John Hesselberth on fri 22 apr 05
On Apr 22, 2005, at 8:49 AM, Maxwell, Deborah wrote:
> What is the 3 day vinegar test?
Hi Deborah,
Take a glaze-fired test tile with your subject glaze on it. Submerse
half of it in vinegar--regular white or cider vinegar--makes no
difference. After 3 days remove the tile, rinse well, dry and let air
dry for a few more minutes. If you can see a difference in color
between submerged and unsubmerged sections of the tile, the glaze is
very unstable. If you can see a difference in sheen, but not color the
glaze is questionable. Good, durable glazes show no difference in sheen
or color after 3 days in vinegar.
This is a good screening test. For a quantifiable test you will have to
have your glazes professionally leach tested. But, frankly, I would be
happy if we could just get functional potters to not use lead and
cadmium and only use glazes that pass the 3 day vinegar test with no
change. That would be way ahead of where we are now.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Maxwell, Deborah on fri 22 apr 05
John
What is the 3 day vinegar test?
Deborah J. Bassett-Maxwell
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of John
Hesselberth
Sent: Thursday, April 21, 2005 7:44 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Floating Red/Foodsafe?
Hi Don,
This glaze is probably not be very durable (I don't use the term food
safe because there is no agreed-on definition for it) because it has
almost no alumina and a very low level of silica. It is hardly a
glaze--more of a surface treatment. I would not use it on functional
work unless it passes a 3 day vinegar test.
Regards,
John
On Wednesday, April 20, 2005, at 05:32 PM, Dori Grandstrand wrote:
> I have a glaze recipe (C6) called Floating Red -- can anyone tell me
> if it is foodsafe?
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