[Clayart] Glaze SG question

Joe Brecha via Clayart clayart at lists.clayartworld.com
Fri Feb 27 13:46:08 EST 2015


First I would bisque lower. 06 or lower will absorb water better. Porcelain
is tighter than stoneware and if bisque fired too hot it will not suck the
water in as well. Second, see if you have flocculated the glaze too much.
Too much Epsom salts will mess up the drying. Third, make sure your glaze
specific gravity is high enough. Fourth, Make sure the pots are not wet from
cleaning. A good article to look at is the one on crawling in the March 2015
Ceramic Monthly. Joe Brecha

-----Original Message-----
From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf Of
Taylor Hendrix via Clayart
Sent: Thursday, February 26, 2015 6:48 PM
To: Clayart posting
Subject: [Clayart] Glaze SG question

I've a question for the hive mind. First I will state the knowns which
will, hopefully, circumscribe a limited area for useful conjecture. Yea,
right.

I have several ^6 glazes in the Art Center's clay studio that have SG of
1.14 to 1.23 as measured by me with a scale. They appear to be good for
dipping.

I have a clay body (^6 porcelain from Armadillo Clay in TX) which is being
dipped in the glazes.

I bisque student pots to cone 04, cones bend properly.

Student pieces do have variable wall thickness from rim to foot expected of
beginner to intermediate throwers. Some pieces quite on the thin side, some
much thicker.

Several of the glazes are NOT drying on the bisque ware with sufficient
rapidity to prevent entire sections of glaze to continue reacting to
gravity once the item has been righted and placed on the table, tongues
removed. Many of the pieces remain wet to the touch for many minutes. These
are not errant drips, but rather entire surfaces that flow down the form.

I believe that these glazes have not only too much water but also have
ingredients that make them behave as if they were thick enough for dipping.
Where the cross section of bisque is insufficient to contain the moisture
of the applied raw glaze, we see the glaze remaining fluid on the bisque
for several minutes.

I may or may not be able to confirm that Gerstly B. is one of the
ingredients in many or all of these glazes or if a particular glaze has a
preponderance of frit.

-->  Question: Is SG of 1.14 a workable number for ANY type of ^6 glaze
which one applies by dipping, or is my suspicion that the glaze is soupy
correct?

I have been adjusting my own personal glaze to SG 1.43 for quick dipping,
so I have no current experience with such low SG numbers in my home studio.

As a side note: I can't confirm this, but one student noticed that
different clay bodies had different results to the same glaze dipped. Some
dried just fine, some took a longer time to dry.

Thanks for helping me confirm or deny my suspicions.


Taylor, in Rockport TX
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http://wirerabbit.blogspot.com
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