Wiseman Ceramics

The first time I saw a matte crystalline glaze was on a piece by Hein Severijns. Both the bottle and the glaze recipe were spotlighted in the book, “Smashing Glazes”, by Professor Susan Peterson. Neither the recipe, nor the corresponding firing schedule looked easy.
It was only a short time later, when John Tilton’s crystalline mattes caught my eye.
Tilton has told me many times how troublesome these glazes are to produce (refer to the relevant Clay Times Article), but those that come out well are extraordinary.

In 2006, while preparing for the Peter Ilsley Workshop, Ilsley referred to the glaze developed by Peter Fröhlich. The glaze recipe is listed in Ilsley’s book, “Macro-Crystalline Glazes”:

Matt - 1260°C
Frit 4067 : 77
Feldspar Potash: 21
Zinc Oxide: 16
Lead bisilicate: 11
Flint: 7
Rutile: 8

The 4067 frit is manufactured by Mondre & Manz in Germany. It is only one of the frits that host Kris Friedrich had shipped in for the Ilsley Workshop.
At the workshop, John Tilton, Marsha Silverman, and Mark & Scott Winner focused on developing Fröhlich’s recipe, with good success.

The chemical formula for MM 4067 is:

K2O: 4.60
ZnO: 12.00
BaO: 37.80
Pb2O3: 11.00
Al2O3: 5.00
SiO2: 29.60

Although MM frit 4067 is not available in North America, a number of people are still experimenting, either by using the frit directly or by substitution. Chris Cantello has discussed some ideas on this site (see the comments section at the bottom of the Ilsley workshop page).

Andreas Widhalm created a frit replacement through a computer program he developed, employing the Seger Method:

Potash Feldspar: 24.411
Lead Mono-silicate: 12.649
Zinc Oxide (Calcined): 10.917
Barium Carbonate: 43.947
325 mesh Silica: 8.077

Bill Campbell has been firing some gorgeous matte crystallines. It employs neither the MM 4067, nor the additional Lead component called for in Fröhlich’s matte recipe.

As for myself, I am working with a glaze (and a process) that doesn’t rely on lead or the German frit as well.
This matte/satin-matte effect is achieved by a combination of chemically altering the base glaze, putting it through a standard crystalline firing, and then re-firing it to just below it’s melting point. It’s tricky, as firing it even a bit hotter than necessary will cause the glaze to soften too much and produce a blistered surface. Glazes fired in this way without the chemical modifications may provide a similar effect, but the loss rate is higher, due to an even smaller heatwork window. A piece must often be put through several firings before it yields the right surface –but once it blisters, it’s ruined.
Needless to say, at this point I’m doing very few of these.

Back to Crystalline Events Page

In May of 2006, Peter Ilsley, author of “Macro-Crystalline Glazes” led an extensively hands-on workshop at Friedrich Pottery in Palm Springs, California. I was happy to assist Mr. Ilsley and the event host, Kris Friedrich, along with John Tilton, Tom Wallick, and Glenn Doyle.

Twenty-five crystalline artists were able to glaze their own bisqued work, and have the pieces fired in their choice of 6 kilns (4 computer electrics, one post-fire reduction, and one computerized auto-damper gas kiln). These kilns were often fired simultaneously, resulting in at least 2 kiln openings a day for 5 days straight. As a result, the group was able to compare oxidation to reduction on several gloss crystalline glazes as well as some matte crystalline recipes made from special frits that were ordered in for the event.

For the glossy crystallines, frits GF-106 and Ferro3110 were used to make up various bases. As GF-106 recently became unavailable, Laguna Clay Company’s Clay Manager, Jon Pacini brought a sample of a substitute for Gloster’s GF-106 frit called F413. John Tilton and Marsha Silverman focused on the German frit (Mondre & Manz 4067) that Kris had shipped in, hoping to expand on the efforts of European crystalline artist Peter Frohlich.

Aside from lecturing, Peter Ilsley took charge of the on-site “top-hat” raku kiln, and performed post-fire reduction on any oxidation fired pieces we felt would benefit. I was able to put in several tests with silver nitrate. What resulted from the silver tests were pots that look like they were formed out of sterling silver or gold.

While preparing for this event, Peter told me that he had been wanting to have a favorite frit made, Degussa’s 90208M, since it had been out of production for many years. This yielded a wonderful outcome… further details here.

Paul Geil paid a visit during the final days of the workshop to unveil the new Geil JH10 prototype.

A very special thank you to Kris (and Marilee) Friedrich for having us in their home and hosting an incredible event, and of course to Peter Ilsley for offering his years of experience!

Related Links:
Clay Times Article: “Crystalline Glaze Workshops 2005-2006″

Ceramics Monthly “Kris Friedrich Crystalline Glaze Workshop”

The Story of Five Popular Crystalline Glaze Frits

Matte Crystalline Glaze - Focus: Mondre & Manz 4067 Frit

Here’s the Silver Nitrate recipe published in Clay Times Nov/Dec, 2006:

Fusion Frit 75: 51.5
Zinc Oxide: 23.5
Silica: 22.0
Grolleg: 1.0
Calcined Alumina: 2.0

Add:

Titanium Dioxide: 4.0%
Silver Nitrate: 5.0%
Cobalt Carbonate: 0.5%
MAGMA Binder: 0.3%

I have since stopped using Silver Nitrate. You can read more at the post: Using Silver (Ag) as a colorant in a ceramic glaze.

This piece is a heavily reduced Silver Nitrate and Cobalt glaze. Upon my return, I accented it with a low-fire enamel and antiqued gold leaf. The image barely shows it, but the crystals actually have soft streaks of red, purple,and blue.

The pedestal was glazed with black gloss and crackle glazes alternating within the successive rings. Gold leaf and low-fire glass enamels decorate it as well.