Autumn Downey on thu 28 nov 96
I haven't easily found any information on how zircopax and Superpax compare.
Are there any major differences in opacity, or melting properties and
chemical formulas? So far, we have only used zircopax, so I haven't had
direct experience with superpax, but was wondering if it might be a bit
smoother.
Thanks for any info.
Autumn Downey
downeya@internorth.com
Yellowknife, NWT, Canada
Craig Martell on fri 29 nov 96
Hi: Request technical info on both materials from your supplier. If they
don't have any info they should be willing to get it for you from the
manufacturer. I use Ultrox as an oppacifier when I can't use Tin Ox. It
works well, you might want to look into it. Also, check the Ceramics Web,
lots of good info there. I haven't checked the Web for opacifiers though.
Kind Regards, Craig Martell-Oregon
"Rafael Molina-Rodriguez (Rafael Molina-Rodriguez)" on sat 30 nov 96
Autumn :
I concur with Craig's view of Ultrox as an opacifier. I use it almost
exclusively in the glazes I work with. On occasion I use it, as Craig
does, with Tin Oxide. This is the case with Arbuckle's white majolica
base.
In all of the years I've been working in clay (sixteen), I don't believe I've
ever used any other opacifier. If the recipe calls for Zircopax or
Superpax I just substitute the same amount of Ultrox. Good luck!
Rafael
rmr3431@dcccd.edu
>>> Autumn Downey 11/28/96 09:55am >>>
----------------------------Original message----------------------------
I haven't easily found any information on how zircopax and Superpax
compare.
Are there any major differences in opacity, or melting properties and
chemical formulas? So far, we have only used zircopax, so I haven't
had
direct experience with superpax, but was wondering if it might be a bit
smoother.
Thanks for any info.
Autumn Downey
downeya@internorth.com
Yellowknife, NWT, Canada
Tony Hansen on sat 30 nov 96
Here's what I have on the three opacifiers under discussion:
FORESIGHT Material Database Report
==================================
MATERIAL: ULTROX - ZIRCONIUM SILICATE GLAZE OPACIFIER
DATE: 06/17/96
SUPPLIER: M & T CHEMICAL
FAMILY: OPACIFIER
RAW WEIGHT: 100.00
ANALYSIS & UNITY FORMULA
========================
ZrO2...... 65.00% 0.53
SiO2...... 35.00% 0.58
======
100.00
Three types are available: Ultrox, Ultrox 500W, Ultrox 1000W.
Ultrox opacifiers are claimed to assure uniformity of glaze opacity,
texture and color over a wide range of temperatures and compositions. They
reduce the expansion of glazes and tend to reduce crazing. They increase
the resistance of glazes to chemical attack and widen the firing range.
Ultrox melts at 4000F and has a coefficient of thermal expansion of 42 x
10-7, a hardness of 7.5 Moh and index of refraction of 2. It is composed of
65% ZrO2 and 35% SiO2 in a formula of ZrO2:SiO2.
Ultrox is used for the production of both white and color glazes for
sanitary ware, wall tile, glazed brick, structural tile, stoneware,
dinnerware and special porcelains. It is used in amount of 12-20% of the
glaze batch.
-Ultrox has an average particle size of 2 microns.
-Ultrox 500W has an average particle size of 1 micron and thus provides
greater whitening power. It lightens color appreciably and thus requires
more stain.
-Ultrox 1000W has an average particle size of .5 micron and provides the
maxium reflectance and opacity.
Ultrox has an extremely high melting point and low uniform thermal
expansion and can thus be slip cast or pressed to produce zirconium
silicate refractories (for use in glass melting furnaces, foundries,
refractory porcelains, washes for refractory slabs, refractory cements).
Compositions of Ultrox alone can approach the theoretical density of
zircon.
Liquidous temperature: 4000F
Coefficient of thermal expansion: 42 x 10 -7
Hardness: 7.5 Moh's scale
Index of refraction: 2
MATERIAL: ZIRCOPAX - ZIRCONIUM SILICATE
DATE: 06/17/96
SUPPLIER: TAM
COST: 168.65 per 50BG
FAMILY: OPACIFIER
RAW WEIGHT: 183.30
ANALYSIS & UNITY FORMULA
========================
ZrO2...... 67.21% [ 1.00]
SiO2...... 32.79% 1.00
======
100.00
(See also ZrO2 oxide, Zirconium silicate)
Zirconium is extremely stable and will survive to temperatures above 4000
degrees F. Up to 20% may be required to opacify the average transparent
glaze and amounts beyond this reach saturation where crystallization begins
to occur. The exact amount needed varies between different glaze types.
Zircopax is often used for semi-opaqueness, finer materials being used for
full opacity.
Zircon has a low expansion, so it will tend to reduce crazing. In addition,
it will produce a more viscous melt, which means that crawling and
pinholing could occur in glazes which have a lot of zircon. These problems
can normally be solved by cooling slower and taking measures to get a
better bond between raw glaze and body during application.
In North America, the most popular zirconium opacifiers are made by TAM,
and fall under the brand names of Zircopax, Superpax and Excelopax. These
vary according to particle size, the finer the size, the better
opacification achieved. In addition, the finer sized material contain a
little extra silica for maximum whiteness.
Typical Properties:
Formula: ZrSio4 Weight: 183.1
Linear Coefficient of Expansion:
-25-700C cm/cm/degreeC 42 x 10 -7
Specific gravity: 4.5
Particle Size: Zircopax Superpax Excelopax
Microns, Ave. 1.3 .74 .55
Bulk density lbs/cu ft 100 75 75
Surface area, m2/g 4.5 9.8 12.8
PROPERTIES
----------
Zirconium silicates are used primarily as opacifiers in glazes at all
temperatures. Although tin oxide is more effective, zirconium
materials are much cheaper and are more stable in reduction and less
reactive with some colorants (i.e. chrome). Although zirconium oxide
is effective as an opacifier, zirconium silicates disperse better and
are cheaper where the glaze can tolerate or be reformulated to
tolerate the added silica.
MATERIAL: SUPERPAX - ZIRCONIUM SILICATE OPACIFIER
DATE: 06/17/96
SUPPLIER: TAM
FAMILY: OPACIFIER
RAW WEIGHT: 92.10
ANALYSIS & UNITY FORMULA
========================
ZrO2...... 61.06% 0.50
SiO2...... 31.04% 0.52
======
92.10
Zirconium Silicate opacifier (see Zircopax).
Superpax is a very fine grade zirconium silicate opacifier and will
produce a whiter result than less expensive grades. See Zircopax.
=======================================================================
Tony Hansen, IMC - http://digitalfire.com
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