Wiseman Ceramics

This is still a fairly rough draft…
I will probably be adjusting this post as I have the chance, so feel free to check back from time to time.

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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 hitting 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 meant to be excessive, allowing  a window of opportunity to watch the cone bend to the correct angle and stop the hold.
You’ll need 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 heat work 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

<<back to John Tilton’s Workshop Announcement

Workshop Preparation

First I would like to welcome you to this crystal glazing workshop. If you have never made any crystalline pots, you will be behind most of the other people, but you will learn enough to be able to set up your own studio and begin making crystalline pots on your own.

What should you bring to this workshop besides an open mind and willingness to share what you know? Well you should understand that a workshop is not a place to fire loads of pots. Each pot will hopefully be an experiment which you will take home as an example of one of the techniques we will show, and hopefully by studying that pot, you will be inspired. But don’t think that you will end up with thousands of dollars of crystalline pots, and then be disappointed when they don’t materialize. We will be using kilns and materials that are new and so it will be amazing if we are able to really get masterpieces.

It is best that you bring several small pots which are taller than they are wide, and that you have pedestals that fit the bottom of them and a catcher to catch the running glaze. When we did a workshop in Palm Springs a couple of years ago, Diane Creber brought about 25 pots which were somewhere around 3 x 3 x 3 to 4 x 4 x 4. All of them got fired because they fit in around other, larger pots. You don’t have to bring pots that small, but realize that there is only so much kiln space, and large pots are likely to go unfired. Also bowls take up an inordinate amount of space so it would be good to not bring them. We are trying to fire the kilns with the least amount of kiln furniture possible and bowls add kiln furniture.

Small pots are also good because we will be cooling the kiln at a rate that we might not in our own studios. Meaning faster. We only have 2 days so we have to get the pots out early Sunday morning for our post fire reduction on Sunday afternoon.

If you don’t understand the concept of gluing a pedestal to the bottom of the pot and then placing it in a catcher, then it would be useful for you to do some reading before you come. Here are some of the books that I find useful. If you are going to commit to being a crystal potter you will need at least the first three of these books and they are all good.

Macro Crystalline Glazes by Peter Ilsley

Crystalline Glazes by Diane Creber

The Art of Crystalline Glazing by Jon and Leroy Price

The Complete Guide to High Fire Glazes by John Britt

Contemporary Porcelain by Peter Lane

Contemporary Studio Porcelain 2nd Edition by Peter Lane

The Art and Craft of Crystals by Don Holloway (Self Published)

Contemporary Ceramic Formulas by John Conrad

Ceramic Glazes — The Complete Compendium by John Conrad

Glazes for Special Effects by Herbert Sanders (Out of Print)

Nature as Designer by Bertel Bager

We are going to cover several techniques in this workshop which are beyond the beginner’s phase. Again, if you are a beginner that is OK. We will cover the basics too.

We will be doing some post fire reduction so if you have some small crystalline pots which have copper or manganese based glazes, you may bring them for post fire reduction. Hopefully we will do a firing on Saturday night which will give us pots for post fire reduction on Sunday, so you don’t absolutely need pots when you come. But if you have some of those pots we can do a post fire on Saturday too. Pots glazed with small percentages of copper and manganese glazes change dramatically in post fire reduction — some of the coppers can go bright red from green.

We are also going to try to use some encapsulated stains in a slip which we will put under a crystalline glaze to obtain colors that are impossible to get any other way. One of the masters of this style is Denis Caraty. See for some examples of his work. Denis feels like putting the slip on a greenware pot and then glazing without bisquing is the best way to do these so if you have some dry greenware pots and pedestals, please bring them. I am working with Denis’ method at headquarters here in Alachua, but there are other ways to do these. The final products have beautiful crystals on bright red, orange, and yellow backgrounds and they are impressive, to say the least. Jan Anthony has done some very successful works with this technique and she will be sharing her methods too. I’ve also talked to Jamie Koslowski about his ideas too and he makes some of the best.

I hope to be able to fire some matte crystalline glazes too. At the very least I will bring some matte crystalline glaze that we can use. I’d like to be able to do these with American frits so that you could work with them after the workshop, but I do not have that yet. We also have a glaze called Roy’s Spotted Matte which is matte in oxidation and quite different from the matte crystallines that I am currently working on.

I am very much looking forward to this and to being with you again.

John

It’s so cold, that I thought I got the coolest crystalline glaze ever… until it thawed.
It’s so cold that i don’t want to joke about how cold it is. Seriously, it’s not funny - it’s really too damn cold.
-How cold?:
I have to warm up my thermocouples with a lighter and set the first ramp to hold at 75°F for 5 hours (instead of setting a delay). Otherwise I get an “Error Code-6“, because the controller can’t read something SO COLD!!!

I’ve tried hanging a “warming bulb” inside the kiln, and also used a small space heater when I was in more of a hurry. But you can’t program a delayed early morning start (when it’s going to be the coldest yet) with any one of those in there –it might smell bad. So I heat the TC’s with a lighter and then program the first ramp with a hold at 60-90°F for “X” number of hours.
The nice thing is that whether I do a delay or a preheat ramp/hold, the new kiln doesn’t lag like other kilns I’ve fired. So my rate of rise is always within a few degrees/hour of what I set (even the -20F night we had here last week didn’t slow it down), and I can pretty much calculate when it will hit peak … I’ve never been off by more than 5 minutes.

This year I’m going to build an actual kiln room (rather than just a walled off area) with a low ceiling and door. I’ve been waiting on the Geil to arrive before I do this…
Once a room is up, I’ll be able to use the space heater the way it’s supposed to be used… I’d only need to keep the room above zero, and I could even warm up the room more prior to when I would be in there loading. Oh, oh… the JOY!!!
Did I mention Wisco gets a little chilly?

These are secondary crystals shapes which formed in my glazes during the winter of 2007-08. I’d never noticed these in my glazes prior to this time period, and thought that some were faults due to colorant impurities, insufficient sieving of the glaze, etc.

The crystal in reference here is the darker blue one:

These are some of the first ones I noticed, with mostly perfect triangular shapes –these particular crystals did not show until after the glaze was reduced:

This one is like a kaleidescope. It also reminds me of the water crystals photographed by Dr. Masaru Emoto:

These two formed rectangular shapes:

I’ll be updating with more info and images as they come…