bill edwards on thu 22 sep 05
My old notes tell me that I used 0.45 chrome and 5 Tin
for a deeper darker version of chrome tin red. I am
thinking a small amount of iron to that may go
burgundy. I would check by line blending 0.25%
increments. Most these glazes with low AL203 high
calcium and contains boron with only tin will pick up
pink from any source of chromium in the kiln for
pinking of whites even after the firing when you have
no chromium in your kiln.
Tin White with a good balance of Al203 and Silica with
reduced calcium where Alumina is over 12%, silica is
above 59% and calcium is below 10% by weight, the Tin
Whites seem stable/balanced enough not to pick up
pinks from chromium glaze. Al:Si ratio being over 8
Reduce boron when you reduce the calcium load where
possible or watch the melt. Aim for C.O.E. below
10.000. (we aren't talking about food surfaces and
this is a low chromium glaze) we can talk lab latter.
What I ponder is why some don't consider the clay they
use being as important in its make-up as glazes? Often
a change in clay will result in completely different
end results and sometimes a much better fit. I think I
know a book or two that demonstrates these changes. On
Porcelain using a CTR you might see an apple red color
and on a red stoneware you might see a nice burgundy
usually because of the Fe in the clay. My next guess
would be to compensate for that on lighter clays. Let
glaze host the addition of color. Glazes for me are
supposed to be trained for action and re-action and
thats how and where so much testing on my end has came
from. I do promise to stop this over-flow in a few
days once I de-stress from all the hurricane talk!!!!
Calcium and Boron appear to be best buddies in these
glazes. If you have a high calcium glaze with a
matched high boron glaze but the rest is balanced
within limits otherwise, often you will see clearer
clears less the colorant oxides.
Lana Wilsons red is a great place to work from and
there should be no reason why Ron's wouldn't work the
same with some exercises in glaze testing. Too thin
and you get gray under-tones. Control the application
so you get a nice cover. This glaze usually lays well
on the surface and isn't overly fussy. You can handle
the glaze surface once dry without it slipping off
under your fingers. CMC or sodium alginate also will
tighten up a glaze for more durable handling for
glazes that are dusty and hard to deal with upon
drying. I have added epsom salt to her formulation
without problems. This might help some out there who
are exploring the red zone? And last but never the
least, do a grid, forget about 'just' calculating in
this case. Both will save you lots of time and effort
down the road when you combine the two.
Bill Edwards
Edmar Studio and Gallery
302 South Main St (Shipping)
POB 367 (Mailing)
Camp Hill, Al. 36850
http://apottersmark.blogspot.com/
Katrina Evacuee's BLOG
http://katrinaopelika.blogspot.com/
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