jonathan edward byler on sun 10 dec 06
newcastle refractories (NCRCI.com) sells a high silica softbrick
rated to 2300F, which is 32% alumina, 64% silica... Anyone think
this might be the answer for the sodium vapour kiln? regular K-23's
from TC are 38% alumina, 44.3 silica, k-26 are 48% alumina, 36%
silica. only problem is that is not quite to cone 10 heat rating.
I am still leaning towards a hardbrick liner for now, for previously
mentioned reason of a higher heat retention on cooling in a
relatively small kiln. If that seems foolish to anyone, having a
high heat retention for slower cooling, I would like to know. I
understand industry goes through very fast heating/cooling cycles,
but I think that I will not have the capability to control things
quite that well, and will benefit form a slower cooling cycle. I
will try and get some of these bricks and test them in the kiln
environment, once we have things underway.
-jon
On Dec 10, 2006, at 6:45 PM, Vince Pitelka wrote:
> Ivor Lewis wrote
> "I have no experience of firing with Sodium Carbonate though I have
> built
> kilns for firing with Sodium Chloride. For several reasons my
> preference was
> to use dense high alumina stock and place an adequate sheathing of
> insulation around the core of the kiln. One thought that dominated my
> thinking ( in the early 80's) was that a porous brick would adsorb
> salt
> vapour. This would condense then solidify. Then, when the kiln was
> reheated
> and the salt melted it would act as a solvent and destroy the brick
> form
> inside. This was based on the knowledge that Sodium Carbonate
> fusion is used
> to render mineral samples water soluble for analysis, the molten
> substance
> having strong solvent properties."
>
> Ivor is right on in his statements above. High alumina in a brick
> is fine
> for wood firing or reduction firing, but not for salt or soda. As he
> states, the brick remains porous, and the sodium vapors enter the
> brick,
> causing internal breakdown and spalling of the hotface. It is a
> horrible
> thing to witness after one puts a great deal of time and money into
> kiln
> construction. We all know that an alumina-china clay wash resists
> salt
> deposition on furniture and shelves, but that is no indication of
> what will
> happen in a brick. In a salt or soda kiln, you need an impermeable
> barrier,
> and a higher-silica brick promotes surface glaze that effectively
> seals the
> brick from further vapor penetration. We always think of higher
> refractory
> as more durable and resistant, but in salt and soda kilns it
> requires a
> different mindset.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft, Tennessee Technological University
> Smithville TN 37166, 615/597-6801 x111
> vpitelka@dtccom.net, wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka/
> http://www.tntech.edu/craftcenter/
>
| |
|
