mixing Fire Clay

[Narrow Path]

My name is Joe Marsh (AKA-Narrow Path, Florence, SC) I am relatively new to the heating and beating scene. Last fall I got my first forge, a Champion blower with a cast iron bowl approx. 24" dia. I was advised by a friend to line the base of the bowl with fire clay in order to build up the bottom to the level of the tuyere. This will also provide protection for the bowl. I came across a bag of medium duty fire clay (powder form) which is for temps of 1400F to 2200F. However, when the guy gave me the bag he said I should need to mix with silica sand / cement morter. My question is what kind of ratio I should use. Any ideas?

[Old N Rusty]

many years ago (14) i heard Frank Turley recommend a sand/ cement mix 3 parts sand -one part cement .(portland cement not concrete) mix it moist and it will mold well it has worked in my demo forge . that works. i dont know anything about fireclay, pax

[Narrow Path]

many years ago (14) i heard Frank Turley recommend a sand/ cement mix 3 parts sand -one part cement .(portland cement not concrete) mix it moist and it will mold well it has worked in my demo forge . that works. i dont know anything about fireclay, pax

I suppose all of the heat is above the clay so it must not matter if you use the fire clay.
Thanx for the reply

[Frank Turley]

Sorry I can't help too much here. If the fire clay is mixed with water and applied, it will shrink and crack. By hearsay, I was informed that you could temper the fire clay by mixing it with fines and fly ash from the forge, and that would help prevent the cracking. In any event, the dang clay is brittle and you have to be careful you don't break it with your fire rake or shovel. Some of the old, round rivet forges had a pressed steel hearth and sometimes they were stamped, "Clay before using." Hardly anybody does that anymore, and most of those forges had a flat, central tuyere level with the hearth. Probably, the reason for suggesting protecting the hearth is to save it from getting too hot when rivets were being heated at a building site all day long...especially if it was pressed steel. Nowadays, they nut 'n' bolt the structures together.

As Old N Rusty suggested, I line my large rectangular hearths with a cement/sand mix to the level that the firepot flange protrudes above the hearth. I learned that method in horseshoeing school in 1964. The interior of the firepot is hot, but the hearth doesn't get that hot, so it doesn't need a super duper refractory.

I suppose if a guy needed a reasonably good refractory, he could use the pre-mixed "pasty" Furnace Cement available from any building supply.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[thingmaker3]

Clay, including fireclay, is best used as a binder rather than a structure. Clay is used to hold the structure together. Use only enough clay to get the structure to hold together. Use as little water as possible as both shrinking & cracking are caused by size change during drying.

[Rob Browne]

I simply use the ready made brick mortar from a hardware. Mix it, mould it to shape and leave for a week or two then stick a wood fire in it, let cool then off you go. I have had to touch it up a bit after about a year and a half.

[OddDuck]

If you have the fireclay, use it. Works fine, mix it 2 or 3 to 1 sand/clay. Moisten with only enough water to make it like crumbly cookie dough, put it in a plastic garbage bag for a day or two to even out the water content. layer it in to your firepot, and ram it down with a short section of 2x4 to make sure there are no voids. Either let it dry on its own for a week or so, or just build a fire in it to dry it quick. Nice thing about the clay liner, all you have to do to repair it is moisten it and spackle the cracks closed. Easy peasy.

[zach124816]

what shape do i want to end with? my forge is 18 inches across and 5 inches deep flat on the bottom.

[SmoothBore]

Well, ... I'm just guessing, ... but I suspect the practice of "claying" dates back to a time well before commercial "fire clay" or "refractory cement" became available.

Clay, ... on the other hand, ... was universally available, ... for free. :)

Be it clay, ... or Portland cement, ... or plain old sand and ash, ... I'm sure that using "something" to protect the bottom of the forge pot, ... is better than "nothing".


As for shape, ... the traditional "Ducks Nest" has served pretty well, for a couple hundred years.


.

[Francis Trez Cole]

here is a good link http://www.backyardmetalcasting.com/refractories.html

[Backwoods Blacksmith]

When I made the fire pot for my rivit forge I made a form for the ducks nest from a piece of 4x4 lumber 6 in long. I filed a 1/2 in taper on all four sides and centered it over the blast. I wrapped the wood in a plastic bag to keep the fire clay from sticking. Mixed the clay 3 to 1 with clean sand and enough water for the mix to stick. Pre mix the dry first. Pile up the wet mix around the form, tamping it down as you go, up to the top of the form. Then either taper the clay down away from the form to the pan or if you have made enough make it level, tamping it all firmly to help displace air pockets and excess water. Once all the tamping was done I removed the form and radiused the edges. Allow to dry in a cool dry area for at least 3 days, depending on the weather, At this time of year 5 days. You could cover with a box and warm it with a light bulb if it is cold and wet. The trick is to drive out the moisture SLOWELY. After drying light a wood fire in the pot and keep it fired for a couple of hours. The idea is to build a bed of coal and just let it work. Charcoal will work. As it burns down keep adding fuel. This will cure the clay and harden it for years of service. I realize that ther are 100 different ways of doing this but this has worked for me several times with no problems. DO NOT GET IN A HURRY.
Good luck and have fun.

[Robert Yates]

Here is where I get mine .

http://www.vitcas.co...-cement-mortars

http://www.vitcas.co...ractory-mortars

http://www.vitcas.com/ceramic-fibre-products-5

Sam

[tomhw]

Sorry I can't help too much here. If the fire clay is mixed with water and applied, it will shrink and crack. By hearsay, I was informed that you could temper the fire clay by mixing it with fines and fly ash from the forge, and that would help prevent the cracking. In any event, the dang clay is brittle and you have to be careful you don't break it with your fire rake or shovel. Some of the old, round rivet forges had a pressed steel hearth and sometimes they were stamped, "Clay before using." Hardly anybody does that anymore, and most of those forges had a flat, central tuyere level with the hearth. Probably, the reason for suggesting protecting the hearth is to save it from getting too hot when rivets were being heated at a building site all day long...especially if it was pressed steel. Nowadays, they nut 'n' bolt the structures together.

As Old N Rusty suggested, I line my large rectangular hearths with a cement/sand mix to the level that the firepot flange protrudes above the hearth. I learned that method in horseshoeing school in 1964. The interior of the firepot is hot, but the hearth doesn't get that hot, so it doesn't need a super duper refractory.

I suppose if a guy needed a reasonably good refractory, he could use the pre-mixed "pasty" Furnace Cement available from any building supply.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

My forge is reinforced concrete. The cast iron firepit is expendable. I plan to replace it in ten to fifteen years. I will be 75 or 80 years old then. Where is the problem?