Forges 101

[Mikey98118]

Jasent,

you thought quite right!

 

 

Andre

You might do well to investigate ceramic burner heads, like Giberson's; similar designs will provide you the most bang for your burner bucks; especially his new miniature head. Also, remember that the formula can be used as the perfect adhesive to glue pressed parts together with. Waxed wooden (or plastic) forms; these my first choice for pressing this refractory into homemade molds.

[Mikey98118]

Sorry; that should read "Andrew".

[Mikey98118]

Fire cement is low-priced and readily available in small cans; it is not normally used in place of regular refractory hot faces because it has it is not made to be used in thick layers and will crack and spall if used for a hot-face. Tim Gunn seems to have solved that problem, by watering down the cement so that it can deeply penetrate ceramic wool blanket; so the cement helps strengthen the blanket, and vice-versa. Fire cement comes ins more than one temperature ratings; use the highest one available.

One of the three kinds of commercial rigidizers works the same way, so there is plenty of precedent for this process. I would recommend spritzing colloidal silica (fumed silica in water) on the blanket and firing it first, to strengthen the blanket, and then applying the watered down cement to seal and toughen the blanket. 

[timgunn1962]

To be fair, Mike, "solved that problem" is over-egging it a bit. 

I get the strong impression that most beginning smiths want to build the ultimate forge straight off, thinking that it'll allow them to do everything immediately. 

The reality is, of course, rather different.

I'm in the UK where we don't have the Wayne Coes of this world selling small quantities of high-performance refractories at prices most hobbyists can justify to themselves or their significant other. If I want 1400 degC/2600 degF blanket, I have to buy a full roll. If I want Kast-O-Lite 30LI, I have to buy a 55 lb bag.

The "cheap fire cement and a double wrap of blanket" approach is just the cheapest, easiest way I have been able to come up with that allows a beginner to get started with forging over here. It approaches the cheapness of the truly abysmal sand-and-plaster-of-Paris constructions seen on youtube, whilst actually working quite effectively (given an appropriate burner) and lasting beyond the second or third use (given reasonable care). Body-Soluble fibre blanket is available by the metre from ebay dot co dot uk and fire cement is available at every DIY store.

 

I've played about with forges a bit and built versions that range from distinctly meh to pretty good (at specific things), though they have all been aimed primarily at various aspects of knifemaking.  

I've played with various other things too, including home-brew rigidizers using both fumed-Silica-in-water and Sodium Silicate solutions. I've tried porcelain clay-and-Zirconium Silicate surface coatings, IFB forges, modified-torch burners, a couple of homebuilt burner "designs", burners built around commercial Venturi mixers and electric Heat-Treat ovens. Results have been mixed, but interesting. I'm not good at write-ups and the few I have done have disappeared along with the British Blades forum. If I can dig out some of my notes and pictures, I'll try to get some of the more useful stuff on here over the next few weeks.

 

 

 

 

 

[Mikey98118]

GOOD!!!   You may only consider it as an economical way to toughen ceramic blanket insulation within a forge, but when one of the IFI guys posted a photo of a section ceramic blanket being used as an external exhaust cowling, he unknowingly started a new direction in forge construction; multiplying the usefulness of your technique. I would still like you to post it on this thread; otherwise, you're likely to get asked to discuss it over and over in the coming months 

[genesaika]

I have a question. You said that a box forge should be taller than it is wide to allow the fire to properly combust and not hit the material you are working. Instead of making it physically tall could you make the burner ports taller? 

[81pistolsfiring]

On 9/3/2017 at 1:54 PM, Frosty said:

 

I did some research on read on Wikipedia that bentonite is mixed with sand to withstand tempatures reaching the molten metal stage of heating. 

So is sand needed in a kitty litter jar mixture as well? Haven't researched all the ingredients of kitty litter as of yet. 

[Frosty]

Bentonite clay mixed to thick toothpaste consistency is used to plug the tap in cupola melters. A big gob is put on a round board screwed to the end of a broom or shovel handle,. When they're done drawing iron the gob of bentonite is shoved into the tap hole and held in place for a few seconds. The 2,600f iron and the flame from the burner belt dries then fires it in place where it holds back several hundred lbs of molten iron. That's in the small cupola Pat demos with at various iron pours here.

I'll have to ask him if he uses sand in the plug mix. I'll try to remember next time I see him.

Frosty The Lucky.

[Mikey98118]

81pistolsfiring  and Frosty

Bentonite clay as a refractory or kiln wash is a worthwhile subject to investigate.

As to cracking in thermally resistant zirconia silicate tile; it should be more easily avoided in the first place, and repairable if it happens. Consider how small shrinkage cracks are as compared to to the original area of the tile; doesn't that simply invite using the refractory as glue for self repair?

 

genesaika

I did say that a box forge should be taller than it is wide to allow the fire to properly combust and avoid impinging on the material being heated. Yes, you could make the burner ports taller, but it is not recommended. You could also change out your burners for a ribbon burner, to make the flames much shorter. I intended the original comment as a cautioning statement; as the easiest repair is the one you can avoid. But for people who already have forges with horizontal dimensions too large to be adequately heated by burners with short enough flames. The easiest answer is to change out its burners for smaller ones with shorter flames. By adding more ports, instead of lengthening them, four smaller burners can also do the heating of two larger burners.

Note: If you start with two burners positioned fore and aft, the third and fourth burners should be position left and right. But, if you start with two burners positioned left and right, try to position the third and fourth burners left and right too.

 

 

genesaika

Your advice to builders to generally loosen up when building their first forge is best followed before construction; it is s;dp likely to be even more needed after construction.

 

 

[Mikey98118]

Here is a steady source of minor amounts of ceramic blanket and board at sane prices

http://www.mcgillswarehouse.com/fiber-board-paper-blanket

[Mikey98118]

Jay Hayes; forgotten genius of forge design

Well, not really forgotten, but certainly obscure. Jay is a heating engineer and one of the earliest of movers and shapers in homemade gas forges. His oval forges have been around for decades; he is also an early innovator of burners, brick, and "D" forges. I consistently consulted him while righting the section on propane hoses in my book; he would have become famous if he had leaned into keeping up a modern website (it remains unfinished after all these years). Unfortunately, you must do a Google search, to find out more about his work, but it is well worthwhile: https://www.google.com/search?newwindow=1&source=hp&q=jay+hayes+forge&oq=Jay+Hayes+for&gs_l=psy-ab.1.0.0l2j0i22i30k1.6532.28773.0.33616.14.13.0.0.0.0.227.1311.9j3j1.13.0.dummy_maps_web_fallback...0...1.1.64.psy-ab..1.13.1304.0..46j35i39k1j0i131k1j0i20i264k1j0i20i264i46k1j46i20i264k1j0i46k1.0.Wz_P5FOSjnU

 

[Glenn]

This is a reference post (related) that you may want to read.  ---> Click Here oliver-upwind-burner

[Mikey98118]

Thank you for posting this on this thread, Glenn. It is a very important example of how far people can go with their own designs.

[Mikey98118]

Glenn,

Please delete my nickname from this thread; you could leave that area blank, or replace it with something like IFI et al. It is time for the innovative forge designers, to feel encouraged to post them here; they need to feel this is their thread, because it is

[Mikey98118]

"I made a small production of burners and like our children, there are not 2 of them identical.It would take a lot of file work to fine-tune them all similar to one another, but I do not think that the result is worth the work."

Only to perfectionists; it would make no difference in a forge.

[Thidwick]

The guidance says that the burner should be used to dry and cure the rigidizer after its applied to the ceramic blanket. Would a heat gun be sufficient to dry it before troweling on the refractory cement?

Quote

but them there ceramic fibers are made of alumina and silica; this difference is aided and abetted by the fact that the micro thin layer of silica powder that remains behind when the water dries out away are tiny, which makes them much easier to PARTIALLY melt. 

 I presume the forge will get hot enough to "melt" the silica even after kast-o-lite (or whatever) is added and cured, yes?

[Jasent]

It's much easier to apply the refactory after the rididizer is cured. My heat gun gets up to around 800f. I don't think that's hot enough to melt the silica. 

Why not use the burner?

[Thidwick]

The advice was to keep the burner moving back and forth over the wet blanket , but it's going to be a tough fit in there with a flaming burner. Maybe I misinterpreted the directions.

 

[Jasent]

I'm no pro but I can tell you what worked for me. After I sprayed the last layer I let it sit for a hour or so. Then took my burner and held it just in side the front of the forge and moved the flame over the whole inside till it started steaming. Then left it alone for a few min. Then I put the burner in its hole and fired it up. At first the steam keeps putting it out. Every time it did I let it breath a few min then lit it up again till the steam stopped putting out the flame. Then I let it come up forging temps for min or so then shut it down and let it cool 

 

[Mikey98118]

20 hours ago, Jasent said:

I'm no pro but I can tell you what worked for me.

What an excellent attitude! Then you followed up with your personal experience; this is better than "advice from the pros." This is the best kind of input for confidence building in beginners, and that is what beginners need MOST!

[Mikey98118]

Burner position update

For eighteen years I've recommended that burners be positioned vertically down (and at a tangent in tunnel, oval, and "D" forges); this allows the flame to impinge on high alumina kiln shelf or high alumina refractory floors, producing the most durable position in energy efficient forge designs.

But circumstances alter cases. Better insulating and reflecting materials have recently become available at moderate prices. So, it is time to turn away from the vertical down position; this will eliminate overheating burners from chimney effects, which is an important safety factor. There are many other advantages to being free to choose the most efficient angle to aim your forge burners; especially in brick forges.

[JoeThePro]

Can someone advise if kaowool superwool plus (1832°F continuous, 2192° F classification rating) rigidified and covered with kastolite will hold up, or do I need to spend the extra for kaowool superwool HT (2102° F continuous, 2372°F classification rating)?  I've found a good local deal on the 1", 8 pound kaowool superwool plus.  They only have the HT in 2" thickness and I'd rather do multiple layers.

[Jasent]

If you read threw this thread there is info on getting correct wool for free or very cheap.  Hvac company's can not use scraps and they get thrown away

[Mikey98118]

Or if you have a good deal on the lower rated product, You might as well go ahead, becuase by the time you need to replace the ceramics there will be better choices for low prices replacing all this stuff.

[Mikey98118]

 

Rigidizers

There are three kinds of "rigidizers" at present: Colloidal silica; colloidal alumina; and fine alumina powder with a binder. The first two kinds of rigidizers diffuse onto the threads, which ceramic wool is made from, by capillary attraction; but the alumina product is use rated higher than silica. The third kind acts similar to Christmas tree flocking. I don't think it is likely to do any better than watered down alumina cement, which is what I would use instead if that was the effect I was after.