[TheForge] Dear Tightwad

[Kathy]

Dear Tightwad,
The ITC #100 coating is thin; furthermore, it tends to develop unnoticed cracks
for superheated flux to penetrate. The zirconium coating does what it is suppose
to do--reflect IR energy and act as a seal for the ceramic fiber--very well.
BUT, the coating layer it forms is as delicate as an egg shell. There is nothing
stopping you from using the ITC #100 as a reflector coating over the Plistex. In
fact, the amount of rather expensive ITC #100 saved by painting on a sealed,
rather than absorbent surface, should more than cover the cost of the Plistex.
If Larry had offered Plistex before I wrote Gas Burners it would have been
featured in chapter five's forge; it will be featured in the eventual rewrite. 

Unfortunately, Larry Zoeller and others who sell blacksmithing tools and
supplies are a little TOO well behaved about not pushing their products on this
group; it sometimes creates an informational vacuum. Scroll to the lower part of
this page to find Plistex: http://www.zoellerforge.com/flare.html
While you're there, take a good long look at the other moderately priced forge
building supplies he carries.
Mikey  

-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net]
On Behalf Of IowaHarry
Sent: Wednesday, August 01, 2007 2:44 AM
To: Sponsored by ABANA
Subject: Re: [TheForge] A challenge to Harry

Mikey,

    One of the aricles I have seen in reference to ITC was how it 
protected the ceramic blanket from borax. I intend to put a piece of 
kiln shelf on the bottom so that takes the brunt of the banging around 
in there but the occasional twitch could cause borax to land in the 
wrong spot. For fuel efficiency and borax resistance, these are the main 
reasons I chose to go this route. I only do this as a hobby so, being a 
practicing tightwad I am trying to do it on the cheap.

Harry

Kathy wrote:
> Harry,
> ITC #100 is an infrared reflector (actually a re-radiator) the only protection
> it provides ceramic blanket is in cutting down the amount of conducted heat
> energy into the blanket's interior from its hot-face side; this protection is
> real, but is limited. Over time, the blanket will still overheat and shrink;
to
> understand this, look up both the dropping insulation values over an extended
> heating cycle, and the percentage of shrinkage expected as the heating cycles
> are repeated.  The first thing this shrinkage leads to is spalling of areas on
> the hot-face surface, because the ITC #100 coated area is unable to shrink
along
> with the rest of the ceramic blanket; instead, it temporarily expands somewhat
> from the great heat it is generating. If you are looking for a protective
> coating, rather than an IR reflector, you would probably be much better served
> by Plistex from Larry Zoeller. He showed me an treated sample at the ABANA
> conference in Kentucky. It was pretty impressive.