[TheForge] crucible furnace

[Michael]

Terry,
That is not a good idea. If I remember correctly, the various forms of water
glass liquefy somewhere between 1300 and 1500 degrees F. Since you are
dealing with a lid, rather than a lid and side walls in one lift up (Top Hat
type) unit, than I would suggest buying a round mullite kiln shelf (they are
cheaper than high-alumina and down-shock resistant)as your load bearing
hot-face. Drill an exhaust hole in its center with an old hole saw you don't
care about, or a few jigsaw blades (you can get carbide encrusted jigsaw
blades to use this way from a large hardware store, and drill a starting
hole with a drill bit you don't care about or a concrete bit). The kiln
shelf will support the Kaowool, and you only need rigidizer in the area
around the exhaust hole (it is sold in pints at some potter's supply
houses). Also, since you are making the side wall and lid as separate units,
you have the opportunity to fold the fiber blanket for the side wall
accordion style and compress it into a denser shape (more resistant to heat
shrink problems this way (Giberson likes to cut double layers and fold them
over, placing these "sandwiches" side by side until satisfied with the
amount of compression, than rigidize the inner face that the folds form with
zirconium).

A general comment to all:
I have often seen "The Kiln Book" recommended as a general guide to building
hot-work equipment. It is a wonderful book if you want to build a LARGE
kiln, but very little use to builders of smaller heating equipment. I would
instead recommend "A Glassblower's Companion" by Dudley F. Giberson, Jr. By
the time you've read your way through the relevant sections of this book
(some of the equipment is only of interest to glass artists) you will feel
pretty bold about designing your own. Also, his ideas about home made
insulations are much better than what I see posted on the web. 
Mikey


-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net] On Behalf Of terry l. ridder
Sent: Saturday, September 09, 2006 7:39 PM
To: Sponsored by ABANA
Subject: RE: [TheForge] crucible furnace

hello;

comments below;

On Sat, 9 Sep 2006, Michael wrote:

mikey>
mikey> The Kaowool with ITC #100 will certainly take any heat source
mikey> that a home-made bottom refractory will, especially if you buy
mikey> some rigidizer and stiffen the inside face to about 1/2" depth
mikey> before using the ITC #100 coating. Otherwise, you will have
mikey> trouble, not on the vertical portion, but the overhead and
mikey> exit hole. You will find the furnace to be surprisingly efficient
mikey> this way.
mikey> 
mikey> Mikey 
mikey> 

the lid may present trouble but it really depends on how the kaowool is
placed in the lid. most people would probably just cut two circles and
place them in the lid. this would present a problem unless some
rigidizer was used on the circles. i was thinking about making strips
three inches wide by 1 inch thick as long as the roll. wind the strips
in the lid in a spiral until i get to the exhaust hole. i also toyed
with the idea of painting the strips with sodium silicate. i have one
gallon of sodium silicate.

or i could just line the lid with the homebrew refractory.

-- 
terry l. ridder ><>
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