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41815Re: [hobbicast] Re: Colloidal silica supplier in Australia?

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  • michael.a.porter@comcast.net
    May 10, 2012
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      Old Iron in Oz,:

      Thanks right back at you. I will use what you just taught me about suppliers there. Believe it or not, finding such facts ain't easy; not easy at all.

      You asked:

      1. "Do I have to watch out for particle size?"

      No; colloidal particles are by definition light enough to remain suspended in water. As to larger particles; they fall out of suspension, and collect on the container's bottom. Years back, while doing experiments with ITC-100 (infrared reflective coating), I deliberately mixed some into a jar of water, and watched the coarser particles fall out of suspension; then did that with a whole pint of the stuff. After painting the colloidal portion on a forge interior, it went from orange-yellow to yellow-white; indicating a big lift in interior temperatures. The change was because, the finer the particle size the higher the percentage of reflected light. When I read the phrase "up to" in ITC-100's product description, I started checking. Don't forget some "colloidal" food coloring; it really helps in judging penetration.

      2." When I buy my sack of fumed silica powder, how do I mix it correctly to turn it into a colloid that will work well for building the ceramic shell?"

      Just keep dumping the colloidal silica into a jug of water as long as it will remain in suspension, or until it starts to thicken (the biggest advantage of colloidal silica over water glass is its ability to penetrate ceramic fiber well). Please, don't think of this layer as a "shell"; it is only a support structure.

      Soooo...what does we do with the rest of the colloidal silica, 'ey matey?
      Why, we uses it as a braugh bit o' binder 'ta mix with some kaolin clay (powdered form from a local potter's supply), and tosses in some left over fine zirconia powder that we bought 'ta mix with a dab of the clay powder that we's usin' as a binder for the zirconia in our homemade IR reflective coating, which we is paintin' over the ceramic shell that we's coatin' (1/8" thick) over the rigidified (what a jawbreaker) ceramic fiber (1/2" to 3/4" thick) after we cures it in the fire till it's nice and hard. We does the same to the shell coating before paintin' on a relfective coating.

      Of coarse, you needn't go to all that bother, but if you consider the construction of a typical surf board, the point of it all should become clear. Besides, you seldom have such an elegant (in the engineering sense) opportunity to get so much milage out of leftovers :-)

      ----- Original Message -----
      From: old_iron_oz <old_iron_oz@...>
      To: hobbicast@yahoogroups.com
      Sent: Wed, 09 May 2012 09:56:47 -0000 (UTC)
      Subject: [hobbicast] Re: Colloidal silica supplier in Australia?

      Ok, Michael, that's a great lead. I've found 'silica fume' is used as a concrete additive, and in that form is available in bulk in Australia; also there is a supplier here of food-grade 'pyrogenic silica' manufactured in Germany by Wacker Group. Presumably since this stuff appears in everything from milkshakes to toothpaste to cosmetics to cat litter and many more besides, it should be available via other industry suppliers here in Australia too, but none that Google found.

      So anyway, because I am new to this, two further questions stand out:

      1. Do I have to watch out for particle size?

      2. When I buy my sack of fumed silica powder, how do I mix it correctly to turn it into a colloid that will work well for building the ceramic shell?

      [Non-text portions of this message have been removed]
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