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

Today I received the latest copy of Spain’s International Revista Ceramica (one of Europe’s top ceramics journals). My work was featured along with the that of several other talented crystalline ceramics artists in an article by Diane Creber.

Krystallos was wonderful. Bill Campbell, his family, and his staff went all out.

The Exhibit was beautiful, the cajun picnic was top notch (thanks Ken!), and the slide show… the whole event was really a pleasure. It was so nice to see everyone again, and Molly and I look forward to the next time we can all get together!

These are the 3 pieces I sent to the Krystallos 2007 Exhibit.

Photography by Jeff Willis.

Initial Crystalline Firing, Oxidation: ^12, Re-fired in Reduction :^015. Multiple Glass-Enamel Firings:^020-019 . 11″ tall.

$900- with pedestal. *Sold*

Initial Crystalline Firing, Oxidation ^10.5, Re-fired in Reduction:^017. Glass Enamel Oxidation firing^020. 7″ tall.

$650- with pedestal. *Sold*

Fired in a 27cu.ft. Geil kiln with Computer Controlled Auto Damper System at Friedrich Pottery. Neutral atmosphere gas firing:^10, followed by reduction at set phases of crystal growth between 2000-1850F. 23k Gold Luster Oxidation Firing: ^017. 6″ tall.

$600- with pedestal. *Sold.*

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.

Oxidation fired:^10.5> Reduction fired: ^017.
The lip of the bottle and pedestal were finished with proprietary glass enamels and metallic luster.
$475-*Sold*