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how meaningful are eutectics?

updated sun 11 feb 07


karen gringhuis on thu 8 feb 07

Lili -

>To simple minds eutectics seem magical--i.e. I think
them so-- but I wonder how much use they are to

Very useful in that, as you say, they can make magical
things happen. Or just the opposite. How useful is a
broader understanding of them to potters? Different

As Hamer says "the fact that this sort of reaction can
occur can throw some light on otherwise inexplicable
behavior in a glaze." Hear loud and clear his point of
"very difficult to establish." He means it. There are
books and books filled with data tables on possible
ingredient combinations.

>Can one actually say more?<

Not really. You've pretty well got it. A lot of
technical info well understood is indeed very useful
to potters but IMHO, detailed knowledge of eutectics
is not.

Karen Gringhuis
KG Pottery
Box 607 Alfred NY 14802

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Ivor and Olive Lewis on sat 10 feb 07

Dear Clayart Friends,

Perhaps it would help those who are forming an interest in this topic to =
have a wider view of things.

In searching for material about this topic I received the following =
reply from Bill Opperman of OSU* recently. This gives me a chance to =
acknowledge his help.

<in our library collections or the University Archives (In fact, we have =
none of his material in the archives.) He was the chair of the =
Mineralogy Department here at Ohio State University from 1913-1952. We =
have considered the publications that looked like they might be on the =
same topic but have no go candidates for your search.>> Prof. W.J. =
McCaughey drew a distinction between what happens when a melt is cooled =
and what happens when a mixed powder is heated. With the passage of time =
this distinction has been lost or disregarded, though it emerges in the =
writing of Hutchinson Cuff.

Below is a summary of some of many statements that have been published =
in recent years.

I hope some of you find them interesting !

Eutectics in Ceramic Systems.

Some definitions and opinions

"eutectic mixture A solid solution of two or more substances having the =
lowest freezing point of all possible mixtures of the components"

E,B Urarvov, Alan Isaacs. "The Penguin Dictionary of Science" Page 124, =
6 th Edition 1986.

"eutectic point Two or more substances capable of forming a solid =
solution with each having the property of lowering each other=92s =
freezing point ; the minimum freezing point attainable, corresponding to =
the eutectic mixture is the is the eutectic point."=20

E,B Urarvov, Alan Isaacs. "The Penguin Dictionary of Science" Page 124, =
6 th Edition 1986.

"The point at which the greatest degree of melt occurs is known as the =
eutectic point" E. Cooper and D. Royle, "Glazes for the Studio Potter". =
Page 18. 1978

"When a second component is added to a pure material, the freezing point =
is often lowered"

Kingery et al. " Introduction to Ceramics". Page 284. 1976

"The eutectic temperature is the temperature at which the liquidus =
curves intersect and is the lowest temperature at which liquid occurs"

Kingery et al. Page 284

"The eutectic composition is the composition of the liquid at this =
temperature, the liquid coexisting with two solid phases"

Kingery et al.

"....a mixture containing 5.5% alumina and 94.5% Silica melts at 1,549 =
deg C. This is the lowest combination of the two compounds, and is =
called an eutectic composition. The melting point of this mixture is =
called the eutectic temperature...."

Exford Newcomb, Jr, "Ceramic Whitewares. History, technology and =
Application. Page 37. 1947

"In order to attain the maximum effect, eutectic mixtures must be =
reduced to a homogeneous mass. Mere mixing of the raw materials even =
though they are finely ground together for a long time will not give the =
necessary molecular dispersion obtained by fusion"

C. W. Parmellee. "Ceramic Glazes". Page 92, 1 St Edition 1948.

"When two or more materials are mixed together it is found that there is =
one mixture which melts at a lower temperature than any other. This is =
called the "eutectic=92 mixture (Greek: t=EBctos, molten).

M. Cardew, " Pioneer Pottery" . Footnote p 50, Reprint 1977.

"The proportion of two oxides which has the lowest melting point is =
called the eutectic."

D. Rhodes. "Clay and Glazes for the Potter" Page 162, 2 Nd Edition, =
Reprint 1979

" A eutectic is the lowest melting point of two or more materials when =
blended together"

G. Daly. "Glazes and Glazing Techniques" Page 9 , 1995

"...certain elements, such for example as magnesium and silica, combine =
in definite proportions as the first opportunity in a rising =
temperature. Such a combination is called a eutectic, and only what is =
left over will harden or soften the glaze."

B. Leach, "A Potter=92s Book". 2 Nd Edition 1945, reprint, 1967.

"At the eutectic temperature both minerals crystallise simultaneously =
until all the magma has disappeared"

Y. Hutchinson Cuff, "Ceramic Technology for Potter=92s and Sculptors". =
Page 28-9, 1996

=91A eutectic composition is the particular combination of two or more =
materials in a simple system that melts at the lowest possible =
temperature of a mixture of those materials."

Y. Hutchinson Cuff. Page 265, 1996

"EUTECTIC POINT: The point at which two or more materials together melt =
lower than either one separately."

Susan Peterson. "The Craft and Art of Clay" P 380, 1992

"EUTECTIC POINT: That mixture of two or more substances which has the =
lowest melting point of the whole series".

Robert Fournier, "Illustrated Dictionary of Practical Pottery". Page 79, =

"Eutectic: A eutectic represents an invariant (unique temperature, =
pressure . composition) point for a system at which the phase reactions =
on the addition or removal of heat resulting and increase of decrease, =
respectively. Of the proportion of liquid to solid phases."

E. M. Levine et al. "Phase Diagrams for Ceramists" Page 6, 1964

"Eutectic mixture. The proportional mixture of two or more substances =
which melts at the lowest possible temperature. This temperature is =
called the eutectic point."

F. Hamer. "The Potter=92s Dictionary of Materials and Techniques" Page =
114, 1975

"The first is the eutectic reaction in which a liquid becomes saturated =
with respect to the end members such that at the eutectic temperature =
two solids precipitate out of the liquid simultaneously."

M. Barsoum. "Fundamentals of Ceramics". Page 276, 1997

"....and will, therefore, contain some calcium, which is prone to form a =
wide range of eutectic melts with many materials that are generally =
quite fluid."

De Boos et al. "Handbook for Australian Potters" Page 9, 1984

"eutectic mixture A solid solution consisting of two or more substances =
and having the lowest freezing point of any possible mixture of these =
components. The minimum freezing point for a set of components is called =
the eutectic point."

Oxford concise Science Dictionary. Page 226, 3 rd Edition, 1996

"The eutectic is a mixture and not a chemical compound, although often =
(for example, in eutectics formed from one metal in another the =
crystals of solute and solvent are so fine grained, that the two =
constituents can be seen only with the aid of a powerful microscope."=20

P. J. Durrant. "General and Inorganic Chemistry" Page 159, 2.Nd Edition =

"The formation of eutectics (i.e. mixtures which have a fusion =
temperature lower than that of any of their constituents), gradually =
take place and with the development of a liquid phase, the more =
refractory particles are surrounded and taken into solution in the =
liquid phase."

Harry Fraser. "Glazes for the Craft Potter". Page 13, 1998 (First =
published 1973)

"eutectic. The lowest melting point of the mixture of materials compose =
a glaze. This is always lower than the melting points of the individual =

Glen C. Nelson "Ceramics, a potter=92s handbook" Page 201, 3 rd Edition =