Introduction: Itty Bitty Mini Forge

Picture of Itty Bitty Mini Forge

Long time fans of blacksmithing, we delighted in having the Florida Artist Blacksmiths Association demo at our recent Gulf Coast MakerCon event in March. We were equally delighted to find a way to bring a little bit of the blacksmith arts into our suburban garage, when we came across this great video by NightHawkinLight, on how to make a Soup Can Forge. Intrigued, we looked around for some written step-by-step instructions and didn't see any, so we hope NightHawkinLight takes it as a compliment that we documented our little build and share it here, as perhaps a companion piece to his terrific how-to video, which we've included here and highly recommend you watch in its entirety first.

Our build time, start to finish: about an hour and a half, mostly 'cause we were klutzy with the fireproof lining mixture.

Step 1: Assemble Your Supplies

Picture of Assemble Your Supplies

You'll need:

  • A can - we used a 28 ounce crushed tomato can, sans the crushed tomatoes. We chose to leave the label on for a Warhol-esque effect.
  • A block of wood
  • A black iron pipe nipple - 1/2" x 2"
  • Two L brackets
  • A pair of wood screws to afix the brackets to the block of wood
  • A pair of small metal screws with washers and nuts to afix the can to the L brackets
  • A small bag of sand
  • A box of plaster of Paris
  • A gallon ziplock bag to mix the sand and plaster
  • A standard propane torch with a spiral flame nozzle
  • Some water
  • Safety glasses
  • Fire Extinguisher - just in case

Step 2: Prepare Can

Picture of Prepare Can

Drill two holes, about a half inch in from either end of the can.

On the opposite side of the holes, about an inch from the back of the can, drill a 1/2 inch hole for the black iron pipe nipple, at a slightly downward angle.

Step 3: Fasten L Brackets to Wood Block

Picture of Fasten L Brackets to Wood Block

Measure out your brackets against the length of your can and where you drilled your bracket holes in the can.

Step 4: Affix Can to Brackets

Picture of Affix Can to Brackets

Use metal screws with a washer and nut and fasten securely.

Step 5: Attach the Pipe Fitting

Picture of Attach the Pipe Fitting

Just screw it in. It should all look like this.

badideasrus added useful tips in the comments, shared here:
"i like this. it's simple and easy. a note though! most of what i read indicates that the angle the pipe enters the forge is important. you want to aim the flow so that it lines up with the circular cross section, so that you get a spinning flow of fire. (bleh, so much harder to say with words what a picture would explain in seconds...)

"make the pipe tangent with the inner chamber, so that it flows round and round, instead of straight into. this keeps fuel inside longer, and supposedly makes the forge burn hotter (i think it keeps heat in too) (this shows basically what i'm trying to say XP)"

Thank you badideasrus!

Step 6: Make & Pack Your Fireproof Lining

Picture of Make & Pack Your Fireproof Lining

Mix equal part sand and plaster of Paris in a gallon Ziplock bag, with enough water to make a moist clay consistency. It's a little too crumbly in this photo, and not quite enough. This was actually the hardest part for us.

We used a 12 oz plastic cup for measuring and based on that would recommend 3 cups each of sand and plaster, and about 1- 1.5 cups of water.

You have to work pretty quickly because the stuff starts to set up fairly fast, and starts getting crumbly.

Pack the mixture in firmly, until the can is about 3/4 full, then dig out a 1.5 inch diameter cavity (we used a plastic spoon), leaving about 3/4" plaster/sand lining the can.* Carve a wider hollow towards the back (bottom) of the can, to create a better heat retention area.

Run a tool, or the back of your plastic spoon through the iron pipe nipple to clear out the plaster there. Wipe the outside of the whole thing clean with a wet paper towel, and then let it sit for a half hour.

*Alternatively (it occurred to us later), you can probably stuff the nipple with paper, and insert a toilet paper tube into the center of the can, or something similar, and pack the plaster in around that, then either remove it or let it burn when you turn on the torch.

Step 7: Fire It Up and Dry 'er Out!

Picture of Fire It Up and Dry 'er Out!

Insert the propane torch nozzle into the pipe nipple and light 'er up! If the air holes on the nozzle are near the tip of the nozzle, make sure they're not covered. Your itty bitty forge will burn cold for about 10 min. or so, until the last of the moisture in the fireproof lining is burned off, and then you'll start seeing the classic red glow of a nice hot forge.

Step 8: Forge Away!

Picture of Forge Away!

Now you can start doing some small scale metalsmithing and glass forging.

And those are whole new how-tos! We have some ideas and hope to share some of those back here soon.

Have fun! And thank you NightHawkinLight for getting us started!


jcolee (author)2014-12-24

I ended up building one for my brother as a Christmas present. I accidentally put the nipple on the opposite side as instructed, but I hope it won't affect function. Even if it sits on the shelf, it looks pretty cool. I think I'll show him your knife instructable and he'll probably have a go at it.

Happy Holidays! Thanks for the gift idea.

EurekaFactory (author)jcolee2014-12-26

This is fantastic to hear! So glad you made one as a gift. :-) It shouldn't matter on the nipple placement, as long as it's still positioned in the back. I don't have a knife Instructable, but NightHawInLight does here: Have fun, and thanks for sharing back your build! Happy Holidays!

TheCoffeeDude (author)2015-12-24

I can't wait to try this. Thanks for the awesome ible.

printrbot932 (author)2015-07-22

i will be making mine with a steel fire extinguisher tube that i cut in half how long should the can be to make it into a forge?

EurekaFactory (author)2015-06-17

Lots of folks have asked about "crucible" type versions of this build. Check out this new Beer Keg Metal Melting Furnace. It might be just the thing!

You are too kind... The soup can forge is perfection. Simplicity and elegant design...

ToggleSwitch made it! (author)2015-06-07

I went ahead and tried it out and happily it worked! it's a little rough because the fireproofing was a huge struggle for me, but thanks to you and nighthawkinlight (and of course instructables) I now have a working mini forge

Hey, that's awesome! Very cool! Have fun! Thanks for sharing your build.

ToggleSwitch (author)2015-06-03

Will this work with a webbed flame?

Not sure. We use a basic old propane torch. Maybe with a bigger can?

Ok thanks I'll try it out and tell you how it goes

Keep us posted! Thanks for Making it Forward! :-)

Neon_Ivory (author)2014-09-24

I will definitely look into it. I'm just starting the craft, and planned on making the old "railroad track" alternative. But assuming I can find the baby anvil, I'll likely, go for that. Thanks for the quick response!

American Ruin (author)Neon_Ivory2014-09-24

Tandy Leather has them... but you can probably find one cheaper with a bit of research. I use the head of a sledgehammer. I had a friend polish and smooth a side at his shop.

zach.thornton.750 (author)2015-03-17

Can this be done by removing the block of wood and L-straps altogether? By say having it standing up straight for a crucible type setup? Or would it affect the heat distribution/propane tank

Hi Zach - there was some discussion in the comments about trying this and I saw that someone gave it a shot but I don't know the results. In searching on "Crucible" I found some similar ideas: but I think you're right to suspect the effectiveness of the propane heating distribution system with the current set up. I'd be curious to hear if anyone's had any luck repurposing the mini-forge into a crucible.

dovahfinn (author)2015-01-18

If i were to buy a graphite crucible what size would i use in this setup? I plan on building two, one up right, for making ingots and melting/pouring into molds and one for forging like yours.

christophor (author)2014-12-14

I love it. Great job in the forge and the Instructable. I made one nearly identical to yours before I saw this.

I used a new empty latex paint can and a few pieces of fire proof ceramic blanket for the container. For the heat, I used a torch nozzle like yours. Only I attached it by a hose to a big white propane tank from the BBQ grill.

I got a little fariers anvil and set it up just like yours.

Awesome job.

That's a great idea! How's it been working?

Pondering_Pig (author)2014-10-28

How long does the propane last for powering this forge?

Neon_Ivory (author)2014-09-24

Thank you, @Amercian Ruin I'll look into it. The sledgehammer is very clever

American Ruin (author)2014-09-24

This is awesome. I've been meaning to branch out into metal work, and this is how i'm gonna start!

Neon_Ivory (author)2014-09-23

Where did you GET the anvil?

EurekaFactory (author)Neon_Ivory2014-09-24

We've had the anvil forever, handed down in the family. Further down in the comments somewhere, there's a discussion about it, but the short version of that is that it looks like you can get little 2 lb. anvils like ours in leather working supply shops and other craft shops.

mist42nz (author)2014-07-10

what kind of temperature do you think you can get to?
I'd love to have something that could melt copper & brass for amulets.

GregC1 (author)mist42nz2014-08-11

no way in hell. built one to see for fun, useless. unless you just want to make some metal kinda hot and not really hot enough to forge anything bigger than a pencil.

EurekaFactory (author)GregC12014-08-11

Small can, small items; bigger can, bigger items. But "for fun" is what it's for. Probably need a more professional arrangement for melting copper and brass, but certainly worth tinkering with to try, I'd say. Really, though - it's just a tomato sauce can with a fireproof lining made of plaster of paris and sand, not a professional forge. It's a proof of concept experiment with some very rudimentary forging capability.

EurekaFactory (author)mist42nz2014-07-10

Hoping someone will have answers for the glass, copper and brass questions - We're curious, too! Just checked over in the Communities section, and in "Answers" and didn't see much on either of these topics, so definitely something worth exploring further.

I'm not sure about glass, but I have plenty of information on metals and their properties regarding casting and forging.

I have done casting, and I can tell you brass and copper both require high temperatures that this type of forge is not capable of achieving. You can melt aluminum and use it for amulets, but it sure won't look like brass or copper.

jscanlan (author)mist42nz2014-07-16

Try turning it on end and use a crucible I think that would work

david.brookes.186 (author)2014-07-31

I have made these before and they are a project doomed to futility. The lining will crumble in about 1 to 2 months if you use it with any excessive heat at all.Air pockets will form it after use (it cooks it, and the plaster of paris is actually what crumbles and overheats.)and the chemical composition just falls apart.

Appreciate the insight and experience. But we're not expecting sophisticated, or long term endurance from a spaghetti can forge. It's just a proof-of-concept, fun-to-tinker with project and we've learned a lot from it. It's obviously no substitute for a real forge nor is it intended to be. It's certainly been instructive though!

petawawa (author)2014-07-26

Would it work with a 19 0z can?

EurekaFactory (author)petawawa2014-07-29

Sure - but remember the smaller your can the smaller your furnace and the smaller work area you have.

DaveDoesThings made it! (author)2014-07-26

Works great! Tomorrow it's time to try a few mods to the interior shape, clean it up a bit, and make myself a spork!

(photo shows first burn, still not hot, was having issues with torch going out because of wind hitting the air holes, fixed, better/hotter now)

Awesome! Congrats!

jscanlan (author)2014-07-16

Would refractory a better choise? I know plaster of paris and sand is cheap but a better quality material in the chamber might last longer and be easier to work.

it will work better, but it is quite costly. Having experience in casting and forging, I prefer Koawool, a flexible, high resistance insulation for furnaces.

ghost11 (author)2014-07-17

this will be a fun project to make. I've always wanted a forge but they are big and I just want one for fun.

Chuck Stephens (author)2014-07-16

Wow! Now your all set to be a ferrier for shetland ponies.

epicalien (author)2014-07-14

I love the tiny anvil

EurekaFactory (author)epicalien2014-07-14

I think we all do. What's not to love about a tiny anvil?! :-)

padbravo (author)2014-07-08

someone could add info on that?

neffk (author)padbravo2014-07-14

Hot work is usually quite involved. I'd take a class on it, to try it out, without having to buy/make a lot of equipment.

eruger (author)padbravo2014-07-11

The only glass work that I am familiar with is neon tube-bending I did in art school, and watching the flame workers who make the little ornaments for tourists, but in both cases, a propane flame in the open was plenty hot enough, and anything more elaborate was used to heat a larger area more evenly. So this setup might be perfect if you want long graceful bends, and I think it may be good for blowing small bottles or such. For the very important annealing process that others mention here however, what you need is a kiln that starts out below the temperature where the glass starts to glow and then cools down slowly to room temp, usually overnight. That's usually done with electronic controls or some poor apprentice loosing sleep. People have also accomplished this with an oven and a fire that slowly cools as it burns through its fuel. Without annealing, glass that has been fine for months can practically explode if it's lightly tapped the wrong way.

padbravo (author)eruger2014-07-11

hahah! that is a good one! the "poor aprentice"! medieval times?

eruger (author)padbravo2014-07-11

You would be amazed at how primitive a lot of glass and metal crafts
still are, even in highly industrialized places! They are also some of
the last bastions of medieval-style apprenticeship! Like a bronze
foundry, where a 1st century roman craftsman would only need a day or
two to catch up with the improvements, and the new guy is still often
unpaid, or may even be paying for the privilege of learning on the job.

Gelfling6 (author)padbravo2014-07-09

I'd say it's possible to get it hot enough for small rod glass, BUT..... You might need a similar annealing oven to slowly harden the object afterwards.. I've melted beer-bottle glass with a propane torch, but it usually shatters if allowed to cool too quickly.

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Bio: At the Eureka! Factory, we love making things, and thinking about things, and learning about things, and enjoy helping empower others to a curiosity driven ... More »
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