This may not be the fastest forge to build, but it was worth the time. These ingredients have been used on all my clayed forges. The secret is slowly curing and really rehydrating the kitty litter before hand:
A dirt cheap recipe for fire hardening clay in forges— Works great for projects big or small; I just winged it loosely off of some other recipes. This is an approximation. That was modified as I went along and needed more. I just went for something that “looked right”.. not that I knew what that was. I started off drier and got wetter to keep the large mass from cracking:
-1 20lb Bag kitty litter (the unscented bentonite clay kind) is barely covered with water in a wheel barrel.
-Add three full shovels of sifted red ground clay. (Sifting is really just a formality, but it should be done dry.. if it’s from a deep enough hole.. like a charcoal barrel pit then it’ll be well clumped and moist almost pure clay)
-Stir it all together and wait at least 24 hours. Occasionally stir to make yourself feel productive. =P This will soften the clay pellets as they absorb the water. Additional stirring will make sure all the mix stays wet. (The weather was mild, but cool at night when I did this so use less water in winter, and possibly more in summer)
– Once about half the standing water is soaked up or evaporated. Then add about equal parts wood ash and kitty litter to the mix until it’s to the desired consistency. For a single layer about an inch that’s something that clumps together in your hand without crumbling.
This mixture should to cure very slowly.
I would apply it in about one inch thick layers around firebricks letting them dry 24-48+ hours in between. I used a heater and halogen light at night because it was getting into the high low 60’s. I’d check on each layer to keep the outermost “skin” moist. The goal was to avoid lots of steam from the inside escaping and cracking a dry outside. After many layers were applied I waited maybe just over a week with 75-degree heat and air movement. Then I built a small wood fire in my new forge. I built it up to a nice sized fire taking up the whole forge over a few hours and then let it burn HOT for half an hour before letting it slowly cool.
This forge wasn’t a single afternoon project, but it’s served me for a long time now:
A tip with all clayed forges used with coal is to leave a thin layer of ash in the forge, or even apply a layer mixed with very little water. This will help prevent clinker from bonding with the clay. Instead it bonds with the ash.
I’ve found this sort of fire useful to heat several inches of steel. In this particular fire I forge welded a small hook out of 6 inches of half-inch square. Then finished working out the edge of a knife with a seven-inch blade.
I use many different types of fires and I am by no means an expert. Working odd bends and unusual shape or sizes without destroying a coal fire is difficult for me. It’s easier when extra coked coal is on hand, but coke still has to be raked back or added. Time must be spent waiting for the fire to get back up to temperature once burning coke is displaced. Proper fire management is one of the most basic skills anyone wanting to learn blacksmithing should know. I’ve had to teach myself most of these skills but I’ve by no means done it without the advice of others. I’ve not seen a good step-by-step pictorial on the subject so hopefully some may find this helpful. I plan to post a similar post over at Iforgeiron.com. It has been asked about an awful lot lately and I know many people like me are unable to attend classes. Around here, even at the events I’ve been able to attend, gas forges have been prominent or coal fires were started early and maintained irregularly and without discussion.
This is my side-blast solid fuel forge.
shopvac, or any other air source.
(optional) 3/4″ PVC, ball valve and preferably on a T-fitting.
1 inch steel pipe
clay slurry (clay, water and woodash)
Fired clay bricks. (Not cement blocks)