Jump to content
I Forge Iron

Stretching my refactory cement by mixing with other materials.

Recommended Posts


I'm building my first forge / smelter.

i have 19 firebricks and 10lbs of refactory cement.

id like to use coal/air for my heat.


Id like to build my forge in a square shape, using the firebricks stacked the skinny side, they are 2 inches thick if i remember right (the whole inside lined with a refactory mix). (firebrick for the bottom of the forge, with refactory mix) with one brick at the base missing. id put a pipe a little bit into the missing brick hole, and refactory in the inside to fit it, with a hairdryer duct taped at the other end. 

I have to work out the lid to the furnace, not sure what i should use...


for my refactory cement, i only have a 10lb tub. Id like to stretch it by adding things to it.


1) 10lbs refactory

2) crush up 2 or 3 firebricks and mix in...

3) i have a tube of Quikrete sand. i looked it up, and it said it was silica sand.

4) i also am thinking of crushing up clay cat litter 


Are there any of the 2-4 things that i should or shouldnt put in the mix?

and if i should use all four to stretch the 25$ refactory i bought, what ratio should i use?


Also is there a way to make a homemade crucible? or what stores readily carry them..

Also, how thick should the refactory mix be, on the inside of the firebrick..

Any suggestions on what kind of pipe i should use to bring in the hair dryer air?




-i read the hair dryer should be on low, not high so it doesnt force the heat out..

-how long should the refactory mix sit before its ready?

-if build it/insulate it, and put a mild heat source in, will this steam out the water from the mix and cure it, so it can handle forge temp?

-also, should i put any refactory between the bricks acting as a mortar?

Link to comment
Share on other sites

What are you planning to smelt and where are you getting the ore?  Or are you planning to build a foundry and melt metal?

If so (smelting != melting !!!!) may I commend to your attention backyardmetalcasting.com as a place more focused on your endevors...


I use a bloomery when I smelt iron from ore and prefer to use magnetite ores and be happy to discuss *that* with you.  "The Mastery and Uses of Fire in Antiquity", Rehder, has plans for a "foolproof" bloomery in an appendix.


I will not help you make homemade crucibles very much in the same way I will not help you make homemade drugs or explosives---the liability is too high and helping friends perfect their Freddy Krueger look is not something I'm into.

Link to comment
Share on other sites

Ok a foundry and not a smelter (which takes ore and reduces it into metal).  No harm, no foul and when you visit backyardmetalcasting.com you won't sound quite as clueless...


Do note that foundries (and smelters for that matter) do not generally make good forges and vice versa.

Link to comment
Share on other sites

Buy the crucibles, don't skimp. Much, much safer.

Refractory - Look at the backyardmetalcasting.com site, I've successfully used their refractory recipe for years, and made a few variations on it. It's definitely not industrial, but it'll serve up to brass/bronze. And get some fireclay from a masonry or contractor supply, it's not very expensive, and much cheaper/less messy than the cat litter route. In a fix, you can sometimes get sodium bentonite from a feed store. It's the powderized version of your cat litter, and is sold as a pond liner, depending on where you are in the country.

Hairdryer - will work, I'd reccomend running it through a pipe with some kind of airgate. Doesn't have to be complex, a slit on both sides of the pipe, and a thin flat bar with a hole cut out, that you can slide through the slit to provide varying amounts of air. (Also, too much air, too fast, and your metal will melt faster, but you'll also have a lot of issues with oxidation, thermal shock causing crucible failures, etc....)

Firebrick - works fine as grog. So does regular brick. Main thing is it has the moisture baked out.

Sources of info - Phil Gingery books, backyardmetalcasting.com, an experienced friend. (of these, I highly, highly recommend the last one, it'll save you a lot of mistakes, and make the overall experience a thousand times more rewarding and safer.)

Safety rant - short version today - Get an experienced friend. Don't skimp on crucibles. Stay away from zinc, galvanized metal, and brass until you've learned a lot more. - You do NOT want fume fever. Use PPE. Leather gloves, Leather apron, Eye protection (never ever ever leave this one off. Steam explosions and flying molten metal suck.) Long sleeves and pants with natural (non-melting and sticking to your skin) fibers, Good ventilation and depending on what you're casting, fans. Did I mention get an experienced friend?

Also, for homemade refractory - let it sit about a week or so, after it dries the first day or so, put a light bulb inside the furnace to help it along. Do NOT apply intense heat rapidly, as again, steam explosions and flying refractory chips also suck.

When it's been a week, build a SMALL fire inside of it and let it burn for an hour or so, preferably with the cover on, to drive out any moisture, and to see if any trapped air or water pockets will explode holes in your refractory walls. (always fun, might be patchable, might not.). See note on flying refractory chips above. Then, pre-heat, and bring the heat up to casting temps slowly the first time you use it.

Link to comment
Share on other sites

Welcome aboard Ian, glad to have you. If you put your general location in the header you might be surprised how many of the IFI gang live within visiting distance.


I'm having trouble thinking of any advice I can give you other than: Take a course in casting, read something other than blogs and view youtube videos for research. You just don't have enough knowledge to even attempt casting without serious risk. Seriously, you're at the casting fishing weights and bullets beginner stage and even then you're talking potentially crippling risks.


Ian buddy, I don't know you from Adam but I don't want you or someone close to you coming to harm. Casting any metal is extremely hazardous, even with the proper safety gear. You're choking over having to maybe buy another $25.00 bucket of refractory. If you added two more zeros to that cost it wouldn't be something to bother you if you have any business casting.


A couple  numbers to think about. 1 gallon of 212f water changes to 1,600 gallons of 212f steam. The higher the temperature at the phase shift the larger the volume increase. So, 10lbs. (about a coffee mug full) of 2,300f molten iron has the same energy stored in it as a CASE of 40% dynamite. Consider what's going to happen if a 50 lb. crucible (pretty small, one man pour) of molten iron spilled on damp soil or bare concrete, globs of MOLTEN 2,300f iron are going to be flying for yards in every direction. It's a welcome to hell scenario.


Frosty The Lucky.

Link to comment
Share on other sites

Thanks for the words of wisdom nobody special and frosty :)


I posted on http://backyardmetalcasting.com/ aka http://www.alloyavenue.com/vb/forumdisplay.php?13-Foundry-engineering-and-construction forum board.


what i posted there was the same as here, then this post after...



the refactory cement says Heat Stop II
blend of clays and high temp cements.
says its designed for firebrick.
says can be used for repairs in kilns, furnaces, etc..
'heat stop with a temp limit well above 2000

the bricks are whitish, a little brittle.. 
they are good sized, and 2 inches thick, so i was gonna stack em the skinny way and put the refactory on the inside..
should it also go on the outside? or imbetween the bricks as a mortar?

i have access to a metal trash can, if i need a structure outside the bricks it'll take some scrounging..
i have a small charcoal grill, which i was going to originaly use. If i made a mix for the lid would that work?

Also i have another regular size grill.. its propaine so i could either use that as the fuel, or rip that part out,
firebrick and insulate.. (For the Forge)

Or maybie i could make a foundry, for melting metals to cast them..
and.. a forge out of the propane grill for heating and working with metal.

any ideas/suggestions/comments?



I want to make my own alloys.. wiki has a list of them and percents of which metals.

1) I want to find a metal/alloy i can melt/mix, and pour into a shotgun slug mold suitable for shotshell reloading.. (not a lightweight metal. maybie a combo of a heavy and light metal in an alloy)
2) Also id like to make my own knives (and machetes), full tang, id use paracord to wrap the handle.
I dont know much about tempering a knife, (get it red hot, then quench it/repeat?)
so when i get that far a forge would be handy..
3) id like to experiment with making alloys.. and learn along the way.

Id like to learn more about Carbon. my understanding is to make steel you take 99% iron and mix with 1% carbon.
so i need to find out if carbon has other uses and how to use it, etc..


I found a medium size metal trash can in the barn (with lid) and brought it up. (for the foundry not forge.)
i thought
-line the bottom with silica sand, for weight and heat tolerance, 
then saw/file my firebrick to line it,and have it fit together.
then connect a hair dryer to a pipe that inserts into a hole just above the sand, for forced air. (gap in insulating liner)
in my first post i asked about a 4 part refactory mix .. heat stop, clay (crushed cat litter), the sand, and ground firebrick.
so hopefully have enough mix to protect the bricks and fill gaps.
from filing the firebrick to fit in the can, i should have a lot of it as a powder, to add to the mix..
the bricks are square so there would be air pockets behind them. maybie a clay/sand mix?
with firebrick on the bottom to rest the crucible on.
and coal around it, fed by the forced air, hairdryer pipe.
was thinking some high temp hinges to connect the lid to the can, and put the mix on the inside part of the lid.

any opinions, critique, suggestions?




Edit:Metal Trash can Foundry design

1) about 1.5 feet of silica sand on the bottom (temp/weight)

1a) should i put something like firebrick powder/clay above the sand, so the air doesnt blow it around?

2) hole above sand for the pipe, (imbetween brick) i got one today, its about 5 ft long and very thick, about 2 inches on the inside.

-inserted at an angle, and supported by logs, (half moon cuts in the logs for pipe) hair dryer end above the ground 3 feet or so

-refactory lining the hole in the trash can where the pipe fits.

-slit in pipe for air flow control, metal bar with a few differant hole sizes, maybie use smallest hole size when i dont need air, 

just to keep the pipe from getting hot

3) cut/file firebrick to line can so they fit together, 

-sand/clay mix behind the bricks (would firebrick powder/clay work better?)

4) room for coal, but 2 firebricks on bottom to hold crucible

5) the firebrick is brittle, so protect it and insulate with refactory

6) insulate lid, attach with hinges to make things easyer.

7) if clay/sand mix or firebrick powder/clay behind the brick, let it dry and cure with lightbulb

8) after the firebrick has the refactory coating, dry (week)/lightbulb again

9) small heat source for some time to steam out the water..

Link to comment
Share on other sites

I live near cooperstown/oneonta NY..

there is a farmers museum that offers a blacksmithing workshop.

i have funding, just have to sign up and go.


The propaine grill is pretty big, to use as a Forge...

i was thinking clay/sand, or firebrick powder/clay, or sand/firebrick powder/clay 1:1:2 more clay to hold the sand and powder.

line it with that.

when i cook a burger, a lot of heat gets out,

if i coat the inside with homemade refactory, im hoping to keep more heat in and have the propaine work more affectivly.

Link to comment
Share on other sites

Sigh.......got a long ways to go boss.  Best chance is read a lot of material, and take some classes. Still got to build your knowledge base. Not to offend, there's a huge amount to learn. I definitely have much to learn and I've been playing with and reading about metal for the last 10 yrs. S' a reason they use material engineers at iron plants and such....


A grill will make a lovely forge......just not with any of the equipment that comes with it. It does make a nice shell for a coal forge. The propane burners that are in it won't even come close to forging temps, much less melting temps of anything you would want to make a knife out of. A propane forge needs a burner that is built especially for that purpose.


Carbon and heat treating..........hmmmm, info on carbon all over the place on here, read some of the beginner forums and the knife making class forums. Short version - unless you have mad skills, knowledge, and more equipment than most of us are able to purchase or build, you won't pour good knife making steel. You might eventually pour cast iron with a cupola, but it makes lousy knives and is orders of magnitude harder than anything you're going to do with a coffee can furnace. You can make knives from other metals, but the first time you try an aluminum knife (or bronze for that matter), especially a homemade one, you're going to be very, very dissapointed.


Basically, if you want to make knives, you'll want to forge them. You'll end up with a much better product, with far less work, and not have to spend years of your life getting to the most basic stage. (now to get really good, well......I'm not there yet, but I've only made a dozen or so.......they say after 50, you'll probably be a lot better. :D Still, pretty happy with the ones I've made, and they're usable. Even the ones from my "pile of shame".)


Read the knife making classes, join a blacksmithing group, and don't give up! Build a 55 forge, and you could be wrapping 550 cord around a hilt in a matter of days.

Link to comment
Share on other sites

2 setups..

Im thinking melting/casting metal for a knife in the foundry might be harder/more dangerous than,

buying a piece of steel, heating it in the forge, and hammering it on an anvil.

i dont need to have the grill up to melting temps, cause i'll have the foundry.


i should probably start with the grill forge, and play around with that before attempting to melt/cast metals.

(in a trash can foundry)


What would u suggest for the Grill Forge, (since i should probably make my trash can foundry after a local blacksmithing workshop)

if i wanted to use propaine, is there a special burner i can buy to replace the factory burner?

and should the shell be coated in insulation, to keep the heat in?

so i could use coal for the foundry and propaine for the forge.

Or as u suggested, should i just use coal for both?

Link to comment
Share on other sites

I found a 'Blacksmithing Intensive Worshop' in my area, just waiting for them to get back to me..


Blacksmithing Intensive Workshop
Monday, November 18, 2013
Tuesday, November 19, 2013
Wednesday, November 20, 2013
Thursday, November 21, 2013
9:00 a.m. - 4:00 p.m.

This class allows two students to completely immerse themselves in learning traditional core Blacksmithing skills. It is responsive to what the students need to learn, and will cover the core skills of our intermediate classes, tool making, and also introduce forge welding. The four day format allows skills to be learned, practiced, and perfected by repetition.

Link to comment
Share on other sites

For a foundry, I like lump charcoal with forced air. .Coal for a foundry........would be, umm......REALLY hot and intense....more appropriate for cast iron. Which would melt you're refractory. I've used propane, it's slower, but doesn't oxidize to badly or blow "fire fleas" out the vent hole. For forging, bitumous "metallurgic grade" coal. You don't necesarily have to use refractory with a grill forge, but you might want to "clay" the bottom and sides with a mix of fireclay, sand, and wood ash. Several ways to do it. Another nice variant would be a 55 forge. Plans available in the forums here. Brake drum or disk as a firepot - with a rotor, you can build up a clay firepot....


2 inch pipe makes a nice tuyere. A tee with a long nipple going to your air source; a lot of people use a hairdryer with an air gate or a dimmer switch.


Lots of possible variants. Made mine first in a lawnmower.


If you want propane burners, lots of commercially available products, or can build one fairly simple. Get a GOOD regulator, use safety cutoffs, and keep rubber hoses well away from heat sources. If you build one....well, I believe frosty's plans are on here somewhere, or you can hit him up on pm. Good design. Note that a propane forge is mostly enclosed, as opposed to a coal forge.


Classes are good. I'd also look for a local blacksmithing group. You can learn more by watching someone experienced in one session than you'll pick up in a month of youtube vids.


Like I said, lot of beginner blacksmithing tips, classes and the 55 forge plans in the forums. Many of them pinned.

Link to comment
Share on other sites

Thank you :) You answered a lot of my questions.


The propane grill i have is large, and has a large oval burner at the bottom, with an air hole circle on each side of the grill walls.

with the clay mix, (was thinking just about the whole inside)  would the stock burner still be insufficient to reach temps,

just hot enough to make the metal plyable if it was well insulated?

Not sure why the stock burner wouldn't work.. (not melting metal, just heating)

Or is it that when the grill is insulated and hotter than cooking burgers the burner wont hold up?


Gonna wait until i take the class (its a 2 person class, so it will be custom tailored to my needs, and the other persons with hands on learning) before i attempt to melt metal, and might wait on building the foundry as well.


But id like to start heating/reshaping-working metals with the grill a lot sooner (since not liquid metal and not as hot, or complex thought it would be safer)


I have a piece of thick/wide steel i could use as a temporary anvil, strap it to 3 large logs maybie, (since its like 5 feet long, about 7 inches wide and around 2 inches thick)

I have a heavy hammer maybie 3x the weight/size of a regular hammer, and my dads got a face shield i can have... 

if i got a lawnmower blade off my broken mower, could i get it hot enough to be plyable, and shape it on the makeshift anvil?

or cut it in half at the middle to make 2 knives?


-thanks again, -Ian

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...