Karl P. Platt on tue 22 oct 96
Drakenfeld no longer exists except as a fond memory. I forget the
sequence of events, but Drakenfeld once was an autonomous firm with a
single plant in Washington, PA. Somehow they then got involved with
Hercules Powders which was subsequently aquired by Ciby-Geigy.
Ciba-Geigy bought Hercules for reasons having nothing to do with the
ceramic business and a year or so ago sold off the Drakenfeld Colors
Division in what became Cerdec. Cerdec is a conglomeration of what was
Drakenfeld and what was Dugussa. Both of its original firms have/had
features that made good sense to put together.
The movement in the colors industry has been to combine firms that make
colors and frits with frims that deal with fire-on metals -- "bright
gold" and the like. Drakenfeld-Degussa is not the only example of this.
Engelhardt was doing projects together with what used to be O. Hommel.
Then there's Johnson Matthey, one of the world's largest precious metals
operators and its whole ceramic colors division.
Why has all of this occured? Call it globaloney, globalization, etc. It
helps to understand that a principal consumer of ceramic pigment and
fired-on metals is the automobile industry. Ever see that black band
around the edge of newer windshields ( ceramic pigment) or rear window
defrosters (fire-on metal)? There you have it. Also among all of this is
the fact that the ceramic trade consumes both pigments and
organometallics, too.
The trend is to offer one-stop shopping.
With that out of the way, understand that there are a strictly limited
and very well defined group of materials that comprise ceramic pigments.
Zr-V yellow is Zr-V yellow, regardless of who makes it. Likewise for any
other ceramic pigment (stain) available. This is not to suggest that all
are made equal or that they are similar. There are definite differences.
These can relate to processing, the balance of the composition,
diluents, mineralizers and so on. This is especially true in the more
complex mixtures.
The old Pemco GS-514, a Cr,Fe,Zn stain, unlike almost any of its kin by
other makers, except Mason's Saturn Orange, could be pushed to make a
lovely burnt orange in a glaze loaded-up with ZnO.
A lot of dog stains have been ditched along the way, too. Here I think
of Ferro 10134 which was either brown or purple and always a lot of
matching work during a lot change. I ran into several instances where it
was impossible and bagged the 10134 for a blend of stains furnished by
Drakenfeld.
All glaze firms, while presuming to furnish the best of everything,
actually furnish certain colors which are truly better than anyone
else's. I would take Mason's Cr-Sn pinks and Victoria Green over
anyone's. Cerdec's Zr colors are the purest in my view and Matthey's
CdSSe fritted glazes are by far the most stable in firing.
Also, it is not unusual for stainmakers to expand their offerings by
blending several of their staple offerings. This would make it appear
that there are more types of ceramic pigment than there are.
It would be a useful exersize if the university folks would incorporate
stainmaking as part of their program. These materials are too much taken
for granted.
I believe that red pigments remain the holy grail of the stainmaker.
Much has been made of the encapsulated stains being offered, however, I
still find them to be very far removed from the purity of color had with
the non-encapsulated version of CdSSe pigments. There is a clear
technical reason for this. As the pigment is encapsulated in a litle
ZrO2 husk, and in that ZrO2 has a high index of refraction, any light
going through it is bent pretty hard and any light coming out is
likewise bent. Moreover, the light is also diffused. While the intent is
to derive a 4-color style facility for printing on ceramic tableware,
and progress has been made, the success of this initiative is still a
way off. I saw a souveneir plate last week from the recent SGCD meeting
which used this technology and it was quite nice -- except for the reds.
The encapsulated stains do not represent a new class of pigments, but a
new technology for stabilizing a class of well known pigments. There are
other means, too. However, meeting leaching standards for tableware by
these approaches is difficult -- but withstanding the environs of
Manhattan's subways is well within reach and one hopes that no-one
iseating off of subway platforms -- -but then we are discussing New
York. Who knows?
Anyway, the idea of 4-colorprinting with glaze or enamel goes off into
another whole topic as to why, for example, mixing Co-Si blue and Zr-Vn
yellow don't arrive at leaf greens-- chartreuse, no problem.
See Parmelee for general stain information or Dick Eppler's synopsis of
ceramic stain classification that appeared in the Ceramic Bulletin in, I
believe, 1983. Essentially nothing has changed since that time except
who's doing the classifying.
KPP
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