Gary Finfrock on thu 29 dec 05
Hi,
I have an old recipe for a glaze called Raspberry that uses 5% Tin Oxide
and 0.15% Chrome Oxide to produce a nice semi transparent reddish color. The
problem is the glaze has some problems and therefore I went looking for a
replacement base glaze. I have tried several bases and cannot get the metal
oxides to produce anything near the color of the original Raspberry recipe.
The three bases I tried are two from the archives, Hansen's 5 X 20, and
the base from Val Cushing's Turquoise glaze. The third base was Laguna's WC-520
clear cone 5 to 10 glaze. This was the only base that produced anything in
the red range. It fired to a flesh color possibly a light pink with a tad of
inagination. The other bases only produced a gray color.
I'm certainly no glaze guru but I suspect either something in those
bases impede the color development, or another ingredient is missing that allows
the red color to happen. Any ideas?
Thanks,
Gary Finfrock
Inverness, Florida
John Hesselberth on fri 30 dec 05
Hi gary,
Chrome/Tin pinks are touchy. What temperature/cone are you firing to?
Since you have tried 5 x 20, I will assume cone 6. A primary
requirement is a high-calcium glaze and 5x20 doesn't have enough. But
there are some subtle other requirements which are not well
understood. Glazes containing ball clay and/or Gerstley Borate do
better than those that have neither. There must be a trace impurity
in those which helps the color develop. You might try the Raspberry
that is in Mastering Cone 6 Glazes. It is the result of perhaps 30 or
more experiments before I got a reasonably reliable and deep
raspberry color.
But it can be fun to try to find your own too. Just get some glaze
calculation software to guide you and go to work.
Regards,
John
On Dec 29, 2005, at 8:50 PM, Gary Finfrock wrote:
> I have an old recipe for a glaze called Raspberry that uses 5%
> Tin Oxide
> and 0.15% Chrome Oxide to produce a nice semi transparent reddish
> color. The
> problem is the glaze has some problems and therefore I went looking
> for a
> replacement base glaze. I have tried several bases and cannot get
> the metal
> oxides to produce anything near the color of the original Raspberry
> recipe.
>
> The three bases I tried are two from the archives, Hansen's 5 X
> 20, and
> the base from Val Cushing's Turquoise glaze. The third base was
> Laguna's WC-520
> clear cone 5 to 10 glaze. This was the only base that produced
> anything in
> the red range. It fired to a flesh color possibly a light pink
> with a tad of
> inagination. The other bases only produced a gray color.
>
> I'm certainly no glaze guru but I suspect either something in
> those
> bases impede the color development, or another ingredient is
> missing that allows
> the red color to happen. Any ideas?
John Britt on fri 30 dec 05
Gary,
I can't find my notes right now but I do have this recipe:
Plum Red (Chrome/ Tin) cone 6
Custer Feldspar 25.50
Whiting 28.20
Silica 22.10
EPK China Clay 13.60
Gerstley Borate 10.60
Chrome Oxide 0.50
Tin Oxide 9.00
I remember it working pretty well. Search the archives for Plum or red or
chrome tin and there should be some good recipes.
You can also vary the amount of tin oxide and chrome oxide. You may reduce
the tin to 7% and the chrome to 0.2 or so. Just find the color you like.
If you can't find anything acceptable I may find my book by then. I am
sure I have Raspberry and many others.
John Britt
President of the Glaze Free Trade Society
www.johnbrittpottery.com
| |
|
