Hi all, 

I have searched and not found a satisfactory answer to my question. Which is: Am I nuts to think I can build a good propane forge out of a 5 gallon steel drum that originally held turpentine? It is 10.5” in diameter and 13.5” high.

it has a bung hole and I can flush it out before cutting, so I’m confident I can do it safely. I guess my question is, is the size and shape conducive to making a forge that I can get up to welding heat.

Some background: I’m a woodworker/toolmaker. I’m not making knives. I have an atlas forge and I love it, but the size is limiting  I would like to have something like a 5-6” diameter opening after all the insulation is in.

if there’s a better way to go about this, I’m all ears. Thanks!

 

 

 

 

Sure, there are a lot of proven cylindrical forges about the size you're asking about and they're covered pretty thoroughly in the "Forges 101" section of Iforge. The link is under the IFI home page just scroll down till you find it. Then surf the subjects till you find one about cylindrical forges and again till you find a subject covering what you're looking for. 

We used to reply more directly to forge build questions on the open forum but folk started just asking and not even trying to find the info themselves. A number of us have answered similar questions, often having to wring basic details from the asker. I've been yelled at and called names for not JUST answering the question.

The short answer to your question is, Yes.  Bear in mind, I have zero idea what you want to make so, a can that size can indeed be made into a propane forge, is as meaningful an answer as I can give. 

Same for building burners, I posted a how to for the T burner and another for a naturally aspirated ribbon burner in the extensive Burners 101 section. They are there and illustrated, AFTER you've read them I don't mind helping trouble shoot but that's it. 

I'm not blowing you off or dissing you, I'm offering good advice.

Frosty The Lucky.

13 minutes ago, Frosty said:

Sure, there are a lot of proven cylindrical forges about the size you're asking about and they're covered pretty thoroughly in the "Forges 101" section of Iforge. The link is under the IFI home page just scroll down till you find it. Then surf the subjects till you find one about cylindrical forges and again till you find a subject covering what you're looking for. 

We used to reply more directly to forge build questions on the open forum but folk started just asking and not even trying to find the info themselves. A number of us have answered similar questions, often having to wring basic details from the asker. I've been yelled at and called names for not JUST answering the question.

The short answer to your question is, Yes.  Bear in mind, I have zero idea what you want to make so, a can that size can indeed be made into a propane forge, is as meaningful an answer as I can give. 

Same for building burners, I posted a how to for the T burner and another for a naturally aspirated ribbon burner in the extensive Burners 101 section. They are there and illustrated, AFTER you've read them I don't mind helping trouble shoot but that's it. 

I'm not blowing you off or dissing you, I'm offering good advice.

Frosty The Lucky.

Hey Frosty,

Thanks very much for replying. I didn’t think for a moment that you were blowing me off. I did google and youtube searches, but stupidly did not think to check “forges 101” and some of the other threads (right here! Duh.) so thanks for cluing me in. I will dig into those threads and educate myself. 
You’re right, I didn’t mention what I want to make. Holdfasts, a chair maker’s scorp/inshave, a riving knife (about the size of a cleaver), stuff like that. Nothing terribly difficult for a real blacksmith, which I’m not. But not doable with my current setup. I’m sure I’ll think of 50 more things I want to make, once I’ve ticked off a few of the items on my list. 
But anyway, thanks for the help. 

Sorry if I came off harsh, I'm currently trying to find out why rates on several things jumped significantly Oct 1 and trying to find someone I can just ask is laughably futile, I don't text and they don't talk. It makes me short tempered.

Pay attention to rigidizing ceramic blanket, it's a serious health issue, think mesothelioma serious. Home made works as well and is significantly less expensive than commercial.

The problem with google, youtube, etc. searches is none of the posts are vetted and often dangerously wrong. The only expertise necessary to be an internet expert is a cell phone camera and access.

Sorry, I'm still simmering from an ongoing experience with billing. <sigh>

Frosty The Lucky.

People have even used popcorn tins; they seemed to be all the rage a few years back. Personally, I think five gallon drums are thick enough, but popcorn tins...not so much.

If you get tempted to mount your burner at top dead center, and pointing straight toward the forge floor, then you would be wise to use two 1/2" burners in place of a single 3/4" burner, so that the flame can finish combustion before it impinges on your work.

So, why would anyone do that, after we have all said not to? The thinner the forge shell the tougher it becomes to mount burner ports at an acute angle. Then, the temptation to just use electrical conduit's hardware and call it good gets very strong 

8 hours ago, Mikey98118 said:

People have even used popcorn tins; they seemed to be all the rage a few years back. Personally, I think five gallon drums are thick enough, but popcorn tins...not so much.

If you get tempted to mount your burner at top dead center, and pointing straight toward the forge floor, then you would be wise to use two 1/2" burners in place of a single 3/4" burner, so that the flame can finish combustion before it impinges on your work.

So, why would anyone do that, after we have all said not to? The thinner the forge shell the tougher it becomes to mount burner ports at an acute angle. Then, the temptation to just use electrical conduit's hardware and call it good gets very strong 

Thanks for the info Mike. Now that I’ve done some research, I see that you literally wrote the book on this. I’ll get a copy before I proceed any further. I’d like to avoid two burners if possible, but I’ll do two if it’s needed. 

OK, now a much more specific question.

I'm considering a forced air burner (sorry Mike and Frosty). One reason is that I have a blower left over from forge #1 (charcoal brake drum forge, retired a few years ago). I'd upload pics but every time I try I get "unknown server error." Anyway, the blower is similar to this one:

Removed commercial link...

But mine is a little more powerful, 1.35 amps and 3000 rpm.I'll guess about 100 cfm. I think I paid about $30…15 years ago. Jeez, inflation.

So, would this be an appropriate blower? I also have a brass gate valve and some cast iron pipe. Seems like that would get me most of the way to a burner, without spending any money, but if the fan is not optimal, I don't want to use it.

 

Edited October 6, 2025Oct 6 by Mod30
Remove commercial link.

Yeah, that's way too much blower. It's getting late in the season so 12v and 120v mattress inflaters should be available for a couple dollars tops, if not Wally world usually carries them for under $20 if they haven't closed them our already.

You'll still need a spill type waste gate because these are way over powered for a couple few 3/4" propane blowers.

I've used them for coal forges and the easiest way to control the air flow is the simplest waste gate ever. Simply place the output of the blower where it isn't blowing directly into the tuyere pipe or air supply for a burner.

Unlike a naturally aspirated burner adjusting the heat on a gun (blown) burner requires the operator to adjust fuel and air flow to keep them balanced.

There are tradeoffs whichever type you choose. NA burners like Mike and I make require tighter tolerances and more shop skills but once tuned you don't have to fiddle anymore, turn the propane psi up and it induces more air. A gun burner is easy to build but you have to tune the flame every time you turn the heat up or down and unless a person spends enough to buy a commercial propane gun burner you MUST retune the flame every single time you change the heat output heat. 

Neither Mike nor I have a dog in the fight about what you choose, we both just like making HOT fire and the necessary technical details of making NA burners is more fun for born tinkerers.

Frosty The Lucky.

48 minutes ago, Frosty said:

Yeah, that's way too much blower. It's getting late in the season so 12v and 120v mattress inflaters should be available for a couple dollars tops, if not Wally world usually carries them for under $20 if they haven't closed them our already.

You'll still need a spill type waste gate because these are way over powered for a couple few 3/4" propane blowers.

I've used them for coal forges and the easiest way to control the air flow is the simplest waste gate ever. Simply place the output of the blower where it isn't blowing directly into the tuyere pipe or air supply for a burner.

Unlike a naturally aspirated burner adjusting the heat on a gun (blown) burner requires the operator to adjust fuel and air flow to keep them balanced.

There are tradeoffs whichever type you choose. NA burners like Mike and I make require tighter tolerances and more shop skills but once tuned you don't have to fiddle anymore, turn the propane psi up and it induces more air. A gun burner is easy to build but you have to tune the flame every time you turn the heat up or down and unless a person spends enough to buy a commercial propane gun burner you MUST retune the flame every single time you change the heat output heat. 

Neither Mike nor I have a dog in the fight about what you choose, we both just like making HOT fire and the necessary technical details of making NA burners is more fun for born tinkerers.

Frosty The Lucky.

Thanks Frosty, this is so helpful. Your list of pros and cons has convinced me to ditch the forced air idea. As a toolmaker and former machinist, I’m not worried about precision. Not having to tune the burner every time is a big plus. So is not needing a power cord, and having a smaller, lighter forge. Now I just need to decide whether to build the Frosty or Mike burner. 
One more question, if you don’t mind. Suppose I went with the Frosty burner. Is there any reason not to have two burners? I figure the volume will be right around 325 cubic inches, bumping up against the limit of one burner. Is there any downside to having two (other than cost, which is pretty low)?

325 cu" is well within a well tuned 3/4" NA burner's range. But there is more to selecting and positioning a burner than forge volume, shape is a significant factor. Subtracting 4 1/4" from the diameter and length and tip tapping my calculator says you'll have about 240 cu/in chamber roughly 5.75"dia x 9.25" L.

While not awful it's pretty long and narrow which means uneven heat in the chamber, even if positioned to produce a strong swirl. It WILL get plenty hot enough to weld though, a 3/4" burner is about 50% more than necessary.

For heat treating you want to be able to make even heat in the chamber it's not good if the center of your 8" blade hits yellow before the ends reach low orange. 

Two well tuned 1/2" NA burners mounted evenly spaced and mounted tangential to the top of the chamber provides almost exactly the same heat output as a single 3/4 but the flames are equal distance from the ends and each other, a strong swirl means the chamber will heat very evenly. The flame impinging the lid over the work gives the flames as much distance as practical to finish combustion and help prevent scale formation.

The problem with HOT steel scaling up is any contact with oxygen will cause oxidation of the steel almost instantly at orange heat so the more we can prevent it forming in the forge the longer you have once you remove it. 

FYI, Mike and I do burners differently so we aren't mad when we argue here. We know the difference between arguing points and fighting though we sometimes disagree pretty strongly. It's always good.

Frosty The Lucky.

 

Steve,

Frosty has it right. Neither one of us cares what kind of burner people choose; only how well it works. Frosty admires the practical, and I like to push the envelope. But we agree that whatever it takes to get the job done is the main point. A quarter century back, we both reached the opinion that fan-blown was not a necessity to get a burner hot enough. Back then, the common myth was that naturally aspirated burners would just never get a forge to welding heat. Both of us called that bunk, because that's what it was; not because we with thought fan-blown burners were evil of something.

  The other extreme is to think fan-blown burners are somehow second rate burners, which is equally bunk. My favorite burners (at present) use fans; just not to induce air. I use fans to induce vorticity. But, this doesn't mean I think using fans to induce air is somehow wrong; it just isn't what I'm looking for ...right now. If I ever get around to making ribbon burners, that will change.

  The bottom line is that "one shoe doesn't fit all." Several people on IFI have developed totally cool burners, which have little in common with Frosty burners, or Mikey burners. So, whatever works best for-what-you're-doing is best 

15 hours ago, Frosty said:

325 cu" is well within a well tuned 3/4" NA burner's range. But there is more to selecting and positioning a burner than forge volume, shape is a significant factor. Subtracting 4 1/4" from the diameter and length and tip tapping my calculator says you'll have about 240 cu/in chamber roughly 5.75"dia x 9.25" L.

While not awful it's pretty long and narrow which means uneven heat in the chamber, even if positioned to produce a strong swirl. It WILL get plenty hot enough to weld though, a 3/4" burner is about 50% more than necessary.

For heat treating you want to be able to make even heat in the chamber it's not good if the center of your 8" blade hits yellow before the ends reach low orange. 

Two well tuned 1/2" NA burners mounted evenly spaced and mounted tangential to the top of the chamber provides almost exactly the same heat output as a single 3/4 but the flames are equal distance from the ends and each other, a strong swirl means the chamber will heat very evenly. The flame impinging the lid over the work gives the flames as much distance as practical to finish combustion and help prevent scale formation.

The problem with HOT steel scaling up is any contact with oxygen will cause oxidation of the steel almost instantly at orange heat so the more we can prevent it forming in the forge the longer you have once you remove it. 

FYI, Mike and I do burners differently so we aren't mad when we argue here. We know the difference between arguing points and fighting though we sometimes disagree pretty strongly. It's always good.

Frosty The Lucky.

 

Frosty,

Ok, two half inch burners it is. Thanks again for taking the time to explain all this so thoroughly. I think I’m out of questions for now. It’ll take some time to assemble my materials and get this thing built, but I will definitely keep you guys updated. With pics, if I can figure out the “unknown server error” thing.  I think I have a solid plan now (thanks to you and Mike), and that’s something. 

9 hours ago, Mikey98118 said:

Steve,

Frosty has it right. Neither one of us cares what kind of burner people choose; only how well it works. Frosty admires the practical, and I like to push the envelope. But we agree that whatever it takes to get the job done is the main point. A quarter century back, we both reached the opinion that fan-blown was not a necessity to get a burner hot enough. Back then, the common myth was that naturally aspirated burners would just never get a forge to welding heat. Both of us called that bunk, because that's what it was; not because we with thought fan-blown burners were evil of something.

  The other extreme is to think fan-blown burners are somehow second rate burners, which is equally bunk. My favorite burners (at present) use fans; just not to induce air. I use fans to induce vorticity. But, this doesn't mean I think using fans to induce air is somehow wrong; it just isn't what I'm looking for ...right now. If I ever get around to making ribbon burners, that will change.

  The bottom line is that "one shoe doesn't fit all." Several people on IFI have developed totally cool burners, which have little in common with Frosty burners, or Mikey burners. So, whatever works best for-what-you're-doing is best 

Mike,

Thanks so much for the additional thoughts and perspective. Neither you nor Frosty tried to persuade me to go with NA vs forced air, but the listing of pros and cons persuaded me that NA is the better way to go, for me, at this point in time. 
 

I’m going to read through your book and then decide whether to build a Mikey or Frosty T. Whichever one I choose, the additional perspective from studying both types will help, I’m sure. Either way, I think two half inch burners is a good plan, based on what both of you have said. 
 

This discussion has been a huge help. I still don’t know squat, but I know way more than I did, thanks to you guys pointing me in the right direction. Thanks again!

I think the Iforge ITs are getting the bugs in the last update ironed out, my upload speeds are getting better, slow but better. Remember to resize photos to 1,000 kb. or less. That file limit may have changed I don't know. I'll have to ask.

When I developed the T burner my aim was a burner that was inexpensive and could be built using basic shop tools and skills so people could build a basic forge and give smithing a try without breaking the bank. It wasn't until Mike and I started talking here I discovered I'd developed a low velocity burner. The flame exits the burner moving about as slowly as possible without burning back into the burner and a low velocity flame stays in the forge longer transferring more energy to the liner. What heats your work is IR re-radiated from the incandescent yellow forge liner, not the flame directly. 

Keeping the flame in contact with the forge walls as long as possible is why directing it to swirl in contact with the liner is so beneficial.

An update years ago pretty much deleted picture files and it looks like this latest one wants to do it again. IF I can make MS windows let me I'll see if I can resend my original, illustrated T burner instructions from the onboard memory. A number of things have changed some significant since I published those plans but I'll be more than happy to talk you through the changes. The changes made the build faster and easier believe it or not. 

The skill requirements are basic, measure accurately, drill and tap straight holes and evaluate a torch flame for adjustment. Tools and equipment are really basic as well, a drill, bits to pilot the tap to mount the jet, bit and tap to drill the jet mount fitting to accept a mig contact tip. If you have or have access to a drill press you're golden if you have a machine lathe you have a golden Cadillac for the build. I can build a T burner in my lathe in about 15 minutes without turning it on. Yes, with a reasonably sharp drill bit you can drill through 3/16" of cast iron in a T fitting by hand turning the chuck in maybe 30 seconds. Same for chasing and tapping the brass fitting for the propane supply. I do both steps without removing the T fitting from the lathe, doing it this way aligns everything straight down the center of the mixing tube. Alignment is the single most important detail for making an effective burner.

You don't have to thank me for writing this stuff out, it's not like I put activities on hold or anything, I do this in steps when I have a little time. I've written this same basic introduction yak hundreds of times at least and we'll spend more time helping you through the first build. 

I didn't know how effective the T burner was going to be when I adopted and adapted a basic "jet ejector" so someone with basic shop skills and equipment could make an effective burner. Once you get past the basic shop skills angle the main problem folks have is inducing the "right" amount of combustion air for a neutral flame. The easy solution you see commonly is using a small dia. jet and high psi that draws excess air and a choke plate to control it. 

There are lots of uses for a lean flame making a high speed burner the right choice but for blacksmithing on simple steels you want a neutral of very slightly reducing flame. Too reducing means excess carbon monoxide (CO) in your breathable air. Any open flame like your kitchen range let alone a propane forge WILL produce SOME CO but good ventilation will keep it to safe levels. 

Anyway, I adapted the T to maintain the same fuel air ratio at any propane psi. Well . . . it's a very flat curve, in reality the higher the psi the leaner the flame but it never becomes oxidizing. Seeing as the general issue was inducing ENOUGH combustion air I changed the machine from a linear inducer like Mike's or Ron Reil's or many others and adapted the Jet Ejector which are used commercially for drawing a vacuum.

Seeing as one of these things can draw that strongly it was easy to detune one so it drew the basic 18:1 ratio that propane likes for a neutral flame. I chose a T fitting because it's easy to clamp in a drill press using a floor flange and short nipple or chuck in a lathe with a nipple.

Simple, fast and easy. I had NO idea how effective a burner it was going to make, that was a happy accident. 

DANG I think I've talked enough for now.

Frosty The Lucky.

Frosty,

I didn't know the file size limit--didn't see it on the upload page. I'll look for that next time.

I think I read somewhere that Mike's burner was high velocity, but I didn't know yours was low velocity. Good info and more perspective.

I don't have a lathe, but I have a Bridgeport J head and many years experience running it, so I'm all set. 

Your comment "The easy solution you see commonly is using a small dia. jet and high psi that draws excess air and a choke plate to control it"--I think this describes my current (purchased) little knife maker's forge. I was running it at 8-10 psi and not doing very well. Contacted the manufacturer and he told me to run it at 17-20. That works, and I've been able to weld some small pieces, but it sure seems like a lot of gas. I'm not knocking him at all--the forge does what it's supposed to do, and I've been happy. But I'm looking forward to seeing if I can make something that's a little more efficient, for not much cash.

 

I just PMed John and asked about file size limits, we'll both find out. 

I SUPPOSE you can use a vertical mill to make a T burner.  I should be asking you how to do some of this stuff.

With the opening of the borders to anybody, lots of people pick things to reproduce and sell cheap whether they have clue 1 about how they work. Worse, the guy answering email, contact us, or the phone is almost always an office flunky with a list of set answers and knows even less. 

This is a bit of a pet peeve of mine but you don't wat an "Efficient" burner, it probably already about as efficient as reasonably possible. What you and almost everybody else who asks is actually looking for is an "Effective," burner. In the case of an air breathing gas burning appliance, efficient means it is burning all the fuel and converting it to heat.

Effective means it produces heat in a way you need or want. An effective burner needs to be efficient but there's more to it than that.

I know I'm just being as Mike says, "a mr. picky butt" but properly adjusted torches have been apart of my life since I was pretty young, 9-10 or earlier.

Frosty The Lucky.

7 hours ago, Frosty said:

I discovered I'd developed a low velocity burner. The flame exits the burner moving about as slowly as possible without burning back into the burner and a low velocity flame stays in the forge longer transferring more energy to the liner. What heats your work is IR re-radiated from the incandescent yellow forge liner, not the flame directly. 

I totally agree with everything you wrote, and thought your burner flame was a delight. The best part for me, isn't where we agree, but what we both learn something new, when we don't 

Steve,

Buy the book, use the book, and then sell the book. However, you can converse with its author right here, and with others who have built its equipment, and more importantly have changed its details to suit their needs. You should too; it is twenty one years old. People have made improvements. Do not follow its advice on the number of air openings. Instead, always use three air openings. Do not go through all the hassle to make its accelerator (gas pipe and MIG tip) the way I suggested. Take a little extra trouble and expense to use 1/8" schedule #80 pipe.

  High alumina kiln shelves have become expensive in the last two decades, and so I suggest that most people ignore the book's advice about how to go about building a forge floor. Nevertheless, anyone who plans to weld in this forge, should just cough up the dough. There is no easy and convenient way to deal with flux in forges; the best you can have is one or the other. The point of using a high alumina kiln shelve for a floor, is that it easily slides in and out of the forge shell, for easy removal of flux with a wire wheel. 

  But, but, but, what about kitty litter in a stainless steel pan? Its a fine idea...in a box forge, or in a "D"forge (if you're careful to give it a couple inches of vertical walls at its bottom) not in a tunnel forge. And anyone who plans to go this rout is wise to buy the pan first, and build around it, if they want to get the forge right 

  There is no best forge, best burner, or best size for either. If you actually use them much, you will end up with a variety of forges, just like your variety of hammers. Fortunately, not anywhere need anywhere near as many forges as hammers. And just like buying or building hammers, the idea of needing several is kind of a drag, in the beginning. But it only takes a few trips to refill your tank to realize that, like hammers, the right forge for the task is a huge blessing.

  Nor do I think that gas fired forges are the only way to go. I started building them after Kathy retired me at the right old age of fifty-four; she didn't agree with my retirement plan (just kicking off at work) By then, my lungs were in pretty bad shape. However, coke forges are totally cool. We just can't always have our druthers. But you'll find properly built propane forges to be a real gas  

On 10/5/2025 at 7:21 AM, Steve Voigt said:

I’d like to avoid two burners if possible, but I’ll do two if it’s needed. 

No; two burners are not a necessity. I am never satisfied, and always looking for a little more advantage. Two burners allow one of them to be shut down, and an internal baffle wall to be placed in the forge center. Then, the other burner can be run in one-half the forge area; this gives the same advantages as two different forge sizes in a single forge. For instance, a five gallon propane cylinder forge, can replace a two  or three-gallon forge, at will.

  Do many people follow this advice? Heck no; but later on, some wish they had. Building the extra burner, and extra mounting for it, adds little expense (but more work). The first trip to refill your propane cylinder will make it all quite worth while, unless you  always max out your forge capacity; not many do.

4 hours ago, Mikey98118 said:

I totally agree with everything you wrote,

Come ON Mike don't mess with the new guy, he hasn't been here long enough to know when to believe us or laugh!

In all seriousness  Steve it is true, hammer and tongs discussions over things we don't agree about has really improved our "understanding" about burners, flames and the rest.  Little things like Mike making me realize a propane forge is actually a machine composed of several different elements and they all need to balance to operate at peak efficiency for maximum effectiveness.

Life is strange, two guys you'd expect to be rivals got to be pretty good friends BECAUSE we disagreed but both want to know how to make hot flames in as many ways as possible. Not being stuck on our own "way" is one of our closest similarities. Like I've been saying for years, I'd rather "know" I'm right than think I am.

The word "know" is in quotes because I've come to believe we can't "Know" anything, best we CAN do is describe it as accurately as our powers of observation and measurement allows.

If you haven't noticed, I can be pretty long winded.

Frosty The Lucky.

 

6 hours ago, Frosty said:

If you haven't noticed, I can be pretty long winded.

What I HAVE noticed is that there are often pearls amongst all the hot air! 

--Larry

13 hours ago, Mikey98118 said:

 

Steve,

Buy the book, use the book, and then sell the book. However, you can converse with its author right here, and with others who have built its equipment, and more importantly have changed its details to suit their needs. You should too; it is twenty one years old. People have made improvements. Do not follow its advice on the number of air openings. Instead, always use three air openings. Do not go through all the hassle to make its accelerator (gas pipe and MIG tip) the way I suggested. Take a little extra trouble and expense to use 1/8" schedule #80 pipe.

  High alumina kiln shelves have become expensive in the last two decades, and so I suggest that most people ignore the book's advice about how to go about building a forge floor. Nevertheless, anyone who plans to weld in this forge, should just cough up the dough. There is no easy and convenient way to deal with flux in forges; the best you can have is one or the other. The point of using a high alumina kiln shelve for a floor, is that it easily slides in and out of the forge shell, for easy removal of flux with a wire wheel. 

  But, but, but, what about kitty litter in a stainless steel pan? Its a fine idea...in a box forge, or in a "D"forge (if you're careful to give it a couple inches of vertical walls at its bottom) not in a tunnel forge. And anyone who plans to go this rout is wise to buy the pan first, and build around it, if they want to get the forge right 

  There is no best forge, best burner, or best size for either. If you actually use them much, you will end up with a variety of forges, just like your variety of hammers. Fortunately, not anywhere need anywhere near as many forges as hammers. And just like buying or building hammers, the idea of needing several is kind of a drag, in the beginning. But it only takes a few trips to refill your tank to realize that, like hammers, the right forge for the task is a huge blessing.

  Nor do I think that gas fired forges are the only way to go. I started building them after Kathy retired me at the right old age of fifty-four; she didn't agree with my retirement plan (just kicking off at work) By then, my lungs were in pretty bad shape. However, coke forges are totally cool. We just can't always have our druthers. But you'll find properly built propane forges to be a real gas  

Mike,

I’ll take you up on the conversation once I have some legitimate questions. For now, I need to read a bunch more. 
Example: I never even heard of a kiln shelf until this weekend. The maker of my little forge expressly forbids using borax, and I’ve been wondering if there was a solution to that. I’ve been able to do some acceptable hydrocarbon welds but the kiln shelf is a pretty cool idea. 
Re solid forges: my first forge was charcoal, and if I lived out in the country, I would probably just build a coal forge. But in my neighborhood, coal would probably be no-go with the neighbors. And it definitely would be a dealbreaker with the wife! She’s already pretty unhappy when I cook fossil resin varnishes in the back yard—coal forge would be a whole ‘nother level. So propane it is!

They forbid borax flux because their forge isn't properly built and if it has bare fiber insulation it's dangerously unfinished. 

Bare ceramic blanket refractory vitrifies at lower forge temperatures and the now brittle ceramic fibers tend to break off and the sharp little needles blow out of the forge into your breathing air. You then inhale them and they poke holes in the alveoli in your lungs and because they can not be dissolved can cause scar tissue which can  cause cancer. Think mesothelioma, just like silica dust.

Mike, I and others hashed out an effective way of reducing this hazard virtually to zero. First you need to rigidize the blanket. Mike's recipe works very well and is very inexpensive compared to commercial stabilizers. The recipe is Fumed silica in clean fresh water with a drop or two of food coloring. Fumed silica is colloidal meaning it will stay suspended in water and the food coloring marks the ceramic blanket so you know how well you've covered the blanket.

To apply it you first wet the blanket with clean fresh water and a spray bottle. This is known as buttering which is a masonry term and allows whatever you're applying be it stabilizing spray or mortar when laying bricks to bond properly. The wetting dilutes what you're applying slightly so it can flow into all the nooks and crannies. Without buttering mortar or whatever flash dries on contact and it can't bond properly. Make sense?

Once thoroughly rigidized you set it by bringing the ceramic blanket to red heat with the burner, propane torch, etc. This fuses the fumed silica to the ceramic blanket fibers where they cross where the rigidizing mixture collects. This prevents fibers from breaking off and being blown into your breathable. Yes?

Once the rigidizer is cured the next step is to apply a water setting high alumina hard refractory flame face. The last time I checked Kastolite-30-li was by Iforge consensus the best on the market but that was around 2024. Kastolite 30 wants to cure in a 100% humidity atmosphere for full strength and heat resistance. It DOES NOT DRY it cures like Portland cement concrete. Never confuse the two though, NEVER use Portland cement in a forge liner, when it's temp raises to around 230f. the water boils becoming unbonded to the calcite and you get steam explosions called spalling. Spalling tends to blow chips of hot concrete at high velocity around the area. You do NOT want spalled concrete chips on your hide, it tends to stick using the moisture in you to cool. Think being covered in little bitty scalds, 2nd degree burns are to be expected for anything larger than a flake of coarse pepper in size.

Back to Kastolite curing. Ideally you'd submerge it in water for something like 24hrs per 1/4" but I just put a sopping wet hand towel in the chamber and seal it with a garbage bag for a day or two. I don't need full strength or temp range but the abbreviated wet cure stopped checking or flaking. 

Anyway, it is an alumina refractory bonded by a calcite cement. The alumina component is not dissolved by hot caustics the way silicas are. The bubbles are silica spherules that IIRC pass a 100 opening sieve screen, replacing the fines in the refractory normally filled by silica sand. Bubble do two main things being spherical they can move in the hardened refractory allowing it to expand and contract with thermal cycles without cracking. (Heat checking) The second function is forming tiny evacuated cavities in the refractory both lightening it and improving insulation. 

Fumed silica "bubbles" are commonly available from a concrete batch plant and is often to lighten the weight of concrete pumped to upper floors. It makes it easier to pump and lightens concrete floors, etc. without sacrificing strength. Provided the batch plant has a sales office and sells in small quantities.

You can forge weld with borax flux directly on Kastolite hard refractory without the erosion you'd see to standard 3,000f hard fire brick, let alone bare ceramic blanket. Molten borax is a strong caustic and dissolves hard firebrick like warm water on a sugar cube but is like hot water on cotton candy to ceramic blanket.

This is why el-cheapo propane forge makers say not to use borax based welding fluxes, their liners aren't complete.

The last step for a 1st class forge liner is a kiln wash. Kiln washes are originally intended to prevent pottery or glazes from becoming one with the bricks in a pottery kiln. They do however work a treat as a final layer of armor between the steel melting heat in a propane forge and the refractory forge liner. None of the above mentioned refractories is rated for prolonged max temps above 2,600f and that would the the Kastolite, not the ceramic blanket. 

At one time you could buy a zirconia kiln wash from a ceramic kiln supplier without breaking the bank and I haven't checked lately but last time I did it was frighteningly expensive. The upside is zirconia is a common additive to clay to make it more plastic on the potter's wheel and flow better in ceramic molds. Soooo, it can be had from ceramic suppliers, there is one in Seattle from which our club bought it in bulk for about $10/lb plus shipping. Buying it from a local ceramics supplier is silly expensive but you never know.

The problem with zirconia is it needs a binder because it has a very high vitrification temp, IIRC above 4,000f so it requires a matrix that can take forge temps and fuse. An IFI member from the Nederlands Marten I think(?) did some really good experimentation and testing and came up with a good alternative to commercial kiln washes. IIRC the recipe he developed was 95-97% bentone / bentonite clay and 3-5% fine zirconia powder. The zirconia powder is NOT colloidal and settles in a little while so it must be mixed before using. Be forewarned bentonite isn't like anything you've ever messed with, you can't just mix with water and use it. Bentonite distributes moisture to all the clay in the same bucket, sack, etc. Oil well drilling companies have machinery dedicated to mixing mud to specific density. One so it's heavy enough to prevent gas blowing past and venting to the surface, called a "blow out." These are seriously disastrous events, look up "Piper Alpha" for a B A D blow out. 

Drill mud is pumped down the hole before it's completely hydrated where it's forced into cracks in the rock being drilled through, the mud continues to absorb water and expand until ambient pressure stops it. This seals bore holes more strongly than the natural formations.

Anyway, to use it for a kiln wash we have to allow the bentonite time to completely hydrate. Then remix the zirconia you REALLY want to mix the zirconia powder and bentonite clay BEFORE adding water or it'll never mix thoroughly.

Once mixed and aged and the rigidized blanket is "buttered" you can apply the kiln wash with a brush, (thick latex paint is a good consistency) or spread it on at a warm butter consistency. Buttering is very important to get this stuff to bond!

It doesn't take much at all but if you need more than a single coat let it dry thoroughly between coats and remember to butter the dry layer first. Thick coats WILL PEEL as the surface in contact with air will form a skin and shrink as it dries which pulls the wetter contact layer off. This is a Bentonite thing and how it is. 

Once dry fire it up and the kiln wash will vitrify like the glaze on a coffee mug. One of the properties of zirconia is it's very low thermal conductivity so it will absorb more energy from the flame without conducting much to the hard refractory below and it just keeps absorbing energy. This means the zirconia will actually reach temps higher than the flame because it doesn't shed it very well except as radiant energy. Radiating energy is always slower than conduction. And here's where it gets a little funny, because the kiln wash is in contact with itself and the hard refractory under it the only "good" direction to shed thermal energy is 90* or straight back into the forge chamber.

The bentonite clay binder is a VERY high fire clay, something like cone 12 so it degrades very slowly over time.

Sorry that was so long winded but we had some really long discussions about these things a couple few years ago and much of the above is MY reasoning and preference, other folk have different opinions but my liner laughs at anhydrous borax welding fluxes, does not gouge at yellow heat and you can almost touch the shell (outside) of my forge. My forge has 2 layers of 1," 8lb. Kaowool blanket refractory and about 3/8" hard refractory floor and 1/4" walls and lid, kiln washed as described above. It's been retired for a couple years as have I, arthritis makes time at the anvil a several day pain so I laid my hammer down except rarely. Anyway the forge saw regular use for a good 3 years with no signs of erosion.

I sure hope there are some pearls floating on all that hot air Larry.

Frosty The Lucky.

16 hours ago, Frosty said:

Come ON Mike don't mess with the new guy, he hasn't been here long enough to know when to believe us or laugh!

He should embrace the power of both 

What I liked best about the effects of Gas Burners for Forges Furnaces & Kilns was not the popularity of its burners, but the explosion of five-gallon propane cylinder forges all over the internet.

With the marketing of modern insulating bricks and kiln washes, I would like to see an equal explosion of brick pile forges. What is lacking is some gimmick like Mikey burners to draw the newbies attention to them. But, hot burners are no big deal, these days. All that's left is someone with a magical turn of phrase, maybe like...a Frosty, yes?   

Like I was HOPING would happen Nobody found my finished T burner plans posted on IFI. It used to be pinned in the gas forge section, maybe still is. The link follows.

https://www.iforgeiron.com/topic/68340-frosty-t-burner/

I'll be happy to help you with a build if you need it.

Frosty The Lucky.

 

What; no comeback to my straight line, Frosty?