Dori Grandstrand on mon 17 sep 01
Hello All,
I brand new to this group, a relative babe-in-the-woods with ceramics, and
after reviewing tons of postings to find answers to my questions, I am still
quite beffuddled and would appreciate any help you can give me on the
following:
I am currently working with Dove Porcelain and Dove Slip (from Seattle
Pottery Supply), colored with Mason Stains (for sgraffito), with a clear
glaze over and fired to Cone 6 (at least that's what I'm aiming for!!).
First, I have tried many, many clear glaze recipes, but I am getting
crazing and/or small pitting; I'm wondering if I may simply be applying the
glaze too thick? Does anyone have a "bombproof" clear, glossy glaze at Cone
6 (electric)? (Yeah, I know, no such thing as bombproof, but maybe I can get
close?:) As to glaze fit, I am bisqueing at Cone 06, glaze at Cone 6.
Second, I have successfully formulated many of my own slip recipes with
various oxides, and have used Mason/Degussa stains for the more challenging
colors, but I just can't seem to get the colors to "develop" -- the Mason
purples/blues/pinks aren't coming through the firing as bright as they should
be, and the Degussa red and dark red only come through as pink. I know all
the stuff about using 15-20% whiting or wollastonite to develop the colors,
but they still aren't working, even though I've tried a variety of
transparent glaze formulas. What am I doing wrong - why aren't the colors
developing? Do I need to add whiting or wollastonite to the stained slip
base as well? (This is SOOOO crucial to me, any help from you folks and I
will be a devoted slave, forever:)))
If you need further info, such as the glaze formulas I am using, please
let me know, but since I have tried so many, including a few in this group, I
just don't think it's the glazes -- but something else. Once again, I would
truly appreciate your help, and will camp out here at the computer and
eagerly await your responses!
--- Dori Grandstrand, Sultanarts
John Hesselberth on mon 17 sep 01
on 9/17/01 9:42 PM, Dori Grandstrand at Sultanarts@AOL.COM wrote:
> First, I have tried many, many clear glaze recipes, but I am getting
> crazing and/or small pitting; I'm wondering if I may simply be applying the
> glaze too thick? Does anyone have a "bombproof" clear, glossy glaze at Cone
> 6 (electric)? (Yeah, I know, no such thing as bombproof, but maybe I can get
> close?:) As to glaze fit, I am bisqueing at Cone 06, glaze at Cone 6.
Hi Dori,
There is no such thing as a universal clear glossy craze-free glaze at cone
6 (or any other cone). Each glaze has to be matched to the clay because each
clay if different in its expansion/contraction characteristics. Post the
recipe for the glaze that crazes the least and someone will then be able to
suggest clear recipes with lower expansion coefficients that should not
craze or will at least come closer to not crazing. It may take a couple
iterations to get you where you need to be.
Regards, John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Martin Howard on tue 18 sep 01
Dori, while you experiment with making your own slips and glazes (and I know
the steep learning curve that process involves) why not take the easier
path?
Whoever markets your clay will also have links with some firm that markets
glazes developed for that particular clay.
Buy the slip and clear glaze they recommend.
Add bought stains or your own RMs to colour both slip and/or glaze.
It is easier, IMHE, to use stains only in the slip and then glaze clear.
That also has the added advantage that it is easy to check over whether you
have actually glazed all that your wanted to, because it will all have the
same white colour before going into the glaze firing.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Craig Martell on tue 18 sep 01
Hi Dori:
You may not be getting purples, reds, and pinks, because they are contained
in the slip and not in a glaze. These colors, some of which are
chrome/tin, are bound within the slip and are less affected by the
glaze. The slip oxides are not the best for making these colors dance and
very little is released into the glaze at the interface. You might try
applying these stains to leatherhard ware in a glaze that has a fair amount
of clay instead of using a slip. Select a glaze that is fairly well
supplied with calcium too. Do your scgraffito decoration thru the glaze
and bisque fire it on. Then apply your glazes over this and fire to cone
6. If the decorative glaze, with stains, is high enough in clay, I think
your designs will hold their edge. I know the colors will be more lively.
You could also try increasing the percentages of stain to the slips but
this could get real spendy.
regards, Craig Martell in Oregon
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