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Ross Jones

Does Borax Eat Insboard?

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I'm making my new forge and I'm thinking of using insboard as a sacrificial floor on top of 2" thick inswool. The typical hard firebricks I find that I used for the floor of my last forge aren't long enough for this one. Would insboard make a good replaceable floor, should it be coated, or is this a bunk idea entirely? Thanks for any help you can give. 

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Yes, it eats it. Fast. 

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What if you line your insboard with refractory cement? You could make high borders to prevent drips. Just my 2 cents

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The only refractories that stand up to borax for long are the castables, bubble alumina, and hard brick.  Satanite holds up okay as long as it's at least half an inch thick, but any cracks allow the molten borax through to the wool or insboard, which will then disappear like cotton candy in hot water.  I have known people to use a pan made of heavy stainless, but you have to rake out the flux puddle while it's hot.  And even 10 gauge stainless warps and eventually goes away after enough firings.  

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I use hard fire brick floors with kaolin 'dams' on the sides, but when enough borax has built up it starts to run over the edges and eat the wool lining.   Eventually you just gota suck it up and re-line the forge =P

 

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I'm thinking of coating the floor of the forge with bubble alumina and putting a hard fire brick down on top of it. I'll get the that dam effect while hopefully minimizing damage to the lining. I was doing some googling today and saw some people posting about a refractory called "Pyramid Super air set" that reportedly is completely flux resistant and is rated for 4000f. I did my poking around through google and found out that the company that makes it went under. Is anyone still making a refractory similar to this?

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I'm not completely opposed to using a hard fire brick on the floor, but the bricks I find are typically 9" and the steel tool box I'm re purposing for the forge body is 15" long. I would just cut another brick to meet the missing 6", but I'd rather just have an insboard shelf I can slide in and out. I'm thinking the best way would be to coat the board in bubble alumina and replace it when necessary.  

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Kiln shelves is an option I'm looking into, they are cheap enough to be replaced occasionally and should be immune to flux.  Now if someone just made some with raised edges....

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A buddy of mine casts a welding tray out of Mizzou for his forge.  He has a mold set up, and puts a rectangular box in the middle so that there will be raised sides.  Whenever he welds, the tray goes in.  When it starts to wear out, he casts another.  Mizzou is cheap.

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That tray idea sounds really good.

I put a hard brick forge in mine before I coated it. Then I went over the brick with satanite and a coat of ITC.

I thought at the time I should leave it low in the center.

Now I have a lake of flux standing in the forge every time I fire it up.

If you want something that will hold the liquid flux, make sure it is removable.

 

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3 hours ago, Don Abbott said:

That tray idea sounds really good.

I put a hard brick forge in mine before I coated it. Then I went over the brick with satanite and a coat of ITC.

I thought at the time I should leave it low in the center.

Now I have a lake of flux standing in the forge every time I fire it up.

If you want something that will hold the liquid flux, make sure it is removable.

 

Ya, that tray works pretty well.  The only bad part is that it takes the forge a little longer to come up to heat because of the added thermal mass.  But, he never has a problem with flux in his forge since he takes the tray out for regular forging.

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After looking through all my options, I've decided to use bubble alumina for the floor along with coated fire bricks as a sacrificial floor. All of these options were really insightful and definitely things I'll be looking into, but my best personal option is to just suck it up and cut firebricks to fill that 6" gap. Thanks for all of your suggestions, it's amazing how much I learn from this forum!

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I feel that it should also be said: there is also always the option of not using borax.  Fluxless welding is a thing, and it does work if you can run your system right (as demonstrated by numerous people).  

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On 9/10/2017 at 6:37 PM, Justin Mercier said:

I use hard fire brick floors with kaolin 'dams' on the sides, but when enough borax has built up it starts to run over the edges and eat the wool lining.   Eventually you just gota suck it up and re-line the forge =P

 

what is the borax for? is it the flux

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5 minutes ago, Craig Rice said:

what is the borax for? is it the flux

Yes. It's commonly used for laundry, but smiths found a better use for it

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