kenG Posted October 11, 2008 Share Posted October 11, 2008 This is just the first of what I'm sure will be hundreds of beginner questions. I appreciate the warm welcome and the willingness to help. This is the little portable forge I picked up. It has "clay before using" cast into the metal. I hope I'm interpreting what I have read in the archives correctly and it is ok to use without the clay linner. What are the reasons for linning with clay and what will it hurt to not line it? Quote Link to comment Share on other sites More sharing options...
MLMartin Posted October 11, 2008 Share Posted October 11, 2008 the clay acts as a buffer between the metal and the coal fire, the fire will be so hot that it will heat up the cast iron firepot quick and its vary likely to crack and break. ive seen many people just use old red clay right out of the ground or any other clay they can get there hands on, im sure there are better clays ment for this, but i dont know them, and ive seen the pot covered with clay about as thick and half and inch up to about one inch. just line the firepot, or the bowl that the fire sits in, let the stuff dry for a day or two, then start a pretty small fire, and let it burn for a little bit to dry out the clay. if ya dry it out to fast it will crack off, but its just clay so no worrys this is just what i have herd and exsperanced, im no expert, just my thoughts on the matter good luck and happy forging Quote Link to comment Share on other sites More sharing options...
hill.josh Posted October 11, 2008 Share Posted October 11, 2008 the clay is like an insulator and it protects the iron from burning up and then needing to replace it, ive used clay from a river, mud from my back yard, and then a mixture of portland cement and sand where it was 3 parts sand to one part portland cement and some water(enough to make it feel like fairly wet mud). the last of the 3 is defiantly the strongest against knocks. the mud eventually falls apart but is easily replaced and is free. ive heard that portland cement will spall but its never happened to me and is what i use right now.. not saying it won't spall but just that it hasn't happened to me. don't go on what i say though just cause i said it.. do what you think is safest. Quote Link to comment Share on other sites More sharing options...
hill.josh Posted October 11, 2008 Share Posted October 11, 2008 my firepot is actually made completly of portland cement/sand so I don't know what would happen to an iron firepot if it would crack or not.. i haven't heard of that i just know that iron will burn up. Quote Link to comment Share on other sites More sharing options...
kenG Posted October 11, 2008 Author Share Posted October 11, 2008 Josh, When you say Portland Cement, I assume you are talking about type I Quikrete like Ace sells? and just plain ol' sandbox sand mixed together? That's simple enough. Thanks, Ken Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted October 11, 2008 Share Posted October 11, 2008 i have used forges with out lineing them ... if you heat them up quick you can cause the cast iron to crack .. its a expantion thing i think . anyway clay the bottom but leav it thinner towards the grate and expect clinkers to stick to it occationally. Quote Link to comment Share on other sites More sharing options...
Meisenmann Posted October 11, 2008 Share Posted October 11, 2008 An additional bonus if you clay your forge: Better Insulation and less coal usage, therefore saved money. Build a small roof from "autoclaved aerated concrete", very cheap stuff but it works. Therefore even better heat retention and you can better judge the colour of the steel. Quote Link to comment Share on other sites More sharing options...
philip in china Posted October 11, 2008 Share Posted October 11, 2008 Mix some coarse sawdust (chainsaw dust is best) with ordinary clay out of the ground. The sawdust burns as soon as you light the fire. This gives little air pockets which greatly increases the insulation value of the clay. The local smith here just picks up clay from the ground. He is 81 and has been smithing since his teens so probably knows something! Quote Link to comment Share on other sites More sharing options...
jimbob Posted October 12, 2008 Share Posted October 12, 2008 (edited) I believe the clay acks as a buffer from coal as a lot smithing coal has sulfur in it and when you add water to to coke it the sulfuric acid leaches out and will rot the cast Iron pot/bottom/firebox out. Its myunderstanding that cast iron resist corosion better than steel...whence one of the reasons for the cast iron forge as apposed to steel Edited October 12, 2008 by jimbob Quote Link to comment Share on other sites More sharing options...
Rob Browne Posted October 12, 2008 Share Posted October 12, 2008 I just line mine with a mortar mixture like used by brick layers to fix bricks into position. Simple, cheap and if it breaks then easily fixed/replaced. Quote Link to comment Share on other sites More sharing options...
Warrigal Posted October 12, 2008 Share Posted October 12, 2008 By trolling the web I got the suggestion of lining the bottom of my "forge" with ash and dirt ( ash from my wood fired heater) Forge is in inverted comma's because it started life as a comercial charcoal fired BBQ I plan ( tomorrow if the stars are in alignment or whatever it is that delivers other jobs for me to do) to "strain" all the charcoal out of the Firebed and then cover this insulating layer with a layer of clay I got from my sister who works in an Art supply shop. As it turns out mum and dad have just dug up their back yard and removed a lot of clay, that will be finding it's way over to my place somewhere in the next week. Outta interest my cast iron fire, closed in like a modern combustion stove but externally all cast iron. Has burn only wood cast into the front wall. Pity lotsa coal around here. Carl Quote Link to comment Share on other sites More sharing options...
kenG Posted October 12, 2008 Author Share Posted October 12, 2008 I getting the impression the linning material isn't has important as just having a buffer material. Thanks for all the responses. Ken Quote Link to comment Share on other sites More sharing options...
hill.josh Posted October 12, 2008 Share Posted October 12, 2008 Josh, When you say Portland Cement, I assume you are talking about type I Quikrete like Ace sells? and just plain ol' sandbox sand mixed together? That's simple enough. Thanks, Ken Ken, its type I/II quickrete so I think its the same. Just as long as its portland cement and plain sandbox sand is what I use.. good luck forging man Quote Link to comment Share on other sites More sharing options...
civilwarblacksmith Posted October 12, 2008 Share Posted October 12, 2008 One question would be, How thick are the walls and floor of your forge. If the are 1/4 thick or thicker and you are not a professional full time smith that will be operating the forge 8-10 hrs a day everyday, you really don't need to line the forge with anything. I have 2 forges that are at the least 1/4'' and have no lining material. One is used about everyweekend for re-enactments. I just picked up a used forge and fixed it up for use on the following weekend. When bought, this forge had a refractory material in it. I believe it was cement. The sides are 14 - 12 guage and after breaking the material off the bottom I found it to be about 14 guage (heavy 1/16") metal. That was why they lined it. I have since replaced the bottom with 1/4" plate and do not need lining. Quote Link to comment Share on other sites More sharing options...
azIRonSmith Posted October 13, 2008 Share Posted October 13, 2008 Definitely clay the pot. It's a lot cheaper to replace clay than it is to repair/replace the pot. I would stay away from cement. It tends to spall at high heat (i.e. explode). A better clay would be a cone 10 (ceramics term for high fired) clay from a ceramics supply store. You can get 25lbs bags for about $6-$10. I add some very dry sand and I also use vermiculite as a filler similar to the sawdust that philip suggested. Since this clay is meant to be fired at over 2000 degrees, it will stand up to the heat of your forge. Ground clay may contain anything and everything and you have no guarantee as to the heat rating. It may literally melt in your forge. You will want to let the clay air dry for quite a few days depending on your weather. Dry and hot = less days. Cold and wet = more days. This is to let the clay mix dry out slowly to keep it from cracking. Keep some extra clay mix in an air tight container to repair any cracks. Once you are ready to fire it up, do a small fire or even wood fire to allow the rest of the moisture to slowly dry out the rest of the moisture. This will help keep the clay from cracking a lot on the first fire. There is being frugal and then there is being down right crazy dangerous cheap. ;-P Quote Link to comment Share on other sites More sharing options...
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