How to Clay a Forge

[FTB2]

Just gettin' started in this and havin' a great time. tryin' to get my "shop" together. I have recently purchased an old forge and blower. I have done some research (which is very cool) and found info on the blower - Otto Canedy Western Chief, but not on the forge. All I can tell is that it has - "Clay foge before using". I have purchased some fireclay. My question is - how thick to apply the clay? what about around the fire pot ? What else am I not askin'?

Having fun bringing these old tools to life again.

Thank you in advance and God bless all of you

Merry Christmas and Happy New year,

Mike
Buckeye Lake area
Ohio

Go Bucks!

[Frosty]

Welcome aboard Mike.

Only use enough water to make the clay clump in your hand when squeezed hard. If it crumbles add a LITTLE more if it's sticky add some more clay or let it dry. Adding about 1 pt in 3 of sharp silica sand will help as well as will adding grog. (crushed fire brick)

When you have the right moisture ram the clay in about 3/4" thick and about 1" near the air grate. A wooden mallet is perfect but the end of a 2x4 or 4x4 is fine. You want to ram it as hard as reasonably possible, the mallet will begin to bounce.

Once it's rammed in use a sharpish object and scrape it smooth, the end of a 2x4 or a wooden spatula works well. For the final finish burnish it with a piece of burlap wrapped around a wood block.

The last thing to do is score it with a butter knife, etc. This is to provide expansion joints or more properly shrinkage joints. The clay will shrink check as it dries and crack like a lake bottom if not scored. The score marks will make it crack along them in a controlled manner. I usually do pie wedges and one or two cross scores, looks kind of like a stylized spider web.

Now you want to let it dry thoroughly before you fire it. If you have high humidity or cold temps you may need to hang a light bulb over it. Once it's dry build a wood fire in it with kindling a couple inches deep, let it burn itself out and cool, then repeat with a deeper stack of wood 4-6".

All this seems like a lot of work seeing as you can simply dig some clay out of a river bank smooth it in and go to work but doing it that way tends to make a temporary liner. This is actually preferable if you're going to use it for a mobile set up.

Anyway, ramming it damp, smoothing, burnishing, scoring, drying and firing will make for a much more durable liner that won't gouge easily and clinker won't stick to as easily.

Frosty

[Nelson44]

hello i to am haveing trouble with claying and makeing a refractory for my forge. Sounds like you have a coal forge. I am useing a gas forge and the mix i put together has melted it is goo at forge temp it took quite a while to get to the goo point. So any ways i am looking for a good refractory mix too what i used last time was 20 to 25lbs of fire clay and 25 lbs of morter mix and One small bag of vermiculite and proubly too much H2O. i am going to try something diffrent i think i still got 30lbs of fire caly left.

[Frosty]

Perlite has a melting temp of 2,000f and vermiculite is lower than that so that's what's gooing your forge liner.

making your own refractory for a gasser isn't usually very successful, I don't know of anyone who'd done it. Your best bet is to contact a furnace supplier or search out a company online that will sell you a castable or rammable refractory. Still, even the factory refractories melting temp goes down as it's insulating quality goes up. Unless you have the $ to buy bubble alumina.

Another option is to make a thin 3/4" or so hard inner liner and wrap it with ceramic wool refractory for insulation. My old pipe forge is a dual lined forge and it's served me very well since 95 or so.

Lots of available options.

Frosty

[richmond1905]

Hi I am working with a 1902 coal burning forge, and I wanted to replace the clay in it. The old clay which was in it until alittle while ago had cracked, and was pulled out by my master. I was reading on other blacksmith sites that since I work outdoors with the forge, it may not be necessarily be a good idea to line the forge with clay. Unfortunately though, there seems to be some thinning of the metal in the fire pot (via rusting, etc . . .), and I am wanting to do what is best for the forge. Any advise including how and if i should install the clay would be greatly appreciated.

[Rob Browne]

Richmond,

Welcome to IFI.

For the how to line your forge, read Frosty's first response in this thread and you won't go wrong.

Between uses, I take it that the forge is stored indoors and out of the weather to reduce rusting?

Cheers

[richmond1905]

Thanks Rob for the advice. As to your question, the forge is only stored indoors during the winter season since it gets used 5-6 days out of the week. To reduce rusting, it is kept under a fire retardant canvas tent, and covered by multiple tarps.

[Shainarue]

Resurrecting a really old thread to ask a question about Frosty's first response in regards to lining the forge with clay.

The original poster specified they were using "fire clay". Is the response specific to fire clay or is it the same advice if using clay from the ground? 

[anvil]

Fire clay is different from clay in the ground. Check out castable refractory.

[Frosty]

You can use fire clay or clayey soil from where ever but reverse the sand/grog clay ratio to 1 pt. clay to 2-3 pts sand/grog. Only add enough moisture it will ram hard. Do NOT make mud or it WILL shrink check as it dries.

The sand/grog allows moisture to escape when you build a fire and provides room  for shrinkage and minimizes shrink checking. Fire brick or old pottery grog won't make glass at high temps and works better in a forge clay liner. Another thing I've changed my mind about is when you can put it to work. Ignore the lengthy dry and cure advice above, if you don't make it too wet you can put it right to work. 

Castable refractory in a coal forge traps water  against the pan and promotes rusting. 

Covering it when not in use is a good idea, I like a steel trash can lid once the fire is out. 

Frosty The Lucky.

[Shainarue]

Thanks for the quick response! Hopefully I can get that worked on this week so it's ready to go when the blower is finished.

Question about grog: can it be wood ash like was recommended when I made the JABOD? Of if not ash, then does terra cotta count as pottery? Or old coffee mugs? 

[Frosty]

Not wood ash, it acts like cement and you want grains to let steam escape and provide movement so expansion / contraction of thermal cycling doesn't damage the clay. Terra cotta should work but I can't say for sure. Give it a try and let us know please. 

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Terracotta will work, just smash it up pretty fine. I'm going to experiment using some left over Raku clay with sand mixed in on a charcoal side blast forge I'm building.