Forges 101

[VainEnd84]

Look up, industrial refractory suppliers near you, not all of them are willing to sell small volume. My biggest problem originally was finding individual bricks locally for less than $13-$15 each at pottery suppliers an the like which is terrible. Then I started looking in other places and eventually I was talking with a guy who makes pizza ovens who put me onto the company he buys fire bricks from. I can buy a case of 12 for $60 as long as I pay cash and go directly to them. Ebay and amazon are the other option.

[Another FrankenBurner]

I would be very happy if I could find a case for $60.  I am currently going the pottery supplier route and paying almost $9 a brick.  Amazon doesn't seem to have much, or I am missing them and ebay is where the shipping prices are sometimes $11 for a $6 brick.  I'll keep looking, thank you.

[VainEnd84]

Another thought is if there are any are colleges near you that have glass blowing, you can go and talk to them and ask who builds/maintains their furnaces, that might put you onto another rout. The stock on Amazon is spotty at best, you have to look regularly

[Mikey98118]

 I like Amazon; I really do. But it takes high volume sales numbers to get good prices on what they sell. Little guys try harder on eBay. So, I always look there before buying anywhere else. Amazon prices for any kind of firebrick is way to steep for me. On the other hand, Amazon has proved to be a good marketplace for air/fuel torches and hose adapter kits; both of which I purchased there this week.

On ‎12‎/‎19‎/‎2018 at 11:10 PM, VainEnd84 said:

There are 4 other types of commonly available fire bricks, k23, k28, hard fire bricks, and medium duty fire bricks (in talking with some suppliers I have learned that new manufacturing techniques and materials are resulting in stronger and better insulating bricks to be available in the next few years). We can toss out the medium duty fire bricks for use in forges because they generally have a max load of 1800-2000 degrees F and are meant for things like fire places. We can likewise toss out using k23 fire bricks as a max thermal load of 2300 F and a sustained load of 2100 F they will start to thermally decay much too soon. And hard fire bricks have almost no insulating capacity so there is little point in using them either.

You've brought up some very good points, but I'm not suggesting just any old 2600 F rated firebricks. K2600 bricks, manufactured by Morgan, can match the insulating ability of ceramic fiber board and blanket at forge temperatures of 2000 F and up. There are loads of castable refractories rated at 2600 degrees. Many firebricks are just molded blocks of castable refractory. Morgan's K series bricks are specially treated with live steam during production to create air holes, much as the old style crumbly 2300 clay based insulating bricks have a foaming agent added to create air holes. Only Morgan's K series bricks are far tougher than the foamed clay bricks.

The one thing your very valuable information doesn't address is the opportunity in insulating bricks brought about with the temperature gradient between their hot-face and cold-face sides. Below 2000 F, K2600 brick falls behind the insulating ability of ceramic fiber. But the most exciting thing that is available from this brick, is that it is a tough high temperature rated product with good enough insulating abilities to protect the fiber insulation from the thermal loading that comes from their hot-face side. The better able your forge floor is to insulate the ceramic fiber beneath it the longer it will last. Their advantages don't end there, K series bricks are quite porous, so their surfaces are perfect for coating with high alumina cast refractories, or the homemade refractory formulas that some of the guys are playing around with. Their advantages don't end there, K series bricks are quite porous, so their surfaces are perfect for coating with high alumina cast refractories, or the homemade refractory formulas that some of the guys are playing around with.

 You see, I didn't start out looking for bricks to use in box or brick pile forges, but as a mediation layer between flame impingement surfaces on forge floors, and the ceramic fiber insulation beneath them. Using it for brick forges simply is to good an opportunity to ignore.

I suspect that these bricks are only the first of a long line of superior firebricks coming on the market in coming years, but a lot of us have waited a very long time for anything this good to show up at all

[VainEnd84]

2 hours ago, Mikey98118 said:

Morgan's K series bricks are far tougher than the foamed clay bricks.

The engineer I spoke to didn't get into specific manufacturers just general information, that is very interesting.

 

2 hours ago, Mikey98118 said:

I suspect that these bricks are only the first of a long line of superior firebricks coming on the market in coming years, but a lot of us have waited a very long time for anything this good to show up at all

One of the things he talked about is the field of high temperature insulating plastics. The way he described it is like two part expanding spray insulation, but that can handle 3000F and doesn't suffer from thermal cycling. Apparently there are many high temperature plastics out there but we didnt get into them as he said they don't really apply to building forges and kilns etc.

[Mikey98118]

14 hours ago, VainEnd84 said:

Apparently there are many high temperature plastics out there but we didnt get into them as he said they don't really apply to building forges and kilns etc.

In recent years I have averaged three times as many hours investigating new products as inventing or writing. There are marvelous things out there; finding them with reasonable prices and/or availability is what separates the men from the boys. Did you know that carbonized toast is one of the best refractory insulation around? Alas, it simply is't practical.

[Mikey98118]

Chimney effects don't quit damaging burners just because we're not paying attention!

I wrote the following in reply to a reader whose burner hose over heated so badly it had to be replaced:

"As to the burner heating up and scorching the hose; I see no choke plate on top of the burner. When you turn the gas off at shut down is your burner becoming a chimney for super heated forge atmosphere to to run back up, overheating your hose?"

Linear burners with gas pipes that run across the inside of a reducer used to be ubiquitous, and they are still common today. What isn't common anymore is to see choke plates on these burners, which can be closed off completely after shut down. If your burner faces down into your forge it will become a chimney and overheat after it is shut off, unless it can be closed up completely. How much damage that does simply depends on how careless you are also being about plumbing the burner. Obviously copper tubing is going to hold up much better than propane hose.

But really, don't you think that a little more care could leave your equipment a lot safer?

[Mikey98118]

For those still building Ron Riel type burners, with gas cross pipes, Larry Zoeller Forge still sells choke plates for them.

Choke plate for the Modified Side Arm Burner, 2 1/4" diameter x 14 gauge
$1.50 each plus shipping.

[D.Rotblatt]

Posted this on a different thread, and Mikey suggested that I transfer the information to this thread.  In a nutshell we discuss a different coating for ceramic fiber liner using Zircon and a Colloidal silica thats used in making shell molds (the brand I happen to have is Adbond II from Remet).  The result is a reflective (or emissive) eggshell thick Zircon layer bonded to the ceramic fiber.

          ----------

I've been building forges and furnaces since the 1980's.  Here's one I designed and posted several decades ago: http://www.rotblattsculpture.com/Articles/buildingabronzec.html.  I've been using Reil burners and built Mikey burners as well.  Now I thought I'd build a ribbon burner (or multi burner?) with a gun type delivery.  I'll post some pics later.  Anywho....I've been reading on how you line forges.  I've done mine different.  In the old days, I just used ceramic wool.  When the dangers of the fibers and the wonders of the ITC stuff got publicized, I started to coat the fiber with a straight Zircon and Colloidal silica for shell casting.  This was back around 10 years ago and I was teaching Art Foundry Casting at Cal State University Long Beach and got a sample of Zircon from Remet (a foundry supplier).  It formed a good paper thin coating on the ceramic fiber.   Heated up instantly, and stabilized the wool. 

18 hours ago, Mikey98118 said:

The Zircon (zirconium silicate) and silica coating for ceramic fiber blanket sounds interesting; it should be easier to deal with than Zircon and bentonite, although not good for as high a temperature. Do you use fumed silica and mix the two as dry powders, and then add water? What proportions or thickness do you aim for? Any preferred technique for application? Can you just heat cure it in a few minutes? Inquiring minds will want to know the specifics.

I looked at your article; it reminded me of the online casting groups that are long gone; a pity that. Welcome to the group. Does the "D" stand for Dave or Dan?

You mentioned that a 1/2" thick layer of castable refractory constitutes a massive heat sink; compared with a thin coating of zircon it does. But how much of a heat sink depends on the refractory, and good or bad can be a point of fact, or just a point of view. Some people consider the armoring effect of a cast refractory layer to be important; others feel reasonable care should make it unnecessary. I'm part of that second group, but worked around gorillas for so many decades that I know my preferences are not practical for most. 

I used to do a lot of shell mold casting.  The colloidal silica is the binder that is used for building the layers.  In shell casting, silica flour is mixed with the colloidal silica.  The mold is dipped in the slurry then sprinkled with crushed silica - first layers with fine, then medium, then course.  If you are casting iron, steel or a higher temperature material then bronze (I did bronze), then you use zircon flour instead of silica flour so it will take the heat.  The colloidal silica is a premix that comes in 5 gallon containers.  It looks like a milky water, a little thicker than water (could just be fumed silica in water, but I have no idea).  The type I use is called Adbond II, and I got it from Remet.  What I used to do is dab it onto wet ceramic wool with a disposable brush then just heat cure (never had the patience to just let it dry).  Thickness and feel is like an eggshell (just not so smooth).  One or two layers was all I use, basically to bind the outer layers so I won't be breathing in ceramic wool particles and I thought it would reflect (though now I find it's emitive...which I just found out by reading on this forum, thank you very much!).  I figured since it was reflecting, a thin layer was all I needed.  Seemed to work well, surface got brighter, wool was stabilized, formed a hard eggshell layer.  

I value a forge that heats up quick, and cools down quick.  The only advantage I see of a slow cooling forge is for annealing, but if I want to do that I have an oven.  A thicker heat sink liner is stronger so it holds up to more abuse, but will take a longer time to get to heat (thus use more gas).  I imagine it would also act as a storage for the heat, so if a cool piece of metal is put against it it would transfer some of it's energy to the metal (but that's an argument for a denser floor rather than a dense layer of liner).  The way I used to explain the advantages and disadvantages of ceramic wool vs a cast liner for furnaces is that if you are doing only one pour at a time, ceramic fiber is more efficient since it heats up quickly, but if you are doing a number of pours in a row, a cast liner is better as it holds the heat and you don't have to heat it up as much.  As you say, it's really just a matter of opinion.

But I think I'm starting to babble....I'll leave it at that for now.

-Dan

[D.Rotblatt]

1 hour ago, D.Rotblatt said:

The Zircon (zirconium silicate) and silica coating for ceramic fiber blanket sounds interesting; it should be easier to deal with than Zircon and bentonite, although not good for as high a temperature.

Mikey.  You mentioned that the Zircon/Colloidal silica mix would not be as good at high temp as the Zircon/bentonite mix.  This made me curious, so I researched it a bit.  From what I can find, the colloidal silica binder is Silica Dioxide in suspension with other stuff.  Silica Dioxide has a melting point upwards of 3100 degrees F.  Bentonite melts at around 2200 degrees F.  Seems to me that the colloidal silica binder would hold up better at high temps.  It's made to bind a ceramic shell for casting steel and high temp alloys.

A thought: Fumed silica is also Silica Dioxide.  Since Colloidal Silica binder is expensive and only sold in 5 Gal minimum, I'll try using some fused silica and water as the binder for Zircon and see how that compares to the binder I have.

-Dan

[Mikey98118]

IT is likely that fumed silica is what they are using for binder. Whether materials science is a fascinating or treacherous study is probably a matter of spleen. One thing it sure doesn't seem to be is straight forward

Veegum T is the binding/ elasticizing agnt of choice, and bentonite is simply a handy alternative for most folks. But I think what the central issue is likely to come down to is the amount of binder needed. 3.5 % is recommended to make a solid ceramic for tiles, crucibles, flame retention nozzles, etc. 5% of the binder is recommended to make a re-emissive and seal coating. I estimated once that the ceramic would be good to about 4300 F.

Note that I'm not interested in winning a debate. Your idea is fine and dandy at 3000 F and far easier to execute. Even if I'm right with the 4300 F estimate, this ceramic has proved difficult to make into usable items. Your way should be easy for people to use; it wins the blue ribbon for practicality, Because 3000 F is more than sufficient in most cases.  The two formulas have zircon's wonderful utility in common, but all similarity ends there. That's ceramics for you

So, if I believe these words, why bother dealing with the hard to handle formula at all? Some of us like to "push the envelope." With a background in casting you can appreciate that crucibles lose strength when they are close to their rated temperature; The same is true of flame retention nozzles.

A guy who built one of my first burner designs, semi-melted their nozzles in his forge. He was thrilled with the heat. I was horrified with the damage; it left lasting impressions on both of us! Polypropylene gas will burn so much hotter than propane that it turns the nozzles on my burners lemon yellow out in the open air; that's without even adding oxygen enrichment from an oxygen separator. What is needed for a practical forge burner is a lot less than what is needed for an all around hand torch; A torch that isn't joined at the hip to oxygen cylinders. There is so much that artists can do with heated metal, but the cost of oxygen is one of the stumbling blocks that needs to be kicked out of the way first.

[Mikey98118]

Dan,

Many thanks for posting here, were lots of folks can read and follow your method of making a thin hot-face layer that will seal and reflect heat back into the forge from ceramic fiber insulation. And thank you for questioning my viewpoint; all my favorite people do. We need to question each other to keep the topic honest. But most of all, thanks for writing with a personal touch; it reassures folks to read that, and reassurance is a big help when someone's dealing with the worries that come during equipment construction.

[D.Rotblatt]

Mikey - I have no dog in this race!  I just want to find out what works, and what works for our situation - so I hope my questions/statement didn't come off combative. Just curious and hoping to rectify a lack of knowledge.  BTW: My 3000+ degree numbers are just a best guess based on melting points of the ingredients online - not any real world testing.  

Speaking of real world testing.  Since I was putting the face on my forge today so I thought I'd try some mixes of Fused Silica against Colloidal Silica binder on some scrap pieces of ceramic fiber. 

RIGIDIZING

The Fused Silica solution (FS) didn't soak into the fiber deeply, it stayed on the top unless the fiber was wet first.  Even then it tended to stay on the surface.  The Adbond II quickly soaked into the fiber quicker than water.  Unfortunately when heated to red heat the Adbond II soaked fiber shrunk, the surface where it got hot turned into a solid mass.  The FS formed the expected hardened layer on the surface.  Another piece of fiber with only the surface 1/8" wetted with the Adbond II did rigidize fairly well.  

In summation, the FS solution works much better as a rigidizer, Adbond II can work if applied carefully, but if you use too much it will destroy your ceramic fiber.  Adbond II is not recommended.

ZIRCON/FUSED SILICA VS ZIRCON/ADBOND II

A slurry of Zircon and Fused Silica was applied to a scrap of rigidized dampened ceramic fiber quickly dried in the dragons breath of the forge then put inside and brought up to red heat.  It seemed to for a nice layer bonded to the surface of the fiber.  I then added more Zircon to the slurry until it was the thickness of latex paint.  A thick coat was applied to the surface of the fiber to make a thick second coat. This was dried the same and heated to red heat.  The surface cracked (like mud) and flaked off when scraped gently.  

The same treatment was used for the Zircon/Adbond II mix. The second coat did not crack or come off.  This was expected, since that is exactly what it is designed for when making shell molds.  I even added a third coat ending up with maybe .030 or .040 thickness - like a thick egg shell.  It was surprisingly strong, but a good tap with an 1/8" rod broke it.  I have tested it in the past vs. flux and it is inert to flux...unless there is a crack. 

I went ahead and finished my forge with the FS for rigidizing, and the Zircon/Adbond II for the hardshell/emittive layer.  Working on rigidized ceramic fiber made it really easy to apply the Zircon solution.  I just painted it on.  Fired the forge for a few seconds at a time until dry, then brought up to red heat.  Let it cool (about 2-3 minutes), then applied another coat.  Took me about 1 hour to face the lining.  

This is a really fine hard shell for surfacing the ceramic fiber, but Adbond II or any ceramic shell binder is really sold only to industry - meaning the smallest amount I've seen is 5 gal.   I think I used a no more then a cup of Adbond II to do my forge (7.5" ID x 13" deep).  Remet has a division for artists, so someone who is interested may want to call and talk to them and see if they will sell small amounts. 

[Mikey98118]

Thanks, Dan.

That's all good stuff. One of the things we all enjoy here is exciting new ideas. And won of the things I personally enjoy is talking guys into the deep end of the pool. This time it will be you doing it, but it's still fun when it happens

[Frosty]

On 12/19/2018 at 8:44 PM, AnotherCurtis said:

I would be very happy if I could find a case for $60.  I am currently going the pottery supplier route and paying almost $9 a brick.  Amazon doesn't seem to have much, or I am missing them and ebay is where the shipping prices are sometimes $11 for a $6 brick.  I'll keep looking, thank you.

Call "Distribution International," they have a brick and mortar store in Spokane Wa. 

Frosty The Lucky.

[Another FrankenBurner]

I called them a couple days ago.  $4.98 a brick but shipping rates made it more expensive then my local $8.75 a brick.

They also said they were not K26 but some other brand of 2600 brick which they thought was the same.

Question for Frosty, do you have a corn cob pipe?

[Mikey98118]

Frosty,

Apparently you and I bought our K26 bricks just in time a few months back; their prices on eBay have doubled in some cases, and high shipping charges have been added in others. Some offers do both! This is what ticks me off about trying to squire materials; greed!

 

[D.Rotblatt]

Curtis, if you ever head down to Salt Lake city, there is a Harbison Walker location there.  Give them a call.

Salt Lake City, UT GSC
4521 West 1980 South
Suite 503
Salt Lake City, UT 84104-4719
xxxx-xxx-xxxx

[Frosty]

On 12/20/2018 at 4:25 AM, VainEnd84 said:

The engineer I spoke to didn't get into specific manufacturers just general information, that is very interesting.

I browsed into the HTI site looking for the information sheets on the Morgan K series bricks again. I remember what it was like now, really difficult to find the darned things so I stopped after a while. Morgan's K series thermal tiles are only called bricks when they are common brick dimensions, otherwise they call it thermal tile. 

What I rediscovered browsing was the K rating system used on fire brick and there's a significant difference. A brick rated K26 is as you describe but Morgan K series refractories is just a brand designation not the thermal rating. I thought I'd read the Morgan k 26 had a working max temp of 2,600 f. with a safety factor and it didn't begin degrading till it had spent time in or above it's safety factor range. This may be a mistake on Morgan's part naming a high performance product after a rating system that doesn't seem to apply. 

Unfortunately I can't just say that, I haven't been able to find the data sheets again and I can't trust my memory anymore. What I can say for sure from experience using the product is the old soft insulating firebrick coated with either ITC-100 or a home brew zirconia kiln wash only last 2 - 3 firings to welding temp before they've degraded past useful. I rarely get a second firing before a brick breaks. The Morgan K 26 I'm using are going on their second or maybe third year in tact. I don't fire a forge so often anymore and don't in winter at all but I've still brought those K 26 tiles to medium high yellow probably 40-50 times. 

Were it not for my experience I wouldn't question your engineer's opinion or general trade knowledge but the Morgan K series tiles are concrete hard at high yellow temp and haven't shown signs of degradation so far. (knocking on wood!) I really wish I were still good at rooting out info from obscurely indexed sources. Stupid TREE!

I didn't buy off Ebay Mike, D.I. has an outlet in Anchorage so I just dropped by and picked up a case. Under $4.00/ brick by the case. I might have to give them a call and see what the price is now. 

No pipe Curtis, not since the '70s when I was practicing better living through modified blood chemistry. Corn cob pipes don't last long, I actually bought a meerschaum that'd probably have a drug dog alerting from the road. What makes them desirable for tobacco makes them a terrible choice for. . . other.

And don't even ask,  nobody picks my carrot but me!

Frosty The Lucky.

[Mikey98118]

Maybe 1" K26 tiles backed by ceramic blanket is the way to go, money wise?

Merry Christmas to one and all 

[Mikey98118]

I find it interesting that both Veegum and fumed silica have small enough particles to be colloidal. I wonder if there is something to be gained in mixing the two as a binder/elasticizer, or of trying bentonite and fumed silica for the purpose?

[horse]

Ftrosty you make me laugh all the time. I had to read your Meerschaum pipe thing three times to figure out where you were going with that. My tobacco shop pile is corn cob. Yep just burned out the bottom. Loved that pipe. 

[Mikey98118]

Rigidizer isn't a safety item

Well, there was just a big hullaballoo about the dangers of ceramic wool fibers getting into the air, and then into our lungs. One guy brought up how wrong it was to claim that rigidizer will protect us from that; he is right to. I have seen a few guys bring that idea up, and it is bunk. Rigidizer helps lengthen the amount of time thermal cycling will take to break the fiber down; it can't stop it. As Latticinio stated, sealing it off is the only answer to this problem. Rigidizer's other chore is to stiffen the insulation, so that it makes a better support for thin seal coatings, and cradles for refractory shells; they are what we should depend on for protection from airborne particles of broken down insulation. 

[Mikey98118]

It starts when we are children, with our mothers or aunts saying "don't play with knives" or "don't run with scissors." Throughout life we are presented with reasonable advice on safety. Some people over react and try to avoid all danger by avoiding scissors and knives. Other people scoff at all advice and end up cut or stabbed.

I worked with steel for more than forty years, and saw fools die--and worse--several times. Unlike when I started out, there is rarely any lack of warnings for our protection; just a lack of attention paid to it. As to those who panic and run away; good. If they can't pay attention and follow safety procedures, it is better that they just leave.

For the scoffers; it is said, but if they don't win their Darwin awards one place they will just win them somewhere else.

[Mikey98118]

Zinc is not an automatic no-no

Using zinc coated sheet metal or parts (such as car mufflers) is okay if you're careful about doing it. The boiling temperature of zinc (the point at which it makes fumes) is 1670 F. Your forge shell should not get higher than one-third that temperature. But you do need to be careful to keep the shell away from the edge of the exhaust openings, by not making the openings in ceramic fiber, kiln shelf, or refractory even with the shell.