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Restoration Question: Lining Hearth Pan with Clay


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Hi all, 

   I've got a Buffalo rivet forge that's the brink of death; the blower is a little champ but the hearth pan is another story. If I don't do something to line the pan is gonna be a goner for sure. I found a picture of a forge almost identical to my own on ebay. (see picture) When I asked the seller how he went about lining the pan he reported to using tile mortar; which seemed dubious to me. So I delved into the iforge forums and found two promising posts. The fist, complements of Charles R. Stevens: 

He suggested "...buy powderd clay, (fire clay) and mix it with sand use the waterglass to wet it, then case it (place it in a coverd container and let the moisture even out) if it's to wet leave the lid off till its the right consistancy..." I replied to his comment, but I'm new to posting on here, I'm not sure if it went through. Charles, if you see this, how much of each of these ingredients do you estimate I would need? And what consistency should the mix be for application? It is like pancake batter, putty or play-dough? Does any one else have suggestions on this? 

Another promising recipe from HWooldridge was posted a couple of years ago.  

He says:

  •  "I recently lined a Buffalo forge that has the lips an inch or so above the iron hearth and it turned out well. The process is based on something I learned years ago when I used to help my grandpa build houses. In addition to carpentry, he did some rock work and one thing we would do occasionally is reline fireplaces. On horizontal areas, he would make up a mix, apply it dry and level, then spray water on top. This would rock up in a day or so without cracking. The mix I used (based on his recipe) was 3 parts mortar, 3 parts clean sand, 1 part fireclay and 1 part dry lime. I mixed it, poured in the hearth to a depth that was flush to the top of the firepot and raked it smooth, then sprayed only enough water on it until the surface was wet. I let sit two days before making a fire and it had hardened nicely with no visible cracks anywhere. I think the minimal amount of water helps eliminate the cracking."

I'm assuming he is referring to wetted mortar? But what type would be preferable? Any suggestions on this? I'm kind of lost... 

I apologize for posting a new topic on a subject that's been posted before; but while scouring these forums, I feel like I'm getting lost in all of the content. Please help!

Here is a photo of the restored forge with a tile mortar lining:


Thanks you guys, you all are always my first stop when I have a Blacksmithing question or problem to solve. 




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Typically, with natural or bought clay or Adobe mixes you chit for something stiffer than playdough. Say modeling clay or pasta dough

Lining a forge has advantages and disadvantages, mostly you must keep it under cover as coal and charcoal ash and water are costic and will find their way down between the liner and the pan if your forge lives out in the rain. 

Can you post a picture of the condition of your forge pan?

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Indeed, I focused on ceramics for a few semesters in art school a few years back, so I'm familiar with clays. But I've never worked with clay in this fashion, so I'm in the dark.

I wish I could post a picture of the pans condition, but it's currently in storage, so I can't access it right away. However, I did text my friend who owns the shop where it's kept, and he will hopefully send along a picture shortly. In the mean time, I found a few photos of forges in similar condition with the same type of build. One photo from another forum post: 

Pancho07 posted this picture:


And here's another from a google search:


Really my forge is about as rusted out as these pans; the fairly thin walls make me worry about issues with heat. On my pan, there is considerable rust damage where ash grate has been bolted to the pan. I was planning on reinforcing it with some plate. Something like the picture below, but instead of drilling holes, I was thinking I'd use a torch to cut a hole for a Tuyere to sit in. I found a pretty affordable one available by Centaur Forge.  



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Is it a cast iron pan that has "Clay Before Using" cast proud in it? If it's a sheet metal pan don't bother claying or worrying about losing the old one. They were made to be replaced and not necessarily with one bought from the company. Of course they'd really prefer you bought one of theirs but they were realistic enough to know blacksmiths tend to be . . . frugal and were a lot more likely to just replace it with what was at hand. 55gl. drum ends just so happen to be almost perfect.

If you want to clay it anyway, just dig some garden clay or out of a river bank, ditch, etc. It only needs enough fines to clump when squeezed if damp. 2-3 pts sand to 1pt clay and JUST enough water for it to clump if squeezed hard. If it won't add a LITTLE water and let it temper overnight in a sealed container. If it leaves mud or even damp streaks on your hand add some sand and let it temper. You know how mix clay yes?

Once you have it tempered ram it in the forge pan with a wooden mallet till the mallet bounces, scrape smooth and burnish makes for nice but it's not necessary.

Old timers often just tossed some sand in the forge or patted down local dirt with a shovel. All claying is for is to prevent spot heating around the air grate in a cast iron pan. Cast iron doesn't like spot heating it's brittle and the COE can cause problems, especially if someone bangs it when it's stressed.

Frosty The Lucky.

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Thanks Frosty! No, it doesn't have any sort of marking that I can tell. And it's so light weight that I'm not surprised that it's meant to be replaced. I'm really just avoiding replacing the pan for sentiments sake, as I inherited it from my grandfather. Kinda like Theseus' paradox, of the Grandfather's ax which has had the head and handle replaced. Anyways, functionally, I know it's a silly argument, but I'd rather at least try to keep the pan alive for as long as possible.

I'm on board with your clay and sand idea, what do you mean by burnish? I've only come across that term in leather crafting?

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So keep the pan as a wall hanger, maybe as a frame for projects you make. Get a plastic tub or wading pool it will fit in, put just enough water in it to cover the pan completely then dump in a couple three bottles of Naval Jelly, stir and let the pan soak. When the rust has reduced back into steel rinse it thoroughly neutralize the phosphoric acid with baking soda, rinse again and the instant it's dry oil or spray with pledge furniture polish to keep it from rusting. It WILL begin rusting immediately when it dries. If you let Naval Jelly dry on it without rinsing and neutralizing it will make a flat black phosphoric oxide patina that will resist rust for a good while. Might be worth just brushing Naval Jelly on it or buy a can of Ospho.

No it's NOT magic it won't patch holes rusted through it and won't replace lost metal but it will do a good job of saving what's there.

Just out of curiosity where in Mi are you? I married a UPer who lived in Ironwood at the time she received a particularly entertaining email I sent off to some friends. Long story but significant to me so I find myself asking.

Frosty The Lucky.

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We are talking more about Adobe and Ramed earth construction than ceramics. Tho with rich clay mixes an 1/8-1/4" will vitrify right around the ducks nest. 

Some folks have resorted to thinning stove cement and using perlite as agragate to form a lightweight lining, then coating it with strait stove cement for durability, others have cut and shaped hard fire brick ect. Many ways to skin this cat. 

Bank clay is strait forward (better than 50% clay) Adobe (30% clay) and Ramed earth (10% clay) are cheap and easy just dig up the local sub soil. 

Our English friends use ash and clinker and reform the fire hole as needed.

some folks use ash with clay and sand (ash, like lime or cement react with clay to prevent it from swelling when wet, their buy stabilizing it) 

lit isn't rocket science, just make mud pies ;-) 

a 2" thickness of earth will protect wood, 1" is good for steel. Myself I would fill the pan to with in 1" of the top, wile forming a bowl about 8" wide around the tuyere (plate in the bottom) possibly with a rim up to pan hight. This gives you an inch to place extra fuel on the table (coal) wile giving you a nice working fire. Not easy to get welding heat with out a couple of bricks to make it deeper tho.

lining the pan makes it hard to transport, many others resort to a steel bucket full of sand. Set up the forge, pore in the sand, wet it a little and form a fire bowl, use. Break down and let cool, pore sand back in the bucket and pack up...


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Frosty, I am definitely keeping that Naval Jelly trick up my sleeve for future use. Either way, I'm still on the fence. I would like to do a new forge build, especially if it's an eventuality anyways. The only issue is finding the material and the time. During the summer season when I'm teaching classes day in and day out, so I don't have a ton of time to put aside for scouting out the right drum, planning the build..I have a bad habit of being too meticulous about my projects, so they take way longer than they should. Anyways, yeah, I'm in west Michigan, definitely not as cool as the UP though.

Charles, thank you for your suggestions, I feel a lot less in the dark now. I think I come across more 'ways to skin a cat' on these forums than any other, Blacksmiths do have a knack for that though.

But, anyways, I'm already looking into adobe clay and it seems really promising -and affordable! I'd plan on digging some up, but I don't live in a clay-rich area, there's just sand, lots and lots of dusty sand.

Thank you both for your helpfulness. I really appreciate it. :)

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26 minutes ago, clinkertinker said:

...this is true. Do you have to grind it up or pulverize it or anything? I watched someone destroy a coffee grinder on youtube the other day for just that purpose. Seemed like there had to be a better way.


Just wet it and let it stand overnight, BTW, kitty litter, it's cheap and one of the few products blacksmiths worldwide don't try to recycle!:D

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I want to meet whoever was the first one to be like walking scooping kitty litter and then thinking, "ya know what, this'll do just the trick!"

How does it stand up in the heat..? Do clinkers like to cling to it? I have absolutely no idea basis of knowledge about kitty litter, haha ours are all outdoor beasts.    

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Clay kitty litter is Bentonite clay, you don't have to be particularly insightful nor inventive to use it for forge liner. Ever watch casters plug the tap on a cupola melter with a glob of mud on a long handled rammer? Ayup bentonite, takes molten iron without noticing, heck I don't think it even vitrifies at that temp range, 2,700f - 3,000f typically.

For a forge pan rammable recipe, wet the sand before mixing in the kitty litter, 2-3 pts. sand to 1 pt. clay and let it temper in a sealed container for at least a day. No you don't need to crush it but if you want to why not. I'd use a mortar and pestle arrangement though, coffee grinders and blenders tend to suffer the experience. Bentonite just takes a goodly temper time but a day is usually plenty.

Just don't wet it like you were going to throw it, just moist enough to clump if squeezed hard is perfect. If you mix it like throwing mud it'll shrink check as it dries envision dry mud puddle. 2-3 : 1 sand gives it porosity so it dries evenly through out and lends it some flexibility so it minimizes shrinkage. It also makes it more resistant to thermal cycling. Adding grog won't hurt just make it sand fine.

Frosty The Lucky.

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