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41819Re: [hobbicast] Re: Colloidal silica supplier in Australia?

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  • michael.a.porter@comcast.net
    May 10, 2012
      It most certainly is a case of language dividing us, but not in any colloquial sense. I'm sure we've all had to "learn the facts of life" on more than one sad occasion. One of those unpleasant realities has to do with technical language, which is produced much less by technicians, than by manufacturer's sales staffs. You're not alone when confused and frustrated by technical terms. I was surprised by the volume of complaints my first book generated on that score; it was simplified to the furthest extent of my ability, but contained lots of common tech terms.

      But here's the ugly little secret; when it comes to technical terms we are all constrained by the need to actually buy products. At such a point we have to play by the manufacturer's (and therefore the retailer's) rules. Especially here in America, the customer is pampered (more like jollied along--before the sale). "Have it your way" and "the customer is always right" are familiar little sales jingles. Well, that all stops cold once you enter a welding supply dealership, and ask to purchase a particular MIG contact tip. Your sale isn't worth the clerk's time, and if you don't want to be told "I never heard of that" and shown the door, you'd better at least have your technical descriptions correct. Across the pond its going to be a different set of terms, but not a nicer set of rules.

      Rigidizer, while sometimes alumina/silica based for products like Duraboard and Durablanket, is nearly always colloidal silica. Ceramic fibers are quite flexible; in fact, that's their whole point of existence. However, once we get them installed, their flexibility often becomes problematic (kind of like the morning after the night before). It is fine to say "add two extra inches to its length, and force the blanket in under pressure; that will hold it in place." Unfortunately, left that way, the product will eventually shrink, and then sag out of shape after extensive heating.

      A layer of colloidal silica within the hot-face side of fiber blanket, locks the fibers into place against each other by gluing them together at every intersection. So, you gain a lot of structural integrity while preventing shrinkage to a large extent; both desirable outcomes.

      What it does not do is seal the fiber blanket or board. Air and hot gases still go right through the fibers if blown directly at them. Both ceramic fiber and colloidal silica form cristabolite upon reaching 1600 degrees F. You can look up cristabolite under "suspected carcinogen." So, it's a good idea to seal the fiber surface with a solid refractory coating; when the coating thickness is deliberately extended to any given refractory product's limit (think brick mortar for instance), then that coating is referred to as a "shell" and adds its own element to structural and thermal integrity.

      Happily, the rigidized layer supports the "shell" of ceramic sealant far better than a fiber product ever could (ceramic fiber products delaminate easily). At the same time the shell helps to greatly toughen the rigidized layer against impact damage. Finally, the solid refractory shell makes a much more stable base for the infrared reflector coating; a win-win situation all around.

      ITC-100 basically consists of zirconia particles, and a binder, in a minimal amount of water. I have strong reason to believe that binder is kaolin clay. I have no idea where to find anything in France (Okay, so I can find the Eiffel Tower; but nothing smaller). Zirconia powder is the finely ground crystaline form of metallic zirconium. Try looking under Zirconium dioxide (ZrO2),

      ----- Original Message -----
      From: Matthew Tinker <mattinker@...>
      To: hobbicast@yahoogroups.com
      Sent: Thu, 10 May 2012 18:11:35 -0000 (UTC)
      Subject: Re: [hobbicast] Re: Colloidal silica supplier in Australia?


      Sorry to be a bore, but I'm perplexed! Sounds like another case of or common language that divides us! OK, from what I understood, your making heat resistant coatings that aren't a "shell"; it is only a support structure. (sounds medical) Not sure I follow the difference.

      I'm very interested in this whole process, as ITC-100 Is very hard to find here In France (long time ex-pat Brit) the nearest supplier that I have found is in Ireland cost an arm and a leg! What is fine zirconia powder, sounds sci-fi, (What sort of place sells it?) Kaolin in powdered form is easy, (sigh of relief) powdered porcelain clay. What quantity is "and tosses in some left over" not sure I follow the proportions.

      I do know how a surf board is built, which is positive!

      regards, Matthew

      Matthew TINKER

      CNC conversion 1944 Colchester Lathe build-up log
      http://sz0093.ev.mail.comcast.net/zimbra/h/%3Cspan%20class=" yui-spellcheck?>http://sz0093.ev.mail.comcast.net/zimbra/h/%3Cspan%20class=" yui-spellcheck?>http://sz0093.ev.mail.comcast.net/zimbra/h/%3Cspan%20class=" yui-spellcheck?>http://www.cnczone.com/forums/showthread.php?t=35519" target=_blank>http://www.cnczone.com/forums/showthread.php?t=35519


      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 :-)


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