Randy McCall on thu 11 sep 08
A number of years ago I mixed up a batch of June Perry's Red and the raw
glaze had a definite green color to it. When I mixed up a recent batch the
glaze wasn't even close to green with .5% chrome raw glaze. The original
mixture came out a dark apple red with a very smooth waxy texture. I wonder
if I might have used 2% chrome instead of the .2% small amount? Would 2%
still work in this glaze or would that be too much chrome. Are there limits
in chrome that can be used in chrome red glazes. This glaze will turn a
splochy white where thin and must be put on a even thick.
Recipe Name: Shamhbhala Chrome Red
Cone: 6 Color: Burgundy
Firing: Oxidation Surface: Glossy
Amount Ingredient
21 Gerstley Borate--1999
16 Nepheline Syenite
11 Ball Clay Number 1
20 Whiting
32 Silica
100 Total
Additives
.2 Chromium Oxide
5 Tin Oxide
Unity Oxide
.112 Na2O
.027 K2O
.007 MgO
.854 CaO
1.000 Total
.272 Al2O3
.246 B2O3
.003 Fe2O3
2.811 SiO2
.005 TiO2
10.3 Ratio
70.1 Exp
Comments: NICE BURGUNDY NEEDS TO BE THICK DIPPED OR POURED. SPOTTY IF
BRUSHED
JUNE PERRY
VERY GOOD RASPBERRY
-----------------------------------
Calculations by GlazeMasterT
www.masteringglazes.com
------------------------------------
Randy
English Setters
members.tripod.com/~McCallJ/MCCALL2.html
Cotton Patch Pottery
members.tripod.com/~McCallJ/index.html
John Hesselberth on fri 12 sep 08
On Sep 11, 2008, at 9:08 AM, Randy McCall wrote:
> . Are there limits
> in chrome that can be used in chrome red glazes. This glaze will
> turn a
> splochy white where thin and must be put on a even thick.
Hi Randy,
While 0.5% chromium oxide seems to be an upper limit on getting red
from chrome/tin pinks (with 0.2% being more typical), the color is
also strongly influenced by the base glaze composition. A fairly high
level of calcium is required, but I am also convinced, from the
experimenting I have done, that there are some undefined trace
materials necessary. The result is that every time you change batches
of one of the key ingredients you may get a significant color shift.
That is why Ron and I chose to source the boron from a frit instead
of from Gerstley Borate which can be so variable.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
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