick floor to add thermal mass to the forge because the only issue with kaowool is in fact is insulating property. It's so good it cannot hold heat. Some thermal mass translates to increased heat time but less temp drop between heats in the forge. Happy forging gentlemen.

Frosty, the kiln wash i bought was a high zirconia mix which i further enriched with zircopax as a reradiating process. The wash was from the ceramic shop or store i think. Its a website titled that.

On 11/21/2018 at 1:34 PM, HojPoj said:

Sodium silicate is a completely different thing than colloidal/fumed silica.  While it does rigidize the fibers, it does so through  curing (like a glue, just requires CO2)... and at high temperatures can break down or act as a flux (eating away at your fibers).  Fumed silica rigidizes the fibers by vitrifying the microscopic silica and causing it to bind the fibers together (like brazing). That's why the recommended procedure is to apply rigidizer and fire each layer as they're applied.

What is the likelihood it eats at your fibers? I just applied it

No, do not buy your son that product. I am a sophomore in hs and have been forging for 2 years. A coal forge is simple to build as a father son project and will let him see if he enjoys it. A little future proofing in case your stuck with that forge. The forge itself is unsafe due to the uncovered blanket and the one layer of wool brings into question its efficiency.

Do not buy commercial rigidizer. Sodium silicate works and is sold in a gallon for 30 bucks by rutlands. Instead of itc 100 make the mix i posted about which is high zirconia kiln wash kaolin and zircon flour. I just coated my forge today and its fantastic. Tip for rigidizer is to put it into a spray bottle and add food coloring. That way it tells ya where ya sprayed.

In the search for itc 100 replacements(price) I had learned the original formula was near 70 percent zircopax and 30 percent kaolin. When shopping i came across a high zirconia kiln wash from "The Ceramic Shop" and went to thinking. It has already been tested and formulated and its cheaper per pound.... So i bought a box and some zircopax and kaolin.  My recipe was one cup wash, a third cup zircopax and one sixth cup kaolin. The mixture dried rock hard and seems to be very durable.