Re: Refractory blanket how-to for welding forges.
Please check your email, as I emailed to you my email address so that you may contact me directly, and that you may let me know where to mail a copy of my book.
True, time and knowledge marches on. The instructor of the first welding course is a great and generous guy, and nowadays just about every seasoned smith in the guild now knows how to forge-weld.
I may be mistaken, but the general consensus about gas tubes for knife forging seems so far to be a five to six inch diameter tube about twelve inches long. Also apparently the further one gets from a round tube, the more likely people are saying that it will have hot and not-so-hot spots. The NC brand Wisper Momma forge that I have been using for about 26 years definitely has only two hot spots. I can see the benefits of having a specialized forge for each specialized application, especially a highly insulated forge with a protective surface to reduce costs of fuel and damage to the forge.
It is difficult for me to visualize the use of ceramic saggers, especially when the goal would be a round 6-inch tube, 12-inches long. Are you suggesting that I cast curved pieces from catable that can be assembled into a tube?
As for two gallon can versus five gallon can, yes a gentleman was at the last blacksmith convention that I attended using a disposable refrigerant tank. I purchased a burner and his plans for his setup from him. On one hand the options described by various folks tends to be daunting, but on the other hand there seems to be a lot of shared features and overlap.
I attended a presentation last winter where the construction of an adjustable size forge and burners were demonstrated. He used rigidizer, a layer of castable and ITC-100.
It would seem that a 12" diameter container with 2" to 3" of ceramic wool, a 1/2" coating of castable, and a reflective inner coating would result in a 6" tube. So far this seems to be the common description of building a specialized knife forge from various sources. I lean towards 3" of wool for such a forge in the hopes of reducing heat loss.
If I cast a tube that is 6 inches ID, with two-inch walls in the casting, would surrounding that casting with insulation reduce heat loss?
I do have a copy of your book in front of me.
Again, please check your email and forward a snail-mail address to my email address so I may send you a copy of my book.
Recently someone on one of the casting groups commented that there was no such thing as a cement that can have all of the water baked out of it; I believe this was done in defense of the use of Portland cement in a homemade castable refractory. The official answer would be that the chemically locked portion of water in lime based cement cannot be baked out, but the chemically locked portion of water in refractory cements can be. I have always accepted this official version as the only reality...in the past. The limiting factors on "baking out all the water" are that the refractory must be taken to yellow heat in the first place, and that over time, water content can recollect in refractory if you're not careful to seal the refractory surfaces against water vapor in ambient air.
However, truth of any kind is seldom found effortlessly; including technical "truths". I suspect that a healthy debate, with both sides airing their views, might adjust what the majority of us accept as practical reality--to our mutual profit; this could be important for people wanting to make insulating refractories as secondary layers. Homemade refractory as an insulating secondary layer might be quite forgiving of official standards; standards useful for hot-face layers may constitute a waste of money in secondary refractory layers.
While casually dismissing the Portland cement idea, I have noted both resentment, and a strong hint of "I'll match your official facts with personal experience" in passing (heated) comments from the other side of this issue. Isn't it time they had a FAIR hearing; something open minded, maybe?