Wiseman Ceramics

I prefer to spray my glazes. When done correctly, this method can create a smooth and very even coating of glaze. This way you don’t wind up looking at the piece after it is fired, wondering whether “that effect/defect” on one side is a result of a heavier or thinner application. Brushing and dipping can certainly be done with accuracy and has it’s own advantages, but spray glazing is still my preference.

When spraying, I place a piece on a banding wheel (I think Shimpo makes the best), and apply each glaze layer to the point where it stops drying… this will be just before it starts to run. I wait until the glaze sets up again (the watery sheen disappears) before spraying the next coat, so as not to distort the surface with the pressure coming out of the gun. But don’t let the layer dry completely, as you risk the first layer(s) bubbling/lifting up off the pot as it rehydrates. This “dry -but not too dry” rule applies to any application method, by the way.

Whether spraying, dipping, or brushing, I test the thickness of my glaze application with a push pin marked in millimeter increments (1-3mm) and record that in my notes. Many people use this method for testing glaze application thickness. The first time I read about this simple technique, was in the book “Ceramic Technology for Potter’s and Sculptor’s” (Cuff, 1996). John Tilton brought a depth gauge (sometimes incorrectly referred to as a micrometer), specially machined for testing glazes, to the Peter Ilsley Workshop in 2006.

Concerning spray guns, I’ve had acceptable results with many types, but I think HVLP works best. I buy these from a place like Harbor Freight, my reason being that paint guns weren’t made to have abrasive glaze particles passing through them. In this regard, I’ve found that more expensive guns wear out just as fast under this type of (ab)use, so I buy the “cheapies” and treat them as disposable (actually, my most recent 3 have lasted over a year).

I also recommend gravity feed models… otherwise, you’ll have glaze left in the canister of the “bottom feeder” models, as they, well… don’t do all that good a job of feeding off the bottom…

Incorporating additives such as suspension agents and binders to enhance the glaze’s storage and dry handling properties is a good idea. Click here for this info.

Crystalline glaze recipes have little to no clay content, so there are problems in terms of settling when stored even for short periods. Cracks that form in the raw dried state can result in non-adhesion and crawling when these glazes are fired. Using binders and suspension agents as additions to the glaze base will help with most of these issues.

I premix my binder/suspender in water so that it is in solution and available when I need it. Refer to the post on: Adding Water, Suspenders, & Binders to a Glaze for more on this process.

I usually prefer combinations of CMC, V-Gum T, and MAGMA as my binder/suspender.
V-gum CER is also a good product, but when using CMC and V-gum T together, I prefer a different ratio.

David Pier designed MAGMA, and I was lucky to get a sample before it officially hit the shelves… it took very little to have an effect, and I liked it right away.

Another friend, John Tilton has recommended calcium nitrate. He uses it to aid in brushing and thinks that within certain conditions, it might aid in spraying as well. Personally, I like a thinner rather than a thicker consistency when spraying, so it would require further testing.

The basic goal with a zinc-silicate crystalline glaze is to create a completely melted solute of Zinc and Silica. This is achieved through flux and heatwork. If one goes down, then the other must go up to compensate; however I do not believe that flux can be directly used as a replacement for heatwork when going after the effects of ^9+ crystalline glazes. You’ll see what I mean when you look at the visual produced at cone 6.
That is not to say that ^6 isn’t a worthwhile endeavor… My feeling is that crystallines produced at lower temperatures should be viewed as an aesthetic all their own.

During the past 2 years, I have been firing within the ^11-12 range. When I first started however, I was limited by the school kiln that would not satisfactorily fire above ^8. I actually ended up firing in the ^6 range, but the experience I gained in the ^7-8 range provided just enough heatwork to get the glaze to look more like the higher fired versions. So if the kiln you have access to can be fired that high, it’s worth exploring.

William Schran’s crystalline glaze testing in the ^6 range is extensive, which is why he was invited to present at LatticeStructures™ 2005 on this subject. His main addition to the glaze as an auxiliary flux is lithium carbonate. I would also suggest experimenting with additions of sodium, as this is one of the most powerful fluxes. Boron is stronger, but most people agree that it can disrupt macro-crystal formation… that being said, try small percentages anyway. To add sodium, try Nepheline Syenite or Kona F-4 Feldspar. Sodium Carbonate can be used as well, but keep in mind that it is a water soluble chemical.
Lithium may have been chosen as it doesn’t encourage the crazing as much as sodium, but there is so little of either that needs to be added to decrease the cone value that it may not matter. Lithium is said to promote brighter colors and encourage crystal growth (the latter is documented only at low-fire temperatures, however).
Schran would have more experience here.

The most valuable information I can offer for anyone attempting to learn an aspect of glaze chemistry is to concentrate on each ingredient. Refer to the post: “Getting Started with Crystalline Glazes“. Here the main focus is flux, zinc, and silica. Endeavors to fire to ^6 are already going to adjust the first, but one would benefit greatly by taking all three components and creating a small 10 cell triaxial or quadraxial graph. Knowing what each part of your glaze base does in greater and lesser amounts, and having a visual record in the form of tests, will help immeasurably in the future.

A basic recipe for a ^9-10 crystalline glaze is >
Ferro Frit 3110: 50%
Calcined Zinc Oxide: 25%
325mesh Silica: 25%

2 good starting points for ^6 are >
1- Ferro Frit 3110: 58%
Calcined Zinc Oxide: 21%
325mesh Silica: 21%

2- Ferro Frit 3110: 50%
Calcined Zinc Oxide: 25%
325mesh Silica: 25%
Add:
Lithium Carbonate: 5%

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Links To Explore:

“Reducing the Firing Temperature of a Glaze From Cone 10 to 6”
by Tony Hansen

I have experimented with reduction atmospheres since school, but it was friend and master crystalline potter Peter Ilsley who started me on his own method during a workshop in Palm Springs, CA.
Since then, I’ve developed my own techniques -but I owe much to this wonderful artist for inspiring me and pointing me in several right directions.

In this case, post-firing reduction defines a second firing used to bring the glaze up to a lower temperature (between 1350-1750°F) than my initial crystalline firings (^11-12). This temperature does not induce a complete melt, but “softens” the glaze. At critical temperatures, the gas/air mixture is adjusted to create an oxygen-reduced atmosphere. The resulting Carbon Monoxide is hungry for oxygen and takes it from the glaze matrix. This thermal/chemical shift alters the metallic coloring oxides in the glaze and changes the color.
A strike firing denotes a similar technique, with the name deriving from a glass-blowing term. The glaze is reheated to a certain point in a neutral or low reduction atmosphere. This can cause subtle changes in the color, sometimes creating iridescent qualities.
For both of these firings, I employ a kiln that I built on site at Wiseman Ceramics Studio. It consists of an old electric kiln, turned on it’s side, to which a burner, chimney, and damper was added.

I have seen potters try similar approaches with old electric kiln shells, but all those were made into updraft kilns. I’ve always found updrafts to be inefficient, uneven, and provide spotty reduction effects. In order to get the atmosphere to move both around and through the work, this kiln was designed to act as a combination cross/downdraft. It works remarkably well!

To be honest, I built this kiln for the fun of it, in wait for the new Geil JH-10 … and, I’ve got to admit that at first it seemed a bit hokey. But the results that come out of it continue to amaze and inspire me onward:

So I’ve been firing in it pretty steady for about 2 years now, and made some modifications to the kiln this past summer.

I learned to fire electric and larger gas kilns manually in school, so although I look forward to exploring glazes with the oxy-probe automated Geil, I have to say that I really value the experience gained by firing a manual reduction kiln in achieving these effects.

Related Links:

Electric Kiln Oil-drip Reduction

Jesse’s Crystalline “Gold” Silver Nitrate Glaze

Using Silver (Ag) as a colorant in a ceramic glaze.

When I began experimenting with crystallines in 1998, the most common frits listed in recipes were Ferro’s 3110/4110 and Pemco’s 283. GF-106 (an equivalent for Pemco 283) was manufactured by the company Glass Coatings & Concepts, until about 2005.
Crystalline artist Kris Friedrich had contracted GC&C to make more of the GF-106, as he was using a base glaze that included it. This base was originally developed by the late Professor Herbert Sanders, and listed in his book “Glazes for Special Effects” (p.30).

Sanders Crystalline Glaze #1:
Pemco 283: 68.42
Silica: 7.45
Zinc: 24.13

Other crystalline artists were aware of GF-106, as well as the Sander’s recipe. Ginny Conrow listed an altered version in John Britt’s “Complete Guide to High Fire Glazes“.
After the separate presentations by Ginny Conrow, Diane Creber, Fara Shimbo, and Kris Friedrich at LatticeStructures™ (2005), many of the attendees were eager to try it. Ironically, due to the poor sales on the GF-106 prior to this, GC&C had no interest in making more.

Several months after LatticeStructures, I was helping Kris Friedrich get ready for hosting the Peter Ilsley Workshop (May 2006). During those preparations, Ilsley and I touched on an favorite frit of his and Derek Clarkson’s, Degussa’s 90208m. This frit, like Pemco 283, had been out of production for years.
Looking at the formula listed in Ilsley’s book, “Macro-Crystalline Glazes”, there was no denying that the 90208m was a perfectly simple Sodium Alumina Silicate, with a great potential for use in crystalline glazes.

Having developed a good relationship with Laguna Clay Company, I discussed the issue with General Manager, Jim Kassebaum, and the Clay Manager, Jon Pacini. Jon had participated in LatticeStructures, and although I had called concerning the Degussa 90208m, it was a pleasant surprise to find that he had already sought out a replacement for the GF-106.
By contacting Nath Viswanath at Fusion Ceramics, it was agreed that a sample of what is currently the substitute for GF-106 and Pemco 283, Fusion’s F413, would be made for Laguna. As Jon was planning to attend the Ilsley event, he said that he would bring the F413, so that side-by-side comparisons could be fired with what remained of the GF-106 and Pemco 283.

Pemco 283 Frit:
Na2O - 16.60%
CaO - 0.30%
MgO - 0.70%
Al2O3 - 5.90%
SiO2 - 76.50%

Fusion F413 Frit:
Na2O - 16.99%
MgO - 0.77%
Al2O3 - 3.34%
SiO2 - 78.90%

This conversation was made even better when Jon referred me to Fusion Ceramics on the matter of the Degussa frit.

At this point, Kris Friedrich was focused on obtaining a good matte crystalline base for the workshop (Ilsley would suggest the Mondre & Manz frit 4067, and the base glaze developed by Peter Fröhlich). But it wasn’t long before Kris realized the potential of the Degussa substitute as well, and contracted Fusion to make a sample of what became the Fusion F644, just in time for the workshop.
Tests came out extraordinary, and the F644 is currently still a favorite flux of mine.

Degussa 90208m Frit:
Na2O - 29.00%
Al2O3 - 9.5%
SiO2 - 62.00%

Fusion F644 Frit:
Na2O - 28.6%
Al2O3 - 9.6%
SiO2 - 61.5%

As a result of the interest developed within the last few years, the excellent frits F644 and F413 are still currently available from Fusion Ceramics.

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Substitutions at a glance:
(Those listed in green are currently available)

Ferro 3110 & 4110 = Fusion F75

Pemco 283 = GF106 = Fusion F413

Degussa 90208m = Fusion F644

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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.

I performed almost 20 tests this past summer (with my glaze assistant Judy Wang) using the elements known as Lanthanides as colorants in crystalline glazes. This was encouraged after meeting David Pier.
I was a private artist at Red Star Studios at the time, while David was teaching at KCAI, and had just had an article on lanthanides published.
The article is still available on line at Bracker’s Good Earth Clays here.
(please contact me if the link does not work).

Update: Jon Singer was invited to LatticeStructures to present on his findings, after having his own article published in Clay Times: “Fluorescent Glazes”.