Did I poke beehive
The kiln is a man's best friend - before the dog.
We all love ours, and defend it.
My apologies for the wrong estimate of precision.
From now on I trust my thermocoupe to give
the temperature of the thermocouple.
The temp of the air is crucial at low temps.
At the upper range the radiation rules.
I noticed it yesterday when I had to put my hand
into a 700 C kiln to add some cullet
The sun shines equally to the good and evil
so does the kiln radiation. The shied of the TC
is luckily of the same whiteness as my mold materials
and absorbs the radiation the same way.
The glass in my mold behaves differently. It transmits
much of the radiation to the inside of the mold,
absorbs some and reflects the rest.
All this takes the ramping and soaking we are talking about.
COOLING
Jus now I have a simple open form in mu kiln
There id 6 kg glass in a 5.2 kg mold.
Almost half of the heat is stored in the mold.
It is a flat, openface mold with shallow sides.
It has only two ways to loose heat: thru the glass
and thru the shelf. That is why the mold thicknes
is included in the annealing formulae.
In the annealingphase I have to use top elements
toslow down the heat loss - to a rate that matches
the heat transmission from the bottom.
When I cast in a tall deeep form, there is very little exposed
glass area. All the heat must be lost thru the mold walls.
If they are of uneven thickness, uneven cooling
is unavoidable unless it is very very slow.
In fact I am annealing the mold, more than the glass.
HUGGING
Tony,
I am in cold and dark Finland.
I miss you all.
-lauri