It seems my local supplier only sells Spectralux Opacifier which runs about 60% more than straight Zircopax.  It is the same percentage of zirconium as zircopax. While it seems to have a smaller particle size I can't find anything else that suggests it is better.  Anyone used it and have an opinion?

I am trying the Mastering Cone 6 recipe for Cone 6 Majolica.  Would appreciate any feedback others might have on this glaze.

In addition, Ron Roy has been kind enough to supply me with some reformulations of his recipes in his book to account for the decreased potash content of Custer Feldspar and the fact that G-200 is unavailable in my area.  I'm testing these now.  The Custer reformulations worked well but the Minspar versions underfired during the test and did not produce the proper colors so I have to rerun those tests.

Views: 521

Reply to This

Replies to This Discussion

"Zircopax, ZrSiO4 is a brand name for various grades of zirconium silicate opacifier. The grade that Continental Clay offers is Zircopax-Plus and it is comprised of 94.0% ZrSiO4 on average.

Zircopax Plus is white in appearance and white to grey-white as an opacifier after firing.
As a sole opacifier zircopax is added to glaze and glass formulations in amounts that range from 3% to 12%.
If background opacity is the objective and other colorants are to be included, the use of Superpax rather than Zircopax is often recommended as an overall cost saving measure."

I have not found "Zircopax" for years. It's always been Zircopax-plus, Superpax, or something else. Tony at notes that Zirconium prices have been moving sharply upward, which may be part of the high price you have found. See for more info and the particle size issue.

Thanks George.  I finally found an analysis of Spectralux.  My local ceramic supply (Trinity Ceramics) supplies the potter trade and the commercial trade for hundreds of miles around.  So I think what they carry is heavily influenced by their commercial customers.  They can't explain why they carry it versus Zircopax Plus, Superpax or other versions.

I noticed the proportions of ZrO2 and SiO2 and particle size (1.4 microns) are pretty similar to what insight live shows for Zircopax. (just 50% more expensive).  Anyway I am using it 1:1 for Zircopax in my formulas

Properties of Continental Mineral Processing Spectralux Opacifier (ZrSiO4)
Typical Chemical Analysis (in weight %)
*ZrO2 Zirconium Oxide 65% Min.
SiO2 Silicone Dioxide 32.5% Typ.
AI2O3 Aluminum Oxide 2.0% Max.
TiO2 Titanium Dioxide

0.35% Max.

Fe2O3 Iron Oxide 0.15% Max.
U & Th Uranium & Thorium 475 Max.
P2O5 Phosphrus Pentoxide 0.09% Typ.
*Includes 1-4% Hafnium Oxide HfO2

Reply to Discussion



  • Add Videos
  • View All

Use These Links to Support Us

Low cost flat lapping disc can be used on you potters wheel if you, drill bat pin holes in it, and provide a trickle of water to cool it. At, 120 grit for aggressive material removal. Click the image to purchase 

Members have had great things to say about John Britt's new book, Mid-Range Glazes. Click the image to buy from

Purchase Glazes Cone 6 by Michael Bailey, The Potters Book of Glaze Recipes by Emmanuel Cooper, or Making Marks by Robin Hopper, all available at amazon.comMastering Cone 6 Glazes by John Hesselberth & Ron Roy is now out of print.

Harbor Freight is a great place to find unbeatable prices for better HVLP spray guns with stainless steel parts and serviceable economy models, as well as detail guns, all tested by our members for spraying glazes, as well as compressors to power the guns. As yet no one has tested and commented on the remarkably inexpensive air brushes at harbor freight.

The critter siphon gun is a spray alternative that is well liked by some of our members, and is available at amazon.

Amazon is also a competitive source for photo light tents for shooting professional quality pictures of your work. They also have the EZ Cube brand favored by several of our members. You might also want to purchase the book Photographing Arts, Crafts and Collectibles . . .

If you are up to creating videos of your work or techniques you might want to invest in a flip video camera

Following are a few scales useful for potters. Your final price could be less or more - things change.

American Weigh Black Blade Digital Scale, 1000g X 0.1g $11.08 

For the non-digitally inclined the old standard Ohaus Triple Pro Mechanical Triple Beam Balance, 2610g x 0.1g, with Tare $169.00

And finally a low cost clone of the OHaus. The Adam Equipment TBB2610T Triple Beam Mechanical Balance With Tare Beam $99.62

ebay is a great alternative for many tools and the equipment used in the ceramics studio - kilns, wheels, extruders, slab rollers are often listed there both new and used.

Tips for Members

If you just want to spout off, it is best accomplished as a blog posting. If you want to get more guidance and ideas from other members, ask a question as a new discussion topic. In the upper right corner of the lists for both types of posting, you will find an "+Add " button. Clicking it will open an editor where you create your posting. 4/16/2014

© 2021   Created by George Lewter.   Powered by

Badges  |  Report an Issue  |  Terms of Service