iandol on wed 2 apr 03
Dear Sylvia,
Another idea is to pack weeds or straw which have been soaked in salt =
between your pots, a technique known as Hidasuki in Japanese circles.
It is a mistake to think that Common Salt, Sodium Chloride will =
volatilise to any great degree until the temperature approaches its =
boiling point 1413 deg Celsius at atmospheric pressure.
To draw a comparable analogy, consider how long you would have to boil a =
pan containing a litre of water before it boiled dry at 100 deg Celsius =
and compare that to a litre of water held at Eighty or Ninety degrees =
Celsius. Yes, it evaporates, eventually. So you may need to hold your =
top temperature of your dispensation saucers for a longer period to get =
a more pronounced effect.
In the normal course of events in a Saltglaze firing Coarse Salt gets =
scattered around a kiln as a fine powder due to Decrepitation, minor =
explosions, when it is heated suddenly. Try holding a large crystal of =
softener salt in forceps and heat it in a propane flame to observe this =
effect. Wear Goggles please.
If the temperature is high enough small fragments usually melt, 801 deg =
Celsius. So in a normal salt firing the powder becomes droplets which =
fall or get wafted onto the ware in the kiln. !!
Enjoy your work.
Best regards,
Ivor Lewis.
John Britt on thu 3 apr 03
Ivor wrote:
"It is a mistake to think that Common Salt, Sodium Chloride will
volatilise to any great degree until the temperature approaches its
boiling point 1413 deg Celsius at atmospheric pressure."
This may be a theoritically true but in practice, I have done a melt tests
with salt and it "went away" at a very low temperature (1547 F). (Maybe it
soaked into the body?) I also know it melts into a flat test tile clay
body at cone 10 (2350 F).
How can you explain this?
How do you explain salt firing? It sure does look like it volitalizes
when you put it in a kiln.
Looking for scientific clarification,
John Britt
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