Roeder on mon 24 feb 97
Hello,
I have come across some recipes for cone 6 oxidation glazes that call for D
F Stone, Boroflux #1, and Pyrotrol...all of which are unfamiliar to me.
I've looked in a couple of my clay supply catalogs and don't find these
items. What are they? Are there substitutes? Does anyone know a supplier
that carries them?
TIA
Candice Roeder
Richard Burkett on tue 25 feb 97
>I have come across some recipes for cone 6 oxidation glazes that call for
D
>F Stone, Boroflux #1, and Pyrotrol...all of which are unfamiliar to me.
DF Stone is probably Corwall Stone DF. Boroflux is most likely a standard
boron frit (try Ferro frit 3124), and Pyrotrol is a brand name for a
commercially available material known more commonly pyrophyllite.
Richard Burkett - School of Art, SDSU, San Diego, CA 92182-4805
E-mail: richard.burkett@sdsu.edu <-> Voice mail: (619) 594-6201
Home Page: http://rohan.sdsu.edu/dept/rburkett/www/burkett.html
CeramicsWeb: http://apple.sdsu.edu/ceramicsweb/index.html
Tony Hansen on tue 25 feb 97
BOROFLUX - ZINC BORATE
This material has been promoted in the American Ceramic Society Bulletin
and other journals as one which can reduce energy costs by significantly
lowering the maturing temperature of bodies and glazes with very small
additions.
It is claimed that 2.5% addition of Boroflux #1 can lower firing from 3 to
6 cones, depending on spar content of body. The mechanism of this strength
is not necessarily vitrification, but the glassy binding nature of the
Boroflux in even porous bodies.
Manufacturer is: Climax Performance Materials/Amex Inc, Greenwich, CT 06836
USA
Following are comments by William M Jackson of Climax Performance Minerals:
Firing at cone 9-11 does not produce better results in the product than
firing at cone 01-06. Indeed, at high fires more energy is used which
increases costs. The American ceramic industry, with lower energy costs,
can be more competitive with foreign trade. A lot of energy is required to
melt frits. When frit is sold, it is too coarse for stirred glaze, so a
ball mill must use more energy to grind it. Frits tend to melt or soften at
low temperatures (1000-1300F), which tends to trap gases trying to escape.
The action may form pinholes in the glaze.
On the other hand, glazes made from Boroflux don't melt until they reach
1600-1700F, which allows the gases to escape without forming pinholes.
In 1982 we discovered that 2.5% Boroflux #1 lowered firing from 3 to 6
cones, depending on spar content. The difference in cone reduction occurred
because the body with more fluxes (spar or nepheline syenite) is decreased.
The strength of the fluxed bodies is usually higher than most high-fire
compositions. In fact, the strength of fluxed semivitreous bodies exceeds
the strength of low-fire vitreous bodies.
In tests, a bathroom fixtures body had additives at 2-5% with 18% feldspar
and up to 33% nepheline syenite. The firing was reduced from cone 9 to cone
4 and the glaze looked better. This means that no new glazes are needed, so
a changeover could take place almost overnight and energy savings would
start immediately.
For porcelains, the more Boroflux used, the whiter the fired color becomes.
Typically, 2.5% Boroflux will reduce firing 3-5 cones. The greater the spar
content, the greater the reduction in firing temperature.
Sodium silicate dispersed casting slips tend to thicken with Boroflux, so
for each 1% added, 2% extra water may be needed. Alternate dispersants like
Alcosperse 149-C might also be helpful. A cone 10 porcelain casting slip
can often be reduced to cone 6 with 5% Boroflux.
PYROTROL 2253/3503 - ANDALUSITE/PYROPHYLLITE ORE
ANALYSIS & UNITY FORMULA
========================
KNaO...... 0.40% 0.02
TiO2...... 0.40% 0.02
Al2O3..... 22.00% [ 1.00]
SiO2...... 74.00% 5.71
Fe2O3..... 0.40% 0.01
LOI....... 2.80%
======
100.00
The Pyrotrol group of mineral products offers a controlled blend of milled
Andalusite/Pyrophyllite ores designed to control strinkage in whiteware
ceramic applications. Pyrotrol products impart higher strength in
electrical porcelains and reduce dunting problems associated with
traditional porcelain bodies. Alumina contents are controlled to meet
certain specifications. Pyrotrol produces an excellent kiln car wash and is
an inexpensive coating material for facebrick production.
Bulk Density: 55.0 for 2253, 60.0 for 3503
PCE: 26
Sieve Analysis: #2253 #3503
On 200 mesh: 0.4 -
325 mesh: 8.0 1.0
Analyses are same.
--
=================================================================
Tony Hansen, IMC - Get INSIGHT 5 beta or The Magic of Fire II at
http://digitalfire.com or http://www.ceramicsoftware.com
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