LETTERS TO THE EDITORS
Tempest in a Porcelain Teapot
To the Editors:
The account of Europe's reinvention of porcelain in Roald Hoffmann's
"Meissen Chemistry" (July-August) reflects the confusion
in Janet Gleeson's The Arcanum. Reproducing Ming chinaware
using the original ingredients took longer to commercialize than she
suggests. Georgian and Victorian "china" makers from Spode
to Sevres fudged by adding extra and easier fluxes like bone ash and
gypsum. Mullite is a product of the porcelain process, not a
starting material, and the "fine needle-like crystals of
mullite" in china are not "cemented by glassy
silica." Mullite crystals grow out of a complex silicate
melt—porcelain kilns never attain pure silica's melting point.
Despite Frederic Bottger's deserved fame as the first master of
Meissen decor, the cake comes before the icing. The statuette the
article captions as "made in Bottger's red stoneware around
1714 " exemplifies instead the first true mullite porcelain
created by his mentor, Count Tschirnhaus around 1704. The white
medallions presented as the first European porcelain are indeed
Bottger's , but they're not "porcelain," but an alabaster
fluxed ceramic in which wollastonite (a silicate of calcium)
replaces mullite.
As Colbert's protege, Tschirnhaus got short shrift from East German
historians, but his nascent materials research lab spun off the
equations for caustic curves, solar furnace mirrors the size of the
Hubble primary, and giant burning glass lenses subsequently used by Lavoisier.
Porcelain depicted as an alchemical Holy Grail makes a great yarn,
but Bottger was no alchemist's apprentice. His master was a Prussian
apothecary, and Bottger arrived in Dresden fleeing a murder warrant
for poisoning him. To add to the potential for more porcelain
potboilers, Bottger, ennobled after Tschirnhaus's convenient death,
was caught fleeing Meissen for Vienna.
Russell Seitz
Watertown, Massachusetts
Dr. Hoffman responds:
Dr. Seitz makes a valid point by emphasizing that von Tschirnhaus's
contribution to the imitation of Chinese porcelain in Europe was
more important than I made it out to be. What a great scientist and
technologist he was.
However, I don't think I was far off on the materials science, as
complicated as it is, of the early European porcelains. What I have
learned from work of Vandiver and Kingery is that when one analyzes
"porcelain," one finds quartz, mullite and glass. The
mullite is cemented together by a glassy matrix. Dr. Vandiver says
that she has seen no evidence that the Meissen porcelain contained
bone ash or gypsum, or that extra fluxes were added. Later imitators
did produce high temperature ceramics using such fluxes, such as
bone porcelain, like Beleek.
The area surrounding the castle workshop, that might give us further
valuable evidence, has not been excavated. So much still remains to be
done on the history of this remarkable episode in European technological
history!