Wiseman Ceramics

Has anyone seen the commercial concerning a popular allergy medication where a sculptor (wearing eye protection -but no dust mask) is creating from a block of stone with what appears to be an angle grinder? Airborne particles visually fill his immediate area as he works –then the scene cuts, and he says he uses _______ for all his allergy issues…
The next time I saw it, I noticed a cat sitting in the room with him. Were they honestly trying to insinuate that the cat dander is the real concern for this guy’s nasal, bronchial, and lung tissue irritation?

Silicosis is the result of silica (from clay, stone, glass, etc.) dust, which is toxic to the lining of the lungs. When silica particles contact lung tissue, a strong inflammatory reaction occurs. Over time, this inflammation causes the lungs to become irreversibly damaged. This falls under the term fibrosis, a condition which is both debilitating and deadly.

From the searching I’ve done, the “sculptor” is portrayed by actor Jon Eric Preston. On the medicine’s official website, all the actors are “representative of the real symptoms that allergy sufferers experience and the clear relief that ________ delivers in many real life situations”.

Ok -well, in real life Preston is skilled at many things from snake handling to firearms. Perhaps next they’ll ask him to do an adhesive bandage commercial where he acts out the fine art of Russian Roulette…

Related links:

U.S. Department of Labor: Facts on Silicosis

Silicosis and Screening by Edouard Bastarache

This is still a fairly rough draft…
I have posted it sooner than planned because a friend (who was recently accepted into Alfred University –go Mark!) has asked me to cover some basics. I will probably be adjusting this post as I have the chance, so feel free to check back from time to time.

_______________________________________________

I’d like to start out with a suggestion on what not to do.
When I started with crystalline glazes almost 10 years ago, I made the mistake of seeking out as many recipes as I could, then testing all of them over and over. I spent several weeks mixing and creating tests just to load a kiln, and came to terms with the fact that “shotgunning” 30+ different bases doesn’t get you anywhere as fast as you think.
The main reason is that because there were so many glazes, I couldn’t focus on the consistency of each test. I may very well have had some wonderful glazes at any one point, and never known it because of the “sloppy science” that takes over when you overwhelm yourself with too much work and information.
So, the first thing I offer is to find a proven base and stay with it. Don’t move on until you figure a firing schedule that works, then make adjustments from there.

Keep in mind that erroneous results can be achieved within any step of the process, so stay sharp!

TO BEGIN

First, it is probably a good idea to understand how to read a glaze recipe.

Second, obtain enough of the basic ingredients (frit, zinc, silica, titanium) to cover several rounds of testing, and continue glazing other pieces beyond that. Make sure that you are using the same ingredients from the same air-tight container every time.

Third, hydrate your glaze using the correct amount of water.

Fourth, establish/check the specific gravity each time you mix a new batch. You also need to be sure that you have the same water content in your glaze every time you apply it to a test, whether you mix another batch or use the remaining glaze from a successful test.

Last, always verify that the peak temperature you think your controller is hitting is accurate –Go Here for more on this. You don’t need to adjust the controller (e.g., if your using a community/school kiln) if it’s not off by much, as long as you verify the peak at each firing. To do this, place a self-supporting cone in view of the spy hole and be there when your kiln approaches your predetermined top temperature.
Actually, I strongly suggest not ever relying completely on your controller … for testing or otherwise. When it’s time to move on, get another kiln, or simply replace the controller/thermocouples, all your notes will still make sense, because you fired to a cone rather than a digital display.

Below is a glaze that does well between ^8-10. The exact cone value depends on the crystal/background ratio you want, how thick you apply the glaze, whether you have a vertical, flat, or wide shouldered form, etc.

Ferro Frit 3110 or Fusion Frit 75: 51%
Calcined Zinc Oxide: 25%
325mesh Silicon Dioxide: 24%
Add:
Titanium Dioxide: 6%
CMC: 1-2%

Another recipe without titanium
(listed on P.141 in John Britt’s book Complete Guide to High-Fire Glazes):

Ferro Frit 3110 or Fusion Frit 75: 51%
Calcined Zinc Oxide: 23%
325mesh Silicon Dioxide: 22%
Kaolin (Grolleg): 2.5
Alumina Hydrate: 1.5

When I fire tests, I use a thrown form such as this:

The form is 6 inches wide at the base, offering enough surface area to give you adequate information after firing, and provides the necessary reservoir for catching glaze run-off.

1- Apply glaze consistently on each test. By this I mean paying attention to the thickness as well as where you apply thicker layers on the test. The general rule I follow is 2mm on top 1/3 of test, 1-1.5mm on the rest of the form. I prefer spraying, and since you’re only using one or two glazes, it’s pretty painless.
2- Mark a pin or needle tool, using a file (paint/ink rubs off) in 1mm increments from its tip. Use it to test how thick the glaze is applied to each piece before firing.
3- Fire to peak, using a self-supporting witness cone (^9-10).
4- Keep detailed notes concerning all of these steps. BTW: If you don’t keep notes, don’t bother reading further, and feel free to forget everything you’ve already read -because, well… that’s what will eventually happen anyway…

FIRING

Here is a recommended schedule:
Preheat @100F. Hold 30min - 1 hour (0.30-1.00).
Ramp 325F/hr to 2200F. Hold: 0.00
Ramp 108F/hr to 2348F. Hold until ^10 is reached.
If you use a self supporting cone, the tip should be level with the top of the triangular base.
If firing manually, shut the power off at this point and let the kiln cool as fast as possible to the first hold. If using a controller, most have the option to stop a hold using the “Skip Step” function. On my controller (Dynatrol/Bartlett V6-CF 700) this is done by inputing the keys: Review Segment-Enter-Enter. So to get my peak, I can program a hold at a slightly lower temperature for about 20 minutes. This time is excessive, which allows you a window of time to watch the cone bend to the correct angle and stop the hold.
You’ll have to learn the limits of your kiln. Here is the specially designed kiln that I fire with. Some kilns don’t cool as fast as others, so there may be enough residual heatwork to bend the cone past perfect. You’ll need to experiment with where you need the cone to be when you stop that stage of the firing, so that it achieves the perfect bend while the kiln is cooling.

After hitting your peak temperature, use this holding pattern to grow crystals:
Hold 1: 1985F for 2 hrs.
Hold 2: 1925 for 2 hrs.
Hold 3: 1985 for 2 hrs.
After the 3rd hold, shut the kiln off (or allow the controller to do it) and let the kiln cool naturally.

After examining the tests you can decide where to proceed. If you have too many crystals, slow the final ramp to peak. If too little, increase that rate of climb. Try this before you alter the glaze base. Understand that increasing/decreasing that rate will change the temperature you need to achieve to bend the same cone.

CREATING REFERENCES

Once you’ve established the right firing cycle, I recommend that you continue in this way:

Take the base glaze and calculate each of the three main ingredients (frit, zinc, and silica) up and down by 3-4%. Mix and fire these tests in the same specific manner you did for the original glaze. These will probably not be all that nice, but keep these tests as reference, as they will be invaluable when trying to solve problems or proceed in the future.

Lastly, try adding colorants.
Cobalt at 1-3%, Iron at 1-5%, Copper at 1-6%, Nickel at 1-3%, etc.
Don’t let this small example list or the percentage limits above keep you from exploring further. I’ll write more on this in another post later.

FINALLY…

I have volumes of journal entries and firing notes leading me to the point I’m at now, and I am constantly reminded of how I’ve only scratched the surface.
As such, there is little way I can show you the limits of glaze testing beyond what is listed above, and I really have no desire to steal your own potential. A unique experience is the best way to succeed and have your work stand out.
The last thing I’ll leave you with is, have fun! If you learn to enjoy the process, your failures will have less of an impact, and your successes will become stepping stones on an amazing journey.

A glaze recipe is almost always listed as a “percentage or batch formula”, adding up to 100.  Every once in a while you’ll run across something that is slightly off (I was shown one adding up to 98.63% recently) -but that’s uncommon.

As stated in my post “Getting Started with Crystalline Glazes“, when people ask me for a crystalline glaze recipe (^9-10), I offer them this to start with:

Frit 3110: 50%
Zinc Oxide: 25%
Silica: 25%

50+25+25=100%

The above would technically be referred to as a percentage formula. If you wanted to make a small test, you’d probably just want to mix up 100 grams.
This would then be called a 100 gram batch formula:

Frit 3110: 50 grams +
Zinc Oxide: 25 grams +
Silica: 25 grams
= 100 grams

Ok, so say you find that the glaze works, and you want to mix up 600 grams to test further…

Look at the above formula again, like this:

Frit 3110: 50 (x 1) = 50
Zinc Oxide: 25 (x 1) = 25
Silica: 25 (x 1) = 25
=100, right?

So for 600 grams:

Frit 3110: 50 (x 6) = 300 +
Zinc Oxide: 25 (x 6) = 150 +
Silica: 25 (x 6) = 150
= 600 grams

For 800 grams, multiply each part by 8,
for 950 grams, multiply each part by 9.5,
and for 1000 grams, multiply by 10.

In John Britt’s book “Complete Guide to High Fire Glazes”, I list an Alkaline Base Recipe:

Frit 3110: 51
Calcined Zinc Oxide: 23
Silica: 22
Grolleg Kaolin: 2.5
Alumina Hydrate: 1.5
= 100%

The above formula is called a base glaze. Base glazes typically come out clear or white. To this you can add colorants, modifiers, binders, etc. These are not usually listed as part of the formula, but you’d still multiply each one by the same number, to get an equal proportion in the glaze.
For 750 grams…
Frit 3110: 51 (x 7.5) = 382.5 grams
Calcined Zinc Oxide: 23 (x 7.5) = 172.5 grams
Silica: 22 (x 7.5) = 165 grams
Grolleg Kaolin: 2.5 (x 7.5) = 18.75 grams
Alumina Hydrate: 1.5 (x 7.5) = 11.25 grams

To get the dark blue glaze pictured on pg. 137 of Britt’s book, add:
Cobalt Oxide: 3 (x 7.5) = 22.5 grams
Manganese Dioxide: 3 (x 7.5) = 22.5 grams
Red Iron Oxide: 3 (x 7.5) = 22.5 grams
Bentonite (or CMC as a binder): 1 (x 7.5) = 7.5 grams

So you have 750 grams of the base + 75 grams of colorant and binder = 825 grams.
Now you can use that result to calculate how much water to add.

Relevant Links:

Adding Water & Suspenders/Binders to a Glaze

Specific Gravity

Glaze Application: Spraying & Spray Guns

Hydrating the Glaze:

To hydrate a glaze for application whether it be by brushing, spraying, dipping, etc., you need to achieve the same result each time you go to glaze. Every glaze is going to act different and require varying levels of water content to get the consistency that works for you.

When I discussed the reading of a glaze recipe in another post, I left off with this example:

Frit 3110: 51 (x 7.5) = 382.5 grams
Calcined Zinc Oxide: 23 (x 7.5) = 172.5 grams
Silica: 22 (x 7.5) = 165 grams
Grolleg Kaolin: 2.5 (x 7.5) = 18.75 grams
Alumina Hydrate: 1.5 (x 7.5) = 11.25 grams

To get the dark blue glaze pictured on pg. 137 of John Britt’s book, add:
Cobalt Oxide: 3 (x 7.5) = 22.5 grams
Manganese Dioxide: 3 (x 7.5) = 22.5 grams
Red Iron Oxide: 3 (x 7.5) = 22.5 grams
Bentonite (or CMC as a binder): 1 (x 7.5) = 7.5 grams

This glaze has 750 grams of the base + 75 grams of colorant and binder = 825 grams.

When calculating how much water to add, weigh each component, and multiply by the percentage of water content you need. Again, every glaze is different –clay content, modifiers, and even certain colorants factor into this. So you’ll have to add water, adjust as needed, and record that % for later reference.

Let’s say that you want to start with 50% water, take the 825 gram example and multiply by 50%:
825 x 0.50 = 412.5

412.5 can translate to cubic centimeters (cc), milliliters, or grams, depending on how you wish to measure it out. I use a graduated cylinder (ml) or large syringe (cc).
50% water will probably not be enough, but it’s better to err on that side, as you can always add more water.

A crystalline glaze contains little to no clay and usually a large amount of fritted or calcined components. If you add only water to it, it will soon settle like fine sand, and be extremely difficult to work with. When applied to your work, it will crack, peel, and flake off during drying. This is why suspenders and binders are added.

Gum Water Solutions:

In the case of the above recipe, 1% Bentonite or CMC is listed (1% is offered as a rough figure only). Either must be thoroughly mixed with the other dry ingredients before water is added, or it will form irregular clumps. I prefer to mix them into water before hand. You can buy pre-mixed “gels” from commercial suppliers, but it’s hard to know how much of what you will be adding, so I like to make my own. Take note that if your glaze recipe has a large enough clay content, then additives like these are likely unnecessary, and can result in a gummy mess.
I had heard about pre-mixing CMC, etc into water through potters such as Jeff Zamek. But it didn’t sink in just how simple and effective it could be until John Tilton and I visited our friend Kris Friedrich at his studio. I have since kept premixed & hydrated forms of many ingredients in air tight containers, ready for use.

Using CMC as an example then, I often add 0.5-2.0 grams of dry CMC powder per every 8oz of water. The amount of CMC necessary will depend upon what type of CMC you have. Some CMC will actually contain larger particle wood pulp as a filler, whereas certain “food grade” varieties are so powerful that the 0.5gCMC : 8ozH2O ratio is enough.

Blend the powder into warm water until mixed, let it sit for an hour or so (or preferably overnight), and blend again before use. This pre-hydrated gum solution can then be mixed with the dry glaze batch to produce a usable consistency (52-72% of the dry glaze weight works well in my crystalline bases).

Include the weight of all additions (colorants, etc.) and round the decimal.
Example:
825 grams of dry ingredients X 0.55 = 453.75 (round to 454) cc/ml of gum solution.

I mix the dry glaze ingredients and gum solution in a blender until it’s uniform, and then pass the glaze through a 80-100 mesh sieve. One trick is to add the water to the glaze and let it sit for a 1/2 hour or so. It will mix faster and go much easier on your blender.

Some CMC’s are infused with a fungicide.  This prevents it from decomposing and losing it’s strength.  Many crystalline artists agree that keeping their glazes for long periods of time has bad consequences; however, if you choose to do so, simply add 0.02% Copper Carbonate to the gum solution when mixing it up.  This will deter organic growth and at that level, it won’t discolor even white/clear glazes.

Lastly, I suggest weighing the hydrated glaze to obtain a specific gravity. By doing this, you can adjust the glaze if, e.g., it loses water during storage. If the specific gravity is off, your viscosity will more than likely change as well, and you can easily add too much or too little glaze during later applications, skewing the results.

Relevant Links:

Glaze Suspension & Binder Products I use.

Reading, Calculating, & Measuring a Glaze Recipe

Specific Gravity

Glaze Application: Spraying & Spray Guns

The specific gravity of a liquid is simply the weight of the dry components in relation to the water. If the specific gravity of your glaze or slip changes too much, you could be applying too much or too little, which may prevent you from getting repeatable results. Finding the correct specific gravity for your methods is part of a trial and error process. As a starting point, the target for most glazes and slips is between 1.50 -1.80. Once you have found what works best, taking and recording a measurement will allow you to adjust the glaze as it loses water during use, storage, etc.
I usually try to keep my glazes within a “certain window”, and use the specific gravity as a guide for returning to, when things get far enough off. Having said that, some of my glazes are extremely application sensitive (Reddn’d Rainbow is a good example), so I’ll take particular care to be accurate with those.

Since the weight of 100ml of distilled water equals 100 grams, the best way to get a reading is by taking a 100ml sample of your glaze or slip and weigh it using an accurate scale and a graduated cylinder.
Tare the scale to the weight of the graduated cylinder, and carefully fill it to the 100ml mark.

Example:
(100ml water = 100grams)
100ml slip/glaze = 160grams.
The specific gravity is said to be 1.6, as it is 1.6 times the weight of water.

If the Specific Gravity is too high, you can lower it by adding water.
Take care to add only water (not gum solution). The binder or suspension agent does not evaporate with the water, so the water content alone is all that needs adjusting. Also, understand that it takes much less water than you think to thin a glaze, so adjust a little at a time.
If the specific gravity is too low, add more dry materials in the correct proportions regarding the clay or glaze formula.

Temperature also plays a role. In the winter, I have my studio thermostat programmed for a lower temperature during the late night/ early morning hours when I’m not working. I have therefore noticed a difference when measuring the specific gravity first thing in the morning, as compared to later after the heater’s been running for several hours. I get past this by blending the glaze for a few minutes each time I take a reading. Be careful not to blend too long, as the high shear friction can cause the liquid to heat up and skew the reading.
To be really precise then, the readings should actually be done with a thermometer as well.

In a future post, I will discuss how Viscosity/Rheology factors into all of this.

Relevant Links:

Getting Started with Crystalline Glazes

Reading, Calculating, & Measuring a Glaze Recipe

Adding Water & Suspenders/Binders to a Glaze

Glaze Application: Spraying & Spray Guns

Whether you’re trying to achieve an accurate firing via a peak temperature hold or a calculated ramp, it’s a good idea to calibrate your thermocouples (TC’s) before relying on the factory setting in your controller.

Hopefully you have Type S TC’s … if so, you’re not going to need to calibrate them again for some time. It’s pretty ridiculous that Type K’s are used past 2100°F these days. If you have them and plan to go beyond that temperature, you’ll need to check and adjust for “drift” about every 5-10 firings.
No matter which TC’s are being used however, I always suggest using witness cones to judge accuracy on each firing.

___________________________________

There are two ways to calibrate your thermocouples. One way is to fire your kiln, inspect the cones afterwards, and then make a guess as to how to offset your TC’s. This can take anywhere from a few to several firings.   I hear of many who do it this way, and honestly- I’ve never understood why.

A more effective approach is to record what your kiln controller reads during a firing, when you see the cone achieving that perfect bend, then establish the offset from there.

Here’s how:

1- Check with your manufacturer to see what the factory TC offset for your kiln/controller should be set at, then verify that each TC is offset to the number they give you.

Example: L&L Kiln’s factory offset is usually 18 (not zero),
when using the Bartlett V6-CF control board & Type S TC’s.

2- Stack your kiln with stilts and shelves so that an Orton self-supporting witness cone can be viewed through each spy, and place another in the center of each shelf. I also put in glaze tests in addition to cones to get as much information as possible. I prefer not to fire a “light” kiln, as the loss in thermal mass could prevent an accurate result, so I use softbrick and/or extra stilts to take up the empty space.

3- Program the controller for a rise of 108°F/hr during the last 150F prior to peak.

Example: ^10 = 2345°F at 108°F/hr.
So program a rise of 108°F/hr from 2145°F to 2345°F.

4- Set a delay if needed so that you can be there around the time the kiln reaches peak. …Obviously, you’ll want to err on being early.

5- Record the temperature of each TC at the time the corresponding cone bends perfectly. Understand that the readings may be different for each zone/TC, and that they can be offset independently.
The perfect arch (90° bend) for a self-supporting Orton cone is when the tip is level with the top of the triangular base.

6- From here you can figure out if your kiln is under or over firing, and by how much.

7- Your controller can be programmed to offset the TC readings by as much as 50° in either direction. To adjust the TC offset on a Bartlett V6-CF, you will need to calculate the number to offset (also refer to Bartlett’s online manual):

To lower the temperature/heat work in the kiln, start with the factory set point and add the number of degrees to compensate for each thermocouple. This will raise the temperature displayed.

To raise the temperature/heat work in the kiln, start with the factory set point and subtract the number of degrees to compensate for each thermocouple. This will lower the temperature displayed.
To program a number below zero: type in “90″, immediately followed by the number of degrees to compensate… think of the 90 as a (-).
Consider that since 18 is the factory set point for an L&L with Type S TC’s, you should not need to go below zero. If you find that you do, I would suggest contacting the manufacturer of your kiln or controller.

___________________________________________________

After going through this process with my new kiln, I found that my top TC needed an offset of 19 and my bottom at 25. Leaving it at the factory setting of 18 would have resulted not only in over firing, but also in uneven heatwork between the zones (sections) of the kiln. Go here for more on this.

Artists today must be multi-talented, to say the least. As a ceramic arts student, I thought that while I was in school, all I needed to focus on was clay/glaze chemistry and making ceramic forms. But unless you have an unlimited budget to “hire out” to professionals, you have to be part artist, potter, chemist, photographer/graphic designer, accountant, promoter, writer/editor, electrician, gas technician… the list could go on and on.

I can’t stress the importance of archiving your work through imagery. I document most of my tests and kiln firings in the same way and include those images in my notes.
Having said that, of all the learned skills listed above, photography is one of the most frustrating tasks I’ve taken on.
What works for one person, won’t work for another… heck, what works for one pot won’t work for another! But here’s some information that may help.

The Camera:

Choose a camera that suits your needs. There’s no use spending $900-$3000 on a camera, if you’re not going to use half the settings available.
I went with a digital format. I can remember just 7 or 8 years ago, I was still having to deal with slides when sending info to galleries, publications, etc. Now most accept, and even prefer, high quality digital imagery supplied on a disk. It’s easy to store and it usually doesn’t need to be returned.
My camera is considered a standard “point and shoot” model. The features I was drawn to were:
8.3 megapixel CCD,
4X digital zoom/10X optical zoom,
2-1/2″ LCD screen (the bigger the better)
Manual exposure controls: ISO adjust for shutter speed / aperture combinations.

Do your homework before you buy… my camera actually has some bad marks in terms of it’s score, but when I looked past the overall “star ratings”, I realized that these minuses were in considering the video mode. I mention this to show how you can get a really good camera for what you’re trying to do, if you focus on what you’re trying to do. If I want to make movies, I’ll get a video camera…

Accessories:

The best accessories I can suggest would include a good sized memory card (1GB or larger), a good telescoping tripod, a protective camera case, and an extended “no-hassle” warranty on the camera itself. My warranty was around $50 for two years, and covers all but “complete submersion in water”. Photo editing software is valuable for minor tweaking, but most publications won’t accept images that are heavily edited, so you’ll always want to focus on taking good pictures in the first place.

Lights:

Get some light stands that will allow you to try different types of bulbs. You’ll want to experiment with tungsten, fluorescent, incandescent, halogen, Metal Halide, etc. Keep in mind that some bulb types also have different color (Kelvin) ratings. I can’t really say what each person will prefer, but I’ve had good success with the new compact higher wattage fluorescents.

3-Diffusers, Light Tents, Reflectors, and …Snoots! :

If you’re going to go with a light tent get the largest one you can buy/fit in your space. Most of them are collapsible, but you’ll need a sturdy surface that is wide enough to put it on, and also high enough to use a tripod for your camera.
Mine is 59″x59″x59″. I bought it after seeing Bill Campbell’s then photographer, Jeff Willis, using a similar one at Campbell Pottery. Kris Friedrich also uses a larger tent.
I had tried a smaller 28″ diffuser box that is probably great for shooting jewelry, handbags, etc. It still does a great job of capturing Molly’s (hear it: non-reflective) hand spun fibers, but it was agonizing when shooting my pots.
The walls of the smaller tent diffused the light into large “window panes” reflected onto the piece I was trying to capture. The larger box doesn’t do this, but you have to learn how to use your camera in a diffused situation or the image will look too soft/out of focus, especially along the edges of the piece.

Reflectors and soft boxes always gave me similar problems to the smaller light box.

The best pictures I ever had were taken by a pro-photographer in Kansas City. He allowed me to be there as he was shooting, and had his camera hooked up to a laptop that showed what the camera’s view screen did at a much more discernible size. In this way, we could identify potential glare, position, color issues prior to taking the actual picture, loading the image onto the computer… etc.
We tried several different ways, “going by the book” in terms of lighting, aperture settings, diffusers, reflectors…
We finally decided to put a pot on the large infinity board platform that he uses to shoot family portraits. Then we took some lights and positioned them as far away as possible, so that they light the pot well, but the reflections of the light themselves appeared as small glints on the piece. Viola!
The glints from the lights could very easily be edited without compromising the image. But they actually gave the piece a nice 3-dimensional look, so I left them.

I lost access to that photographer when I moved, but now I try a similar approach, using the large light tent, colored backdrops, and spotlights from as far back as the light output will allow.
In an attempt to increase the light level and recreate the “small glint” effect above, I have used a simple technique by making a “snoot“. A snoot is a tunnel for the light to go through that restricts it, except for the exact direction in which the light is pointed. With cooler running fluorescents, you can make this from paper or cardboard forming a cone or tube shape. One can also be made from ridged aluminum dryer ducting (a length of 8-12″ works well).

Again, I can’t say that I’m completely happy with my pictures currently, but I think the learning process is coming along.
Hopefully this explains some of the good and not-so-good images on my site, and helps others find a way to build an image library of their own work.

I ESPECIALLY welcome comments/input concerning this post!

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.

With almost 800+sq. ft. to work with, I strive to keep my studio as dust-free as is possible:
*I use an exhaust booth for spray glazing and rotary tooling, and a separate vent setup for the glaze mixing table (both exhaust to outside).

*I wipe everything down with a damp sponge, wet mop, etc.
*I use a vacuum that is mounted outside of the studio, eliminating the risk of air/dust leaks, with a hose coming in through a sealed port. It has a standard filter to catch the big stuff, while the finer dust exhausts safely outside.
*During the warmer months I use two sets of intake & exhaust fans set at opposing ends of the studio, creating a continuous draw of fresh air through the workspace.

Regardless of this, I still find dust settling on the tables, floor, and equipment… I’m referring to the really dangerous fine particle stuff which stays airborne for hours after it’s set afloat. Because I can’t run the fans in the winter, & therefore the dust accumulation increases during this part of the year, I’ve installed two 360° HEPA air filtration units at opposite ends of the studio.
I run the HEPA’s on “low” during the day and turn them to “high” at night when we aren’t working, as at that speed they do just as good a job at churning the dust up as they can at capturing it.