Insulation and refractory order

[alexscg]

Hi everyone, did a lot of reading on this forum, first post.

I am building a gas "forge" out of a 6 gal steel pail and decided to go with 2x 1" inswool insulation.  Now I am considering refractory layers and a rigidizer.  I have Satanite, Plistix 600F and ITC-100H.  The order I am thinking of going with is (starting from outside to inside): Steel wall, 1/8" satanite, 1" inswool, 1/8" ITC-100H, 1" inswool, 1/8" Plistix 600F.  "Buttering" each application.  Looking for advice on better order, replacement of materials, etc., and reasons why.

Also have a question on whether I should spray paint the inside of the steel walls (before applying anything) with heat resistant paint (Rust-Oleum 248903).  The reason I am thinking it would be a good idea is because I want to prevent any kind of rusting, especially given that the first application of satanite would bring water in contact with the steel surface.

I am planning to melt aluminum, brass, maybe silver and at most copper so I am not planning on having anything over 1100 C in the crucible.

Thanks in advance!

[MaxwellB]

Putting the ITC100 in between wool will be a waste. As would the satanite between the wool and the shell.

Check out the Forges 101 section. You'll be amazed at the amount of information collected here over the years. I'm still digging through most of it.

What your ideal order should be is Shell > 1" layer of inswool rigidized > 2nd 1" layer of inswool rigidized > Satanite (different people suggest different thicknesses, I'd say go with somewhere between 1/4" - 3/8") > Plistex OR ITC100. Both are IR reflectives, there's no need for both. I think ITC100 is rated higher, so if you already have that go for it.

I wouldn't worry about the inside of the shell. If you want to paint the outside, fine, but it'll be more for aesthetics than anything else.

[JHCC]

Welcome to IFI! If you haven't yet, please READ THIS FIRST!!!

[Frosty]

Welcome aboard Alex, glad to have you. If you'll put your general location in the header you might be surprised how many members live within visiting distance. 

Max laid out the proper order but I certainly would not spend the money for ITC 100,  it just isn't effective nor durable enough to justify the price. 

Frosty The Lucky.

[MaxwellB]

Yeah, I only mentioned it because he said he already had it. If it's a "what to purchase" thing, then it's plistix. 

[alexscg]

Thank you Maxwell and Frosty!

Reading through Forges 101 I remembered that I've neglected to ask about the rigidizer.  Seems like colloidal silica and water (and food coloring) will do the trick.  From what I am reading the method is generous spot application with a spray and spot hardening with a torch, working your way all around.  Do the first layer then do the second layer in the same fashion.  What is the right ration of silica to water for this type of application?

Also I read that ITC-100 is more of an IR absorb-and-release kind of a thing and becomes diamond-hard after curing, and Plistix is more of an IR reflector.  Wouldn't it be better put a coat of Plastix on top of rigidized inswool and then a 1/4" layer of ITC-100 ?  This would sort of trap the heat in the ITC-100 layer and allow it to get hotter quicker.

Silly thought, if I won't have enough of ITC-100 to coat everything, would mixing it with Satanite be a good/bad idea?  I am not certain of the exact composition for both so don't know if they will play nice together at all temperatures.

Another question on flooring.  I already have some firebricks (the common Rutland 1-1/4")... If I glaze a firebrick with borax and MAPP gas (as I know some do for small couples for gold melting) would that be a good idea or just a waste of time?

Thanks!

[Frosty]

Ah HAH we're typing at the same time! If I had a can I'd have to experiment and see if I could get it to harden up, otherwise I'd put it on a shelf in case I found something to do with it. I've had half a can for probably 20 years what I applied to my forge liner rubbed off probably 18-19 years ago. It stayed chalky and I'd have to look in deep seams or cracks to find any now.

There's a lot of confusion about kiln washes, some think they're IR reflectors but they're actually re radiators. That means they conduct heat more slowly so they get hotter and then radiate the heat. Half goes back into the forge the other half goes into the liner. 

The "almost diamond hard" thing about ITC 100 relates to it's containing zirconium silicate which is almost diamond hard. The binder is kaolin clay and doesn't fire like pottery so it does not get hard. While it contains extremely hard particles the over all product doesn't get very hard.

Please bear in mind the above is MY experience using the product and yes I followed the directions that came with it. I wouldn't buy another can if it were 1/4 the price. It's very effective for what it is formulated to do, act as a release agent in pottery kilns, it prevents glazes and pottery from firing to the kiln furniture.

Either Plistex or Matrikote are excellent kiln washes for our purposes. They fire porcelain HARD to the walls of our forges, withstands the rapid thermal cycling a propane forge is famous for and is very resistant to: mechanical and chemical erosion. Scraping with work and being coated with welding flux.

Some of us have played around with making high % zirconia silicate kiln washes. I added 3 pts Zircopax to 1 pt. sifted Kastolite 30 and it's ugly but has stayed the course for a couple years of occasional use. Other folk have had good results with approx less than 3% bentonite clay to 97% zircopax. He's using a clay called "Bentone" in the Netherlands but there are lots of clays in the bentonite group to play with. I've had interesting results plopping bentonite at toothpaste consistency directly in a yellow hot forge and it fired hard in about 5 minutes. The cool effect is it foamed as the water boiled out and it fired. I haven't figured out how to use that little effect though.

Anyway, as you may have guessed we've been talking about forges, liners and washes a LOT. 

Frosty The Lucky.