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Sodium Silicate and White bubbling- Forge Problems.


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So like many I'm new at this whole forge making thing- I've made a charcoal forge but its not that great and its a pain to set-up and clean-up so I'm working on a propane forge. I am using the per lite and sodium silicate mixture everyone's talking about but when I tried to heat my forge the smallest amount of heat made the sodium silicate bubble up. The bubbling is white, rocky, and strangely enough kinda looks like perlite (if perlite was a mold).  To make sure it was the sodium silicate I put some one a piece of wood and after it was hard I blow-torched it. The same thing happened, white, rocky, hard bubbles. The sodium silicate that I have I bought disguised as Cement Sealer because it was cheaper. I bought a Gallon for $50 and it claimed to be 100% sodium silicate. Whats wrong with it? Has this ever happened to anyone else? Here's a picture. I covered the perlite mixture with the refractory cement from CLKindred's forge making video. This Dark Grey cement lets you see the bubbling effect clearer. What in the world is that?


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The refractory insulation you have used may be the one that "everyone is talking about" on YouTube, but IMHO it is not suitable for a propane forge.  It has poor insulating value, isn't very durable and reportedly is prone to spalling.  If you read through the archives here on gas forge building you will come across many better options for insulating your forge.  Note that the insulation is just to allow you to heat your metal efficiently.  Any material to hold that heat can be used, just some are more energy efficient, safe and durable than others.

Hard to tell from the photo, but I don't see any burner port in your forge.  How were you planning on heating it?

I recommend use of high temperature glass fiber insulation blanket (Kaowool) with a thin skin coating of some form of high temperature refractory (satinite or the like) for a first forge.  Check out Wayne Coe's site for good information on forge construction.

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I must have missed the discussions on here about using the combination of perlite and sodium silicate together.  I've seen talks about the use of sodium silicate by itself as a rigidizer for ceramic fiber blanket, and I've seen discussions about using perlite in clay based home brew refractories to add insulating properties though.  Keep in mind that perlite is a highly porous material.  If you have it saturated in a water based mixture it will retain a lot of water that has to be driven off without turning to steam to avoid bubbling,cracking, or even small steam explosions taking chunks out of the lining.  That translates into a long drying time and slowly and uniformly bringing the temperature up inside the forge.  I'd say at least a week of drying without additional heat and then some time using a light bulb or some other relatively low temperature method before thinking about introducing an open flame. Of course all that is dependent on the ambient temperature and humidity in your location.

Beyond all that, as Latticino said, it's still not a very good choice for a propane forge lining.   There are lots of threads on here regarding building good propane forges and what to use for insulation and lining.  Pull up a chair, a drink, and something to eat and read for an hour or twelve on the topic and by the end of it you'll have a decent understanding of making a good propane forge.

I know the temptation to try to use cheap and easily available materials for your own home brew refractory, but the reality is that road will usually result in you spending far more money on propane in the long run due to the lower insulating properties of nearly all home brew mixtures.

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

Once again the internet shows just having a video camera and connection doesn't mean you have a clue about how to do things.  don't worry Cookie, I'm not gigging you it's the whole Youtube nonsense that's so generally destructive.

I don't know where it originated but the sodium silicate and perlite "refractory" myth is just that a myth. A person could MIGHT use it as a backer if there were enough good refractory between it and the flame. Perlite starts degrading rapidly around 2,000f, say the bright orange part of the camp fire when you blow on it. Pretty useless stuff unless you're using it to aerate and hold moisture in potting soil.

As recommended already, pull up a comfy chair, beverage of your choice some snacks and settle in for some high quality reading. Of course you'll need to learn to filter the chaff from the grain, some of the same guys producing such frankly useless Youtube video how tos post here and there are a raft of new guys wanting to be helpful posting THEIR opinions. Believe it or not you HAVE to know enough to realize how little you know and only THEN can you really start learning stuff. Heck anything.

Don't worry, it's just part of the learning curve, we all had to start somewhere.

Oh the reason that stuff is foaming up on you is it's #1, not dry yet and #2, not capable of withstanding that much heat.

Frosty The Lucky.

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HA! You called me Cookie XD  (Thats hilarious)

Thanks for the warm welcome! You guys are very inviting and seriously very helpful. You may be right, I think the sodium silicate isn't cured yet- I completely forgot to check the curing time. Thanks for the warning about humidity, im in WI were there used to be a swamp- so it can get quite humid and I've already had a plaster mold spew molten aluminum at me. One more question before I dive into your forums. I made Grant Thompson's Charcoal Mini Foundry and the plaster/sand mix after one use practically all fell apart and is now extremely fragile. Do anything to the plaster and it would all fall apart. Is that because I didn't slowly heat it up to remove moister?

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Well, yes I did we don't know each other well enough for me to refer to you by your creamy center. :rolleyes:

Maybe I wasn't clear enough, I tend to go all long winded and can lose my point. It's a TBI thing. Anyway, cured or not sodium silicate will NOT make a suitable forge liner. It has  specific purposes in a gas forge but not in any concentration in the flame face. CO2 breaks the sodium silicate bond leaving the silicate coating everything.

Anyway, a perlite sodium silicate, concrete(?) just can't withstand the heat of a gas forge. You can let that stuff cure till you're old and grey and it'll degrade under a torch as soon as it gets hot.

Plaster of Paris is an even worse material for a refractory it's actually dangerous to be around if you get it hot enough fast enough. Crumbling is how it reacts to high heat in a safe manner, heat it fast and it tends to spall violently. Little steam explosions blasting HOT chips around the area.

The sand is okay, no problem with sand. Mix approx 1pt. clay with 2-3pts sand. Add just enough moisture you can squeeze it into a hard lump in your fist that breaks cleanly and you have the makings of a "decent" temporary liner or fire brick. Not very high temp unless you use fire clay but it'll do for a camp oven or survival fire place. With practice you can build a kiln and fire home made brick for a pretty permanent building material.

If you want to make stiff mud then you really need straw in the mix or it'll shrink check as it dries and you end up with crumbles.

If you check out the Alaska Association section we've been discussing castable refractories. I'd mention the other thread going right now but my memory is shot another TBI issue and worse I just heard about the Police officers killed and wounded in an ambush attack in Dallas so I'm not remembering things I should.

Anyway, there seems to be a consensus of experienced users that Kast-O-Lite 30, a 3,000f castable, high alumina, bubble refractory has virtually all the characteristics that make an excellent gas forge liner. The Alaska price is $77.78 per 55lb. bag.

My advice to you my friend is FORGET making your own refractory and buy a bag. You could get rich mowing lawns with the time you save on experimenting and fiddling a good home brew refractory. Well, buy a decent used car and be using a forge.

Frosty The Lucky.

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Just to put in my 2 cents, again, regarding the Kastolite 30.  I do agree that it will make an acceptable inner forge liner, but need to note that it is a significantly poorer insulator and greater thermal mass than refractory blanket insulation.  Practically this means that you need almost four times the thickness of Kastolite to get the same insulating value as the same thickness of blanket (and the extra mass will lead to slower times to get up to usable heat). 

If you want to get the equivalent of 2" thickness of 6# high temperature blanket you could go with 1" of blanket (could be lower temperature rated) and an inner liner of 4" of Kastolite, but that doesn't seem too practical to me.  I think a better solution would be to look at 2" of 2300 degree blanket (or insulating soft brick) wrapped around 3/4" of Kastolite set inside some kind of steel enclosure to keep the blanket from getting damaged, but that is just me (and I may be misinterpreting the manufacturer's data).  By all means try it and see how it works; anxious to hear your results.  I do still have a 5" thick furnace door that I cast out of Kastolite many years ago for my glass furnace.  It held up just fine to 2,200 deg. F temperatures and provided good insulation.  Of course I always took days to heat the furnace up or down, so I have no idea how it would respond to rapid thermal cycling.

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