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Posted by Jacob Hawes on July 28, 2005, 5:21 pm
Please log in for more thread options What is the boiling and melting temperature for this stuff? Does it do
anything to hold in heat or does it just help bind fibers together?
jpolaski@rgs.uci.edu wrote:
> I should have been more clear. The colloidal silica is used as a
> coating for ceramic fiber to stabilize the fibers. If you use a
> gas-fired forge the fibers have a tendency to come loose during use.
> I'm certainly no expert, but I understnad that it's a health hazard.
>
> The silica forms a glass-like layer that helps to seal in all the
> fiber-ey goodness (and keep it out of my lungs). The layer is pretty
> brittle, though, especially at heat. It's good to have some brick or
> kiln shelf on the bottom of your kiln to lay the metal down on.
>
> This is my first forge, and I'm just begining this whole blacksmithing
> thing, so I'm certainly no expert... I'm just trying to share some of
> my experience with others. I'd certainly reccommend using the silica
> wash over any ceramic fiber... A couple of tips, though:
> Once the silica goes down it gets pretty crunchy. I thought I could
> spray some water on it to loosen it up a bit, but it doesn't seem to
> work that way. Once it's dry it's ridgid and pretty much staying in
> whatever shape it already has. In other words, don't coat the blanket,
> let it dry, and *then* try to form it with a little water.
> I've been brushing it on, but I think a cheap water-mister spray
> bottle would work better.
> The ceramic fiber crushes pretty easily, and a thin layer of silica
> breaks very easily, some times tearing a thin piece of blanket off with
> it. I think you're better off soaking the blanket. Also, I'd recommend
> using at *least* a two inch thick layer of blanket.
>
> Just to share a little of what I learned building my forge...
>
> First, let me qualify this by saying that it's far too easy (for me, at
> least) to get obsessed with the tools and not get a whole lot of work
> done, and you can easily do great work with just about *any* tools. So,
> if you're new to this, you shouldn't get too hung up on the exact forge
> design or anything, as long as it's safe and does what you want.
>
> After I built the forge, I realize that I was a little too focused on
> the burners, and not the forge body. For a gas forge I think that,
> given the choice between a super-efficient burner or a well-insulated
> forge, it's better to have a well-insulated forge.
>
> My thinking is that the working forge is analogous to a river flowing
> into a dam. The burner is like the river and the dam is like the forge.
> The amount of heat is like the level of water behind the dam. What you
> want is to get the level of water up as high as you can. No matter
> what, though, you're going to loose some water due to evaporation. If
> you open up the flood gates (i.e. loose a lot of heat) you're going to
> have to throw a lot more water in behind the dam to get the level to
> rise. If you close up the flood gates (i.e. insulate) you can have a
> relative *trickle* of water flowing in and the level will still rise.
>
> Focusing on burners is like adding more water without closing the flood
> gates. You can do it, and it will work fine, but you're going to use a
> lot more fuel than you need to. I think most people will be better off
> with "O.K." burners and more insulation.
>
> It's not a perfect analogy, but it should get the message across... Any
> comments?
>
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