search  current discussion  categories  techniques - misc 

mocha and bristol

updated wed 19 jan 05

 

Lili Krakowski on mon 17 jan 05


Kate

First, as Snail said, and I am not quoting directly, there are a number =
of variables. I have found that the slip I use, the glaze Iuse over it, =
the mocha solution all affect the results. =20

You may want to use a stronger (5%, 7% vinegar). You may want to try =
extremely strong tea (soak a teabag in 1/2 c. water, boil for a few =
minutes, squeeze out every drop.) My own dire suspicion is that the =
old timers used chewing tobacco and got their "solution" out of the =
spittoon. You might want to experiment with adding a drop of glycerine =
to your mocha mix. =20

you may want to try a slip mostly clay, and one less plastic; and you =
have to get ITS thickness right. Once you got it you got it, but till =
you do may take a bit of time.

Now as to Bristol glazes. Parmelee writes: The Bristol glaze is a =
variant of the soft porcelain type, adapted to produce an opaque white =
coating on stoneware and similar colored clay bodies.....The opacity and =
easier fusability are in part attributable to considerable amounts of =
zinc oxide used in the glaze composition." He adds that the Bristol =
glazes also can be "clear (colorless), colored, glossy, dull, or matt. =20

Most curious is that for a formula 0.35KNaO, 0.35 CaO, 0.30ZnO, 0.55 =
Al2O3, 3.30 SiO2 he speaks of "stoneware fired at cones 6-7 in 50-60 =
hours" !!!!!!!!!!





Lili Krakowski


Be of good courage

Rick Hamelin on tue 18 jan 05


Just a few things to mention, taken from several sources:
Bristol Pottery was 18th century English pottery making pearlware; Pearlware was the base body for Mocha, although not manufactured at this pot works. Certainly a fritted lead glaze.
Bristol Ware was a pale body stoneware "dipped in leadless glazes of ochreous brown on the upper part, yellowish cream on the lower" created by Amatt in 1835 and copied at the Doulton works. Eventually, it became a generic term for yellowish-brown wares that are not all stonewares.
Bristol Delftware was an English delftware (tin-glazed) pottery made from the second half of the 17th c to the last quarter of the 18th.
Bristol blue is a fine quality of smalts (cobalt) made available to British potters by the Prussians after their ware with Saxony (1756-63) which was previously banned.
Bristol Glaze was a once fired ware, "transparent, opaque or coloured but the original used at Bristol was probably opaque white consisting of zinc oxide, potash, lime, silica and alumina. Lead oxide was never used..They are frequently to be found on stoneware storage jars and bottles, hotel ware and sanitary ware."
"You say Bristol, I say tomato"
Rick

--
"Many a wiser men than I hath
gone to pot." 1649

-------------- Original message --------------

> Kate
>
> First, as Snail said, and I am not quoting directly, there are a number of
> variables. I have found that the slip I use, the glaze Iuse over it, the mocha
> solution all affect the results.
>
> You may want to use a stronger (5%, 7% vinegar). You may want to try extremely
> strong tea (soak a teabag in 1/2 c. water, boil for a few minutes, squeeze out
> every drop.) My own dire suspicion is that the old timers used chewing tobacco
> and got their "solution" out of the spittoon. You might want to experiment with
> adding a drop of glycerine to your mocha mix.
>
> you may want to try a slip mostly clay, and one less plastic; and you have to
> get ITS thickness right. Once you got it you got it, but till you do may take a
> bit of time.
>
> Now as to Bristol glazes. Parmelee writes: The Bristol glaze is a variant of
> the soft porcelain type, adapted to produce an opaque white coating on stoneware
> and similar colored clay bodies.....The opacity and easier fusability are in
> part attributable to considerable amounts of zinc oxide used in the glaze
> composition." He adds that the Bristol glazes also can be "clear (colorless),
> colored, glossy, dull, or matt.
>
> Most curious is that for a formula 0.35KNaO, 0.35 CaO, 0.30ZnO, 0.55 Al2O3, 3.30
> SiO2 he speaks of "stoneware fired at cones 6-7 in 50-60 hours" !!!!!!!!!!
>
>
>
>
>
> Lili Krakowski
>
>
> Be of good courage
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.