Forges 101

[ThomasPowers]

I have a dedicated set of tongs just for picking up stuff on the floor these days!

[Mikey98118]

 

A very good idea.

[Mikey98118]

120V Angle grinders

When I wrote Gas Burner for Forges, Furnaces, and Kilns, hand held rotary tools were no longer expensive, but that wasn’t yet true of their accessories. The 4-1/2” angle grinders of the day, were really just re-geared 4” grinders being marketed because 4-1/2” grinding wheels were (and still are) far less expensive than the new 4” wheels. Nowadays, 4” flap discs have filled this gap. At the time, these grinders were a little under powered, which made them a lot safer for cutting work than the high-power models being pushed in today’s market.

    Also, that text’s smallest burner was ½”, which is the largest size I deal with now. Times have changed. You don’t need to use a full power angle grinder to build burners and heating equipment.

    But what about people on a shoestring budget? What about using an angle grinder for cutting into forge shells, etc.? High-speed plus high-power still equals high hazard…but hazard levels can be reduced. By starting out with one of the weaker grinders like an old Makita 4” grinder, you can bring power closer to the level of a 3” 280-watt angle grinder (big bucks and hard to find) by reducing it to half speed with a router speed controller; and these are cheap.

    The hazard level can be further reduced by changing out the 4” grinding wheel for a well-used cutting disc (around 3” remaining); is this a perfect solution? No, but it’s a whole lot better than no viable choices, for building the 1/2” burner. As for even smaller burners, forget it.

     Or, you can buy a conversion chuck that allows 4” angle grinders to spin ¼” mandrels, and have the equivalent of an angle head die grinder to work with. Suddenly all the accessories for die grinders and rotary tools will be open for your use, including 1-1/4”” resin bonded cutoff discs. Conversion chucks are regular Jacobs keyed chucks that screw right onto the 10mm threads of 100mm (4") angle grinder spindles; they only cost about $11.56 (conversion chucks for 5/8-11threads found on 4-1/2” grinders are available, occasionally; attempting to use drill chucks on angle grinders for drilling, is a bad idea. These grinders spin much too fast for drilling in steel. But for your needs, these chucks are a workable alternative to no available tool for burner construction. For equipment construction, their torque can actually be helpful

[localsmith]

I thought low psi was a good thing because I had the opportunity to ask a German smith about his forge and he told me he won't run it any higher than 4psi using a 0.035" contact tip in a 3/4" burner because he believes he loses too much heat to the atmosphere with a higher psi. I also live 1 hour away from the local propane supplier so it becomes a multi hour affair to get propane which is why I was looking into increasing my forges efficiency. 

[Mikey98118]

And he could be right, for his burner design. Frosty "T" burners run way different from Mikey burners,

there are lots of other designs, too.What is a low or high gas pressure is different, even in burners of the same design; just not as much as with different designs, with different flow dynamics.

[Mikey98118]

Sanding drums

They are also called “bands” and “sleeves.” Sanding drums provide some cushioning to absorb pounding from run-out, and do smoother work in tubes and pipes than grind stones. But 1/4” diameter drums often slip on their rubber headed mandrels; a dab of gasket seal or thread-locker will ease this problem. So, why do some 1/4” sleeves slip so much; are some of better quality than others?  Obviously, but the problem more often is that some mandrels are much better than others. The smaller the sleeve diameter, the harder it is to find a good enough mandrel for it; one answer to this problem is nut lock drum mandrels, which can apply a lot more force against the sleeve than screw top mandrels: most of them, but not all, have ¼” shanks.

    Why cloth backing is better than paper becomes apparent, once you have a good enough mandrel to apply sufficient pressure to the drum. Cheap drums rapidly fall apart, under sufficient pressure to keep them on the mandrel. The smaller the drum the more the problem  is magnified, because the smaller the drum the greater the pressure needed.

 

A set of lock nut sanding mandrels with 1/8” shanks, along with some higher quality aluminum oxide (on stiff cloth backing) sleeves are available from Homedepot. Note that the nuts have left hand thread, to prevent them from loosening during use, and the rubber is top quality

[Mikey98118]

    If the sleeve falls apart during use, or splits during tightening, the sanding band itself is junk. Nearly all sanding bands, whether sold in accessories kits, individually, or along with a rotary tool, are sandpaper that is covered with garnet or fused aluminum oxide abrasive. Sleeves meant for use on ferrous metals are a harder/sharper form of aluminum oxide abrasive (usually charcoal gray corundum) on cloth bands; but some are zirconia, or even harder synthetic ceramic oxide). You aren’t likely to find them in accessories kits. but finish off the cheaper drums before buying the more expensive variety as replacements. When you’re ready for the good stuff, forget about looking all over the Net for them. Go straight to McMaster-Carr, or some other industrial supplier, and input “sanding sleeves” in their search engine. Google searches will give different results when you input their various names:

[localsmith]

Lot's of good information Mikey. I have tried sanding drums but the glue did not hold up even when they were used in a low speed cordless drill. They were really inexpensive ones which explains why they did not hold up for me. 

In regards to forge efficiency, do you happen to know at what point (when using your style of burner) maximum efficiency is obtained in regards to psi and the time it takes to heat stock up in a given forge? I was thinking about it and was curious if a forge using your style of burner running at 4psi (with no exhaust flame/unburnt gas) to heat a piece of 3/4" Round would use less or more gas compared to the same Mikey burner running in the same forge heating up the same 3/4" Round stock but using a psi of 8 (with no exhaust flame/unburnt gas) to obtain the same heat.

From what I know and have experienced, at 4psi the stock would take significantly longer to heat up and bring up to critical temperature or a low forging heat. On the other hand,the same burner running at at 8psi would take significantly less time to bring up the same 3/4" Round stock to critical temperature or a low forging heat. But I'm not sure if a faster heating cycle is more efficient vs a slower heating cycle. 

I've been curious and trying to figure out if the burner running a higher psi would be less efficient because its pushing heat into, and out of, the forge at a faster rate.

I couldn't find much information regarding optimal psi or stock reheat times when doing google searches on furnaces and optimizing furnace performance. I found some information that pertained to boilers and a few studies have been conducted that purportedly show that high speed burners when used in a boiler that runs off of gas are more effect and use less gas because they lose less heat to the surrounding boiler environment because they are able to pump out more heat and convert water to steam very quickly. 

 

[Mikey98118]

Those are good questions, Localsmith.

Starting with your last point: comparing boiler efficiency, brings up the old saw about comparing apples to oranges. The equipment dynamics are simply to different to be relevant. It isn't that they don't apply, but are such a sore fit as to be useless. Water is a wonderful medium for heat transfer by convection, and convection itself is king in near all aspects of boiler construction. For instance, radiant heat transfer, which I so love to harp on, is pretty much irrelevant in a boiler system.

So, let's go straight at your question. /as to my style of burner, or any other style, two things are key; first that the burner is running well enough to completely burn the gas; and second that it ( or they) is large enough or of sufficient number to heat the equipment high into the incandescent range. Positioning etc., are all subordinate issues; not that they aren't important, but first things first.

Finally, there is no simple answer to your question, because there are too many variables. All you can do is look at your watch, while doing the work, and find out

Others, who actually do blacksmithing, would probably tell you that, once you have the right design and forge size, running properly, efficiency becomes a matter of heating the forge to best match up with you hammer time. To which I would only caution you to keep glancing at your watch for answers. If you love the work, it is all too easy to get lost in a subjective viewpoint--I did that for half a century. There are worse things of course, but there are better things too

[Frosty]

Localsmith: You are making a common mistake and as many times as I've explained it folk STILL make it. 

Doubling PSI does NOT double the propane nor induced combustion air.

It's a logarithmic progression, 2x psi = 4x fuel and induced air = 4x the heat.

Comparing psi with other people is a useless exercise there are too many other variables effecting the burn. Mostly the pressure you are actually feeding your burner. You can't know that unless you have the equipment and do the math. We feed out burners psiG  The G stands for gauge and means that particular pressure is in comparison to the barometric pressure where you're standing. 

If you are that concerned about efficiency buy a flow meter, digital/recording is best for ease of use and start measuring usage vs. work done. 

Frosty The Lucky.

[Mikey98118]

Solid tungsten carbide versus diamond coated rotary burrs: Tungsten carbide is 9 on the Mohs scale, but is much tougher than any crystal, including diamond (10 on the Mohs scale). 1/8” Solid carbide rotary burrs used to be quite expensive, but are bargains these days; why? Because diamond coated burrs are even lower priced. Diamond coated accessories work considerably slower than double cut tungsten carbide, but are much smoother to use, for half the price, or less. The larger the accessory’s head diameter the greater the advantages diamond coating enjoys over solid carbide; which still leaves the advantage with 1/8” diameter solid carbide burrs. However, carbide burrs fling needle sharp debris everywhere. The larger the burr, the harder they’re flung, so the nastier the problem gets. Use rubber gloves to keep the little needles out of your hands. A plastic rain coat is better than cloth, when running the ¼” and larger burrs. Diamond coated burrs just fling ordinary dust particles.

    Double cut carbide burrs are far more likely to create kickback than resin bonded stones or diamond coated burrs, of the same diameters; which is why carbide burrs tend to leave uneven surfaces behind. As the burr diameter increases, so does this tendency, along with the likelihood of kickback violently flinging the tool about; especially in a die grinder.

    “Solid Tungsten carbide” includes the accessory’s shank; this precludes all manner of problems that cheaper carbide burrs, which are silver brazed to small diameter shanks, are prone to; like cutting heads that were brazed out of true axial alignment with the shank; this causes a dangerous wobble. Steel shanks themselves may bend easily, or shatter if the choice of their steel alloy or tempering is wrong.

    Single cut carbide burrs come in two types; large grooves (for use on brass and aluminum), and narrow grooves (for use on ferrous metals); these are slower working then double cut burrs, but far less inclined to create kickback, and are smoother acting. While not so quick as double cut, single groove carbide burrs work faster than abrasive stones or diamond coated burrs.

 

Tungsten Steel: Ads that start out claiming their micro drill bits, or double cut burrs to be tungsten carbide, and then shift to describing them as “tungsten steel” are at least selling something better high-speed steel accessories, Tungsten steel doesn’t wear anywhere near as well as tungsten carbide, but tungsten steel will keep its temper up to 932 °F; not as good as cobalt’s 1100 °F, but more useful than the 400 °F limit of high-speed steel.

    Solid tungsten carbide rotary burrs only come with a maximum of 1/8” diameter cutting surfaces. Larger diameter carbide burrs are only available with brazed heads on 1/8” steel shanks; these often have run-out (they wobble). You can get solid tungsten steel burrs with head sections larger than 1/8” diameter; making an end run around possible run-out problems. Tungsten steel is also tougher than high speed steel. All things considered, they are worthwhile, if far from wonderful. When in doubt about your purchase, remember that tungsten carbide is not magnetic; steel is. Tungsten steel burrs also come with larger brazed heads; a poor use of your money.

 

[Mikey98118]

 

About small high-speed equipment burners

 

Why build small high-speed burners? If you want to produce extremely hot flames—without the expense of adding oxygen, or acetylene fuel—that only comes from accelerated flame speed. This is my view of the matter. Others, whose opinions I value, have differing viewpoints. Whether they are saying half a dozen, while I insist on six, who knows? Only results matter.

    So, what about burner size? Few of us desire a micro forge or jeweler’s furnace, but there are many who want more concentrated heat from their air-fuel torches. A large burner makes a clumsy hand torch; thus, the need for 1/4” and 3/8” burners with intense flames. A 1/2” torch is the largest an average person can handle comfortably, and therefore the largest size I work with these days.

    But these are also equipment burners. So, understand that heat management only begins with how hot flames get. The reason burners are aimed on a tangent, is to cause their combustion gasses to swirl around equipment interiors; creating a longer distance from flame tip to exhaust opening.  

    Obviously, a lengthened exhaust path increases the amount of its hang time. Thus, depositing more combustion energy on internal surfaces. What isn't so clear is that the heat gained isn't added by hot gases blowing an extra foot or two at high speed; it’s mainly due to their continuing drop in velocity over the added distance.

    Combustion gases begin to slow as soon as they leave the flame envelope, but small flames decelerate quicker than large flames. The flames of two 1/2" burners will use the same amount of fuel to produce an equal amount of heat as a single 3/4” burner; but will drop velocity much faster in a five-gallon propane cylinder forge; increasing efficiency, because they can burn faster/hotter without creating a wasteful tongue of fire out the exhaust opening.

    Further efficiency can be gained by placing a temporary partition in equipment interiors; separating it into two spaces, and shutting down one of the burners, when heating small pieces. Something that can’t be done with a single large burner that is centrally positioned.

    The same considerations make two 3/8” burners superior to one ½” burner in a two-gallon cylinder forge from a non-refillable helium or refrigerant cylinder. Two ¼” burners will heat the same space at one 3/8” burner. And spaces can be temporarily partitioned in box forges too.

      Fuel cost is a minor concern in miniature equipment, but faster heating times, and increased portability remain major advantages. Portability? Yes; equipment isn’t all that portable, if it must be fed from a large fuel cylinder.

    Do multiple flame burners (Giberson ceramic burner heads, or homemade ribbon burners) take deceleration even further? Certainly; unfortunately, the burners themselves tend to be large. Over time, compact multi-flame burners will be perfected, but first there must be a lot more interest in doing so. Since this kind of burner provides the most advantage in larger equipment, we could have a long wait. If some of you regard this as a challenge, that is all to the good.

[Mikey98118]

 

Occlusions in the gas orifice

Construction debris must be thoroughly cleaned from your burner’s gas orifice. But, after a short time, any debris in a gas line, or lodged in valves and regulator will be blown into the burner’s gas orifice. After further time, propane (and LPG fuel mixtures) can leave residues of wax and/or tar in your burner’s gas orifice. How long that takes, depends on the quality of the fuel, and how small that orifice is. Whether the flame gets leaner for a while, bent off center, or, or reducing is just pure chance; it could go through all those stages. However, eventually the burner will be snuffed out, when the obstruction completely blocks off gas flow.

    An early symptom of this process is the sudden appearance of a dark spot in the middle of the area of flame impingement on a wall or floor, where the burner is pointed; this is caused by unburnt fuel actually cooling that area down some.

  Remove the gas orifice and blow air through it in the opposite direction of normal gas flow. If you have no source of compressed air, stuff a wire file from a set of torch tip cleaners through the orifice from the exit clear through its entrance. Poke the orifice one time only. You don’t want the file to start enlarging the orifice. Try to catch the obstruction and have a look at it. Whether you see a little black tar ball, general debris, or the remains of a baby spider will tell you how likely the problem is to recur.

    A friend of mine had his burner shut down after about three weeks of running propane from an especially cheap source through it. A single poke through the burner’s MIG tip with a wire file produced a tiny little black tar ball. A smith in Europe found his gas system, and burner orifice lined with what he described as “ greasy waxy stuff,” after a few months of forge use.  

[Mikey98118]

Chokes are a burner’s secondary control: Once upon a time there were two very good reasons for adding chokes on burners; the first being to prevent chimney effects from overheating burners after shutdown, and the second being to vary flame characteristics. As naturally aspirated burners have grown stronger. The popularity of using chokes to alter flame characteristics have diminished somewhat; the technique still works, but is perhaps less useful than it was in the past.

    Burner chokes greatly diminish chimney effects through the burner after shutdown, but might require a secondary control mechanism (such as a washer on the burner's mixing tube), to stop it from overheating from chimney effects between the burner and its portal in to mounted burners. This washer can also serve to control excess secondary air induction, created by the flame, from lowering forge temperatures.

 

[Mikey98118]

Never use an external washer to stop flames from backing up from the forge interior, and overheating the burner; this is the equivalent of using a bandage , when a wound needs stitches. The flame is pushing into the burner portal because of back pressure in the forge. You need to address the problem BEFORE YOU BURN DOWN YOUR SHOP! You may simply need to enlarge the exhaust opening in your forge, or you may have too large, or too many burners for the size of your forge.

[Mikey98118]

To avoid surface cutting problems:

(1)  When starting a cut, be sure the accessory is already turning; do not start, or restart a cut, with the tool still.

 

(2)  Gently lower the disc unto the part surface, with the tool held firmly, and lightly run the disc back and forth on the part surface, next to the cut line, to establish a groove. Deepen the groove by continuing to run the disc lightly back and forth, until it starts to break through the material’s far side; at this point, the groove is called a kerf. Don’t press the disc against the part. Just let the disc do the work.

 

(3)  Always delay actually cutting into the kerf until you have no other choice.

 

(4)  Start and stop the cut short of the end of the marked line, and finish the cut later, with a small diameter disc, for greater control, as these two areas are likely spots to create kickback problems.

 

(5)  Allow the disc to come to a complete stop before removing it from a cut, to help avoid jamming the disc, and creating kickback.

 

(6)  A common cause of kickback is a disc that is moving even a little out of parallel to the kerf (that slit in your part that is made by the disc); the problem is multiplied when the disc is deeply inserted into the kerf. It is safer to only try to cutting through the material, after the disk begins breaking through the part’s far surface.

 

(7)  The only relief from torsion kickbacks is provided by Dremel’s EZ-lock mandrel and special cutoff discs; this very effectively reduces torsional forces, making an end-run around the problem. Save the last 1” of their diameters for surface cutting in problem areas.

 

(8)  Another cause of kickback is the disc bumping into the end of the lengthening kerf. Try to only move the disc counter to the direction that friction inclines it to “walk” along the part, once you start cutting into the kerf; this is to help you to avoid allowing the disc to bump against the end of the kerf; always ease into it, to prevent kickbacks. Aside from cutting through the kerf from the right direction, practical relief from bumping kickbacks is provided by smaller diameter cutoff discs. Dremel’s 420 discs are an economical source of suitable small discs.

 

(9)  When you can, try to cut beside of the cut line, and then grind back to it afterward; this allows you to concentrate on two separate tasks, instead of looking after too many aspects of the cut at one time. After you finish all cuts and remove unwanted sections, then start grinding back to the scribe or ink lines with a small stone wheel, or diamond disc. Do not use cutoff discs for grinding; it dangerously weakens them.

 

On the other hand, small (22mm; 7/8”) diameter diamond coated discs (which are much slower cutting than resin bonded discs) excel at precise grinding. Once your coated disc loses the diamond grit from its narrow edge, keep it around for grinding excess material back to cut lines, or sharpening high-speed steel, tungsten carbide, and silicon carbide surfaces. Diamond coated cutoff discs good for sharpening drill bits and saw teeth; they are perfect for reshaping and reducing silicon carbide grinding wheels and stones.

 

[Mikey98118]

Cutting parts to length is most easily done with an abrasive disc mounted in a cutoff saw (AKA chop saw); the cheapest are about $140. On the other hand, surface cutting parts to length with a rotary tool or die grinder requires a proper cut line; this can be provided with an ink marker and sheet of paper rolled around the tube or pipe, instead of a pipe wrap. Then proceed to make the cut in the manner recommended in the Surface Cutting section below.

    Or, you can mark perfect cross lines, at true right angles, with a cheap little pipe cutter; it can also be used to completely sever the parts. But for parting, you will need a quality tool; it will cost double the price of the cheapest tool, but with reasonable care, will do the job for years, without breaking (don’t attempt to cut deeply with each pass; take your time).

    Separating parts this way will bend the inside diameter in the immediate area of the cut line several thousandths of an inch smaller; this can be quite handy with oversize choke sleeves, and some spacer rings. Otherwise, the inside of the part area might need to be ground or sanded to restore the original inside diameter.

 

RIDGID - CC247 RIDGID 40617 Model 101 Close Quarters Tubing Cutter (1/4” to 1-1/8”); $21.28 through Amazon.com is recommended for parting burner tubes.

[Mikey98118]

Rotary saw blades: Circular saw blades were once considered to be a grim necessity for wood, plastic, and aluminum cutting; their teeth multiply the likelihood, strength, and hazards of kickback. There are much safer tungsten carbide incrusted specialty cutoff discs available nowadays. Dremel’s EZ544 carbide coated cutoff disc is set up for use on their EZ402 Mandrel, which greatly decreases the possibility of kickback.

    If you insist on using teethed saw blades in a rotary tool, be sure to protect yourself with a Gyros safety guard. How about use in an electric die grinder? Just don’t go there at all! DO-NOT-DO-IT!

 

[Mikey98118]

Exhaust size and shape: One thing backyard casters and blacksmiths both worry over is how large to make the exhaust openings on their equipment. Too small and you have high back pressure killing burner performance; too large and you can't get enough heat to stay in the equipment to do your work. Of course, the closer to the "right" opening size your equipment is the stronger the forge or furnace can be built. Just don't get suckered into confusing the right size for a “perfect” size. As long as burner output can by varied (turn-down range), there can't be any such thing as a perfect opening size. The right size is what is needed to accommodate the burner's highest output (the highest you are willing to take it to).

    Variable is the optimal opening size; all other dimensions can be outright wrong, but seldom just right, with a burner flame that can be varied. This is one of the many reasons for controlling exhaust flow with an external baffle wall beyond a larger than needed ringed opening; thus, allowing the least heat loss through radiation, while maintaining optimal back pressure in the forge. Why include a ring around the exhaust opening? To divert hot exhaust gasses away from the metal shell, where it would otherwise overheat the metal.

    If you choose a simple brick baffle wall in front of the forge, keep the bricks at a small distance from the exhaust opening, to allow hot gases to move up and out, between forge shell and brick wall, while bouncing radiation off of a re-emissive (heat reflective) coating, and back into your forge. Keep the stock entrance only as large as is needed to move parts through.

    This arrangement helps to slow the flow of expended gas in the forge interior, as it heads toward the exhaust opening; and then speeds the gas up through the opening; another highly desirable trade off. So, you are gaining hang time for the heated gas in the forge, and recuperative savings from bounce back of radiant energy; another win-win situation. A baffle wall also minimizes infrared and white light from impacting your eyes and skin, improving your health and comfort.

Doors: Maximum clearance can also be provided with a hinged and latched forge door that contains built-in changeable baffle plates (high alumina kiln shelves are perfect for this). A door makes building the refractory structures of equipment much easier, and permits larger pieces to be heated then would pass through a narrowed opening. Best of all it allows movable internal baffles to be used, which would not pass a narrowed exhaust opening very wll; this promotes the use of single burners for small pieces, saving money in any cylinder or box forge run by two or more burners.

The door is a big step up from an exterior brick baffle wall; it should include a parts entrance that can be varied in size; for instance, with several round (or hexagonal) kiln shelves with different openings cut into them (for passing stock through), which can be exchanged, and held in a pocket on the door. All of these improvements don’t need to be seen to at once, so long as a hinged and latched door is included in the forge shell.

    While hinged and latched doors can do just as much on box shaped forges, all the examples I have seen slide up and down.

High alumina kiln shelves are seven times more insulating than hard fire brick; they are also tougher at forge temperatures, which is an important consideration for something you will end up shoving parts back and forth through. Using alternate kiln shelves, with different part openings drilled and cut into them is fine, but building an elaborate system of moving kiln shelf parts to ape the ability of bricks to change their openings comes under the heading of "gilding the Lilly." The additional energy savings it provides probably isn't worth the effort. Make up new openings in shelve baffle walls sparingly. Diamond coated and carbide coated rotary burrs (and diamond coated hole saws) are the preferred way to drill holes in kiln shelves. Friction cutoff blades and diamond coated blades are the best way to cut lines between those holes.

    You want to coat the hot-face of the door with one of the re-emissive coatings, use a formula of 95% zirconia silicate (zircon) and 5% Veegum (or bentonite as an alternate); this mixture makes a tough re-emissive coating for wear surfaces. Zirconium silicate can also be mixed with fumed silica to make a tuff and effective coating on refractories (but not on ceramic fiber products). There are other choices, Like Plistix 900F, but none of them are as economical or easily purchased in other countries.

    All these advantages can be applied in casting furnace mode, if a round kiln shelf is placed in a hoop, which can be swung into position above the furnace and swung out of the way during crucible removal. A mall center hole in the shelf allows observation and metal to be added to the melt; it also provides a rest for preheating metal to make sure it is thoroughly dry before placement in the crucible.

[jcornell20878]

Mikey98118

 

You said:   I’m not sure it is the same formula today. But. you can make a better formula, for less money than this product now costs. 100% colloidal zirconium flour can be purchased from various labs and mixed with phosphoric acid to make a high-emissive coating rated above 90% “reflective” of radiant heat"

Where can one find colloidal zirconium flour, and what are you using as your phosphoric acid source?

 

[Irondragon Forge ClayWorks]

That would depend on where in the world you are located.

[Mikey98118]

Did you look for the Zirconium flour on the web?

You should be able to buy phosphoric acid down at your local grocery store.

[Mikey98118]

Sealing and high-emissive coatings for ceramic fibers and other inner surfaces

Rigidized ceramic fiber products still need to be sealed for safety. Furthermore, the various coatings used for sealing tend to create a tough surface layer that holds high-emissive coatings from peeling away from the fiber’s surface; an irritating tendency that results from spreading high-emissive coatings directly on fiber products (those that aren’t rigidized first). Just as not all sealants are rated as high-emissive, not all high-emissive coatings are effective sealants, so we need to review the better-known products:

ITC-100 is strictly a high-emissive coating; Twenty years ago, I found that deliberately separating it by adding more water caused the non-colloidal particles to separate out, refining the coating, and greatly increasing its emission of radiant energy.

    I’m not sure it is the same formula today. But. you can make a better formula, for less money than this product now costs. 100% colloidal zirconium flour can be purchased from various online sources, and mixed with phosphoric acid from your supermarket, to make a high-emissive coating rated above 90% “reflective” of radiant heat.

 

Zircopax ( AKA Zirconium silicate): Some hobbyists concoct a tough sealant coating that is also a high-emissive product; they purchase zirconium silicate flour from a pottery supplies store, and mix it down with clay powder.  Zirconium silicate, while very tough is only rated at about 70% heat reflection, but I think this figure is misleading; since the other part of its structure is clear natural crystal, which will pass light rays with very little interference, and since its operating mechanism is re-radiance, I believe its overall performance in thicker layers will prove to be considerably higher than 70%; it is also very resistant to borax, and is an economical choice.

   Others use a slurry of Zircopax mixed into to colloidal silica and a little water; the same mix is used for shell casting; mix about the consistency of latex paint,  in a clear lidded jar. The Zircopax will settle out, once you stop stirring every few minutes, and cake onto bottom of the jar, with the silica and water remaining in solution over it; until it is broken up with a butter knife, and thoroughly remixed back into solution.

 

Plistix 900 is rated at 70% heat reflection, and makes a tough smooth sealing coat rated for use at 3400°F.

Matrikote 90 AC Ceramic Coating (one of the product line from Allied Minerals) is a very tough hard coating containing 90.4% alumina, 1.5 silicon dioxide as a vitreous(glass-like) binder, and 2.7 % phosphorus oxide as a polymerizing binder. Matrikote is good to 3000 °F, and would prove especially useful as an inner layer between outer coatings of higher use temperatures and rigidized ceramic fiber products.

 

Satanite is probably the best-known refractory mortar for use as a hard coating/sealant over ceramic fiber board; it is use rated at 3200 F, and is easily purchased in small quantities through knife making suppliers.

 

 

[CamCarpenter]

Hi, IFI,

I am coming here to Forges 101 to share a few photos that I've drawn up on Blender and get some feedback/input on my forge design. I apologize if this is not the right place.

The concept of my design is based around fire bricks, because I have those. I bought a whole bunch of Kijiji to make an aluminum smeltery, but as I went to fire up my crucible, I realized I would need to have tongs to remove it. The simple answer, of course, was to buy tongs, but it REALLY appealed to me to make my own. That led me down this rabbit hole of forge design...

I have done so much reading and watching on the subject of forge design that I may have gotten sick of it. I saw circles, made out of propane tanks and drums, I have read about oval forges, I have seen long and flat rectangular forges, and I have seen fairly square forges. I have seen forges using INCHES of castable refractory, and some that only use a 1/8th layer of castable refractory on top of 3 inches of kaowool. I have seen firebrick only forges and one that was just a few regular bricks placed around some charcoal with a hairdryer blowing into it. With that said, I have come up with a design that is more advanced than some I have seen, and definitely less sophisticated (and therefore cheaper) than others.

I hope the colours of my render help with understanding. The core concept was a hexagon for 2 reasons: one, I like hexagons. I think they are the perfect shape. Is that vanity? Probably, but it factors in. I like the look of a hexagon. Two, I tried an octagon, but unless I'm cutting the length of my bricks down, the inside of the forge was too big.

I am just realizing that I have to cut every brick anyway, (to make my 60° angles for my hexagon) so I could make it octagonal with a similar inside area. (oops) I also have been trying to get this done quickly, as I want to spend more time blacksmithing than designing my forge. I do understand I should not rush through this process, but I also don't want to spend unreasonable amounts of time redesigning and redesigning this forge. (I already made two designs for the smeltery, which I will be tearing down to make the forge) I want to get forging.

Back to my current design: It is a hexagon of firebricks 2 bricks long and 12 bricks around the face. (2 / side and 6 sides) I currently have them going lengthways to the back in my render, but I may choose to bevel the short ends instead when I actually build it. I imagine it will be easier to cut the short end than the long one. The bricks are 4 7/16" x 8 7/8" x 1 7/8" so that's what my forge is based off of.

The firebricks will be held in place with 1 1/4" angle iron, since I have access to hundreds of linear feet of it. My dad has been collecting bedframes for years as he helped people move, and he has said I can use his angle iron to make anything I want. I just have a basic approach: hexagonal shape on the front and back, then a few flat pieces to support the middle, then some lengthwise pieces to tie those three hexagons together. I have not designed a mount for my ribbon burner yet, that is why it just sticks out of the top of the forge. I have some high-heat spray paint to reduce rusting of the bed frame components once I'm done.

Inside, I went with 1" of kaowool because that was the cheapest kaowool on Amazon. But I've read on here that 2" is what is recommended, so I have mocked up a second render which has 2 layers of 1" kaowool.

On the kaowool, I plan to lay around a quarter inch of refractory cement. I have some Rutland 2200f castable refractory that I was going to use for the lid of my smeltery and just did not. I plan to use a firebrick, or a half of a firebrick as a forge bed, in case I decide to do forge welding in the future, as I have read that Borax is extremely harsh on silicates like castable refractory and especially kaowool. (though I plan to have no kaowool exposed when I'm finished)

For a burner, I am currently designing a system around a home-made ribbon burner. I have it designed out of 4" square tube steel, following John of Old Hickory Forge's design (

)

I did some math on the burner and found that 25 5/16" crayons (which is what I will be using, per John's design) has a circular area of 1.5625" square. I currently have 1 3/4" allocated for air/gas inlet, so I will be choking down by 1/2" square, which I suspect will have little to no effect, since my design has even more holes than John's does and he says it works great. I have included all other elements, including the baffle inside the steel tube. The ribbon burner will project about 1/2" on a 10° angle into the forge and be cast in place.

I am currently designing the air/fuel delivery pipe line, though I have watched a few videos on how to do so and have a basic idea. I am planning on using 1 3/4 piping (or 2", if that size is not available/more expensive) and my dad has a furnace blower from a house upgrade that he has given me to use. I will control the air/gas mix with a needle valve or a standard ball valve and a mig tip inserted into the gas line in the air pipe (I will try to find that link later, I have to wrap up this post before 5pm) I am planning on having all the necessary safety features that I do not necessarily remember right now including a pressure gauge on the propane tank and having it a minimum of 6" from the forge. I have heard 25' but that seems excessive, and my garage is only 20 feet long lol

I do not plan to forge in the garage for now, but if I start doing more blacksmithing than woodworking, I may bring the forge into the garage to reduce noise (so I don't drive my neighbors crazy, I've only been here a year mid-June lol) for now, I plan to wheel my forge out to the driveway and do my heating there. I am not sure where I will be doing my hammering, probably just bring it in the garage for that. I keep it well enough swept up that it shouldn't be a fire hazard. And I will have a garden hose near-to-hand the whole time.

Well that's all the time I have for this post! If you have any insights or constructive criticism, I am always ready to hear it! I do not think I know everything (definitely not) though I have read a lot on the subject, I am ready to cede academic knowledge for practical, as I have zero of that.

Thank you in advance, IFI community for your insightful and helpful correspondence!

(I included the blender file, in case anyone wanted to take a look at it or give suggestions. I don't mean to be presumptuous, rather the opposite, let you all see right into my process!)

Hexagonal Forge V.1.3.blend

[Irondragon Forge ClayWorks]

Not planning to run the propane forge in the garage is very wise. A propane forge produces copious amounts of CO (carbon monoxide), more than an automobile. If the garage is attached to the house it is especially important to prevent CO infiltration into the house as CO will kill in short order. Even with good ventilation in a stand alone garage it is imperative to have several CO detector alarms installed.

https://www.iforgeiron.com/topic/62131-co-is-a-killer-but-co2-is-as-well/

Reviewing this section is recommended for beginners and experienced smith's as well. Here at IFI we stress safety to the nth-degree.

https://www.iforgeiron.com/forum/28-safety-discussions/