What about Sodium Silicate?

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What about Sodium Silicate?

Postby Nirky » Thu Mar 26, 2015 3:03 am

So I'm going to rebuild my RMH this off-season. Was going to substitute the firebricks with either castable refractory cement or maybe even try ceramic sheet.

Then two weeks ago I watched several YT videos where people made forges using a mixture of perlite/aluminum oxide/sodium silicate.
Here's one: https://www.youtube.com/watch?v=vQN7EqGMTuo

That mixture looks to be even more insulative than our standard perlite/fire clay/furnace cement mixture. And it appears to be harder as well. Anyone tried this sodium silicate as a binder for a core or a heat riser?
I don't think I'll ever get over Macho Grande, those wounds run pretty deep.
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Re: What about Sodium Silicate?

Postby matt walker » Thu Mar 26, 2015 5:35 am

Here's a link to Dave's experiments with that sort of mix:

http://donkey32.proboards.com/thread/12 ... ent?page=2

My mix uses the furnace cement as an easy way to add alumina and SoSi, but I do still have the clay as the main body of the binder. I have never tried a mix that didn't have clay.
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Re: What about Sodium Silicate?

Postby Nirky » Thu Mar 26, 2015 6:56 am

Thanks Matt, I read that thread. Guess there is no free lunch, so to speak. The riser can only have so much perlite, because it softens first. Needs the fire clay or aluminum oxide or other high temp resistant material to help support the insulating perlite.

Would a ceramic castable core & riser like in your Walker stoves be more insulative than fire bricks?
I don't think I'll ever get over Macho Grande, those wounds run pretty deep.
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Re: What about Sodium Silicate?

Postby matt walker » Thu Mar 26, 2015 2:38 pm

Yes, a lot more insualtive. At this point in my experimenting I'm of the mind that if one doesn't want the fun of experimenting and researching as a past time, the off the shelf insulated castables are a great material for the build. I like a density of around 60-70lbs/cu.ft, which I imagine translates to around half as dense as a normal firebrick. Insulating value should roughly follow the density ratio there.
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