Sondahl's Crystalline Glaze Color tests

Using my standard crystalline Cone 9-10 base, I tested 5 common colorants, and their combinations.  All the tests included rutile, since some titanium is desirable for seeding the crystals, but by itself it yielded a white background with gold crystals.
These are the recipes:
 
A B C D E
Frit P25 28.4 28.4 28.4 28.4 28.4
ZnO 25.25 25.25 25.25 25.25 25.25
Flint 12.9 12.9 12.9 12.9 12.9
Potash
Feldspar
22.7 22.7 22.7 22.7 22.7
Whiting 3.1 3.1 3.1 3.1 3.1
Kaolin 5 5 5 5 5
Rutile 2 2 2 2 2
CuC 3
CoC 2
Mn02 3
RIO 3

Note: When combining these glaze samples, an equal volume of glaze was added of each.  The resulting glaze thus is diluted to one half of the strength of colorant.
That is, combining B and C above, the recipe would have 1.5 grams CuC and 1.0 grams of CoC (all the ingredients above these two are the same).

When viewing the tiles, consider that glaze application of small tests  inevitably varies.  In general, whether crystals were plentiful or not mostly depended on the thickness of the glaze.  These tests were to show color response more than crystalline growth. They were all fired on the same shelf in the kiln, at the Cone 9-10 range.

In each group of tiles below, the first is the pure colorant represented by the code letter, then the other combinations are shown.
I liked a number of the tests.  Manganese made a lovely warm beige, but I tend to shy away from using it much, partially from the gasses it gives off in firing, which have become a health concern in recent years.



 

H65A H65AB H65AC H65ADH65AE   A=Rutile B=Copper Carb. C=Cobalt Carb.  D=Manganese Diox. E=Red Iron Oxide



H65B  H65BC H65BD H65BE
H65AB    A=Rutile B=Copper Carb. C=Cobalt Carb.  D=Manganese Diox. E=Red Iron Oxide


H65C H65CDH65CE H65BC
H65AC    A=Rutile B=Copper Carb. C=Cobalt Carb.  D=Manganese Diox. E=Red Iron Oxide

H65D  H65DE   H65AD H65BD
H65AD   A=Rutile B=Copper Carb. C=Cobalt Carb.  D=Manganese Diox. E=Red Iron Oxide



H65E   H65AE H65BE H65CE
H65DE   A=Rutile B=Copper Carb. C=Cobalt Carb.  D=Manganese Diox. E=Red Iron Oxide


H65ABC H65BCE  Other multiple combinations were tested, but not impressive.


Part of my goal in doing these tests, which were inspired by Fa Shimbo's similar ones, was to see which colors the crystals would turn in various background glazes.
In all of them there was apparently enough iron from the rutile that gold or brown crystals would form on a lighter background.  Copper tended to stay in the backgound, as did Manganese.Cobalt and Iron appeared to be able to be mixed in the crystals, creating more muted blues than with Cobalt by itself.

Because Copper is a strong flux, some of the tests with Copper ran off the tiles (always a possibility with crystalline glazes).  The Copper tile was the only glaze with some cratering, probably caused by glaze boiling. If you wanted a green glaze, I'd consider dropping the whiting if you're using Copper.

Brad's crystalline primer page
 Brad's Index.