Alisa Clausen on wed 27 feb 08
Hi Clayart
Paul was looking for purples from Manganese.
I would like to see what influence on color different fluxes in the same
base will make.
I chose two bases, with a fairly high amount of Feldspar, and subbed out the
the Alkaline Feldspar with either gram for gram amounts of other Alkaline
Feldspars or Alkaline Earth fluxes. The numbers for the glazes with new
Alkaline Feldspars (glaze cores) Neph. Syenite,Cornish Stone and Spodumene,
did better over the Alkaline Earth Fluxes, Wollastonite, Talc, Strontium and
Barium.
There were no radical visual differences with the 20% weight change of
ingredients. The glazes were all more or less glossy and translucent. The
most notable change was the addition of Strontium which made rivulets on the
glazes' surfaces. The color responses became more varied with the addition
of 3 Rutile to the 3 Manganese in the base.
Otherwise, the majority of the glazes were a weak to medium brownish pink,
with some slight difference in opacity and opalescence when Rutile was
introduced.
Feldspar subbed OUT in both bases with one each base:
Nepheline Syenite, Spodumene, Talc, Barium, Strontium and Cornish Stone.
Since these bases each have a 20% weight of Feldspar, I thought the
substitution would have a profound and obvious change of the look of the
glaze. They have differences, some ever so slight. When also looking at
the glazes in Glaze Master, it was worthwhile noting which of the bases
would need adjustment later due to too low Silica. Since the BJ base is
already low, none of them where between 3-4. Some of the 20 x 5 did much
better. The rest of the numbers can be seen on the individual base's
analysis in a separate post.
20 x 5 Base Si 3.57 Glossy, translucent
20 x 5 Neph. Sye Si 3.34 Glossy, translucent, very
glassy
20 x 5 Spodumene Si 3.38 Glossy, translucent
20 x 5 Talc Si 2.28 Glossy, slightly opaque
20 x Barium Si 2.27 Glossy, translucent
20 x 5 Strontium Si 2.08 Glossy, translucent,
rivulets in surface
20 x 5 Cornish Stone Si 3.67 Glossy, translucent
BJ Base Si 2.41 Glossy, translucent
BJ Base Neph. Sye. Si 2.32 Glossy, translucent
BJ Base Spodumene Si 2.39 Glossy, translucent, very glassy
BJ Base Talc Si 1.65 Glossy, slightly opaque
BJ Base Barium Si 1.52 Glossy, translucent, fluid
to running
BJ Base Strontium Si 1.40 Glossy, translucent, rivulets
in surface
BJ Base Cornish Stone Si 2.55
These are the tests I made. Because they all were a shade of brownish pink,
and the Rutile additions had many with opalescence, I think it is not
worthwhile describing all of nuances, , but better to look at them at
http://www.flickr.com/photos/glazes/sets/
1. BJ minus Feldspar plus Strontium , ADD 3 Manganese
1a. plus 3 Rutile
2. 20 x 5 minus Feldspar plus Strontium, ADD 3 Manganese
2a plus 3 Rutile
3. BJ. minus Feldspar plus Spodumene, ADD 3 Manganese
3a plus 3 Rutile
4. 20 x 4 minus Feldspar plus Spodumene, ADD 3 Manganese
4a plus 3 Rutile
5. BJ minus Feldspar plus Nepheline Syenite, ADD 3 Manganese
5a plus 3 Rutile
6. 20 x 5 minus Feldspar plus Nepheline Syenite, ADD 3 Manganese
6a plus 3 Rutile
7. BJ minus Feldspar plus Talc , ADD 3 Manganese
7a plus 3 Rutile
8. 20 x 5 minus Feldspar plus Talc, ADD 3 Manganese
8a plus 3 Rutile
9. BJ Base ADD 3 Manganese
9a plus 3 Rutile
10. 20 x 5 Base, ADD 3 Manganese
10a plus 3 Rutile
11. BJ minus Feldspar plus Barium ADD 3 Manganese
11a plus 3 Rutile
12. 20 x 5 minus Feldspar plus Barium, ADD Barium
12a plus 3 Rutile
13. BJ minus Feldspar plus Wollastonite, ADD 3 Manganese
13a plus 3 Rutile
14. 20 x 5 minus Feldspar plus Cornish Stone, ADD 3 Manganese
14a plus 3 Rutile
15. BJ minus Feldspar plus Cornish Stone, ADD 3 Manganese
15a plus 3 Rutile
There are also a couple of bases I tested with 3 Manganese because they were
there on the glaze deck.
I think after looking at all of these tests, I would would not hesitate to
speculate that some Cobalt is needed to get a deep purple. However, I was
curious to see if I would get one, with only Manganese. It appears that
Manganese is very willing to yield a pinkish brownish color, but not deep
purple by itself. That is what I have seen from these many tests.
May Luk writes that she read in "Understanding Glazes (Eppler and Obstler)
that "the Manganese-alumina pink conundrum is similar in color (as Chrome
tin pink) and (thermal) stability, but with improved purity. A zinc-free
glaze, high in alumina, is required"
If we look at the Alum. in these bases,
20x5 Base Al 0.41
20x5 Barium Al 0.24
20x5 Neph Sye Al 0.43
20x5 Spodumene Al 0.45
20x5 Strontium Al 0.22
20x5 Talc Al 0.20
20x5 Cornish Stone Al 0.41
BJ Base Al 0.26
BJ Barium Al 0.13
BJ Cornish Stone Al 0.25
BJ Neph. Sye Al 0.28
BJ Spodumene AL 0.29
BJ Talc Al 0.11
BJ Strontium Al 0.12
there are not too many with high Al, or close or over 0.45.
The 20x5 Spodumene, Neph. Sye and Cornish Stone all yielded
about the same intensity brownish pink as the others.
OK
Paul, I think you need some Cobalt!
Best regards,
Alisa in Denmark
Paul Gruner on wed 27 feb 08
Wow Alisa, that's a lot of glazes. Thanks for all the work you did. I ran
some tests also, posted a thread and put some pictures on flickr:
http://www.flickr.com/photos/23565917@N05/sets/72157603990709468/
We tried different approaches - you started with base glazes that work,
then made some substitutions. I picked one or two fluxes and tried to make
a base glaze with as much of those fluxes as possible. So your glazes all
turned out well and some of mine didn't. But that's OK; as an experiment
it's interesting to see the variations.
I had the impression that too much calcium bleached out the color, but
your tests show pretty consistent color no matter how much calcium is
present. Maybe I was wrong - maybe it was the boron that bleached out the
color.
Anyway, you're definitely right about needing cobalt.
Regarding the other tests you just posted, the Lana Metallic Black and the
Dolita Licorice sure look purple to me. Or do I just have purple on the
brain now?
Anyway, Thanks again for the painstaking research. I really appreciate it.
-Paul Gruner
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