Adding Water, Suspenders, & Binders to a Glaze

admin | Glaze Research, How-to & Studio Info | Monday, January 28th, 2008

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

4 Comments »

  1. Note: This comment and the following response were made prior to a re-writing of the above text. Several grades of CMC are available, so you will have to test yours to find the right ratio to mix.

    Hey Jesse… My recipe from Kris’ has this same amount as you quote to form the CMC solution, that is then diluted 1 cup CMC solution to 6 cups water… I don’t see you mentioning the dilution. Are you saying you use it that thick straight into your glaze?
    i.e. ….. you say above “CMC as an example then, I often add 25-30 grams of dry CMC powder to 5 cups of water. The amount of CMC needed will depend upon your glaze. Blend the powder with warm/hot water until mixed, let it sit for an hour or so, and blend again before use. This pre-hydrated gum solution is mixed with the dry glaze batch to produce a usable consistency (52-72% of the dry glaze weight works well in my crystalline bases).

    I am finally working on getting my specific gravity right for every single glaze… I usually just start with about 60% cmc/water solution and take it by feel, but I’ve been getting it a bit thin (mistake) lately, so I’m finally deciding to get more particular about the measure…

    Comment by Holly McKeen — March 7, 2008 @ 5:24 pm

  2. I don’t recall diluting the CMC solution again when I was at Kris’ for the Ilsley Workshop
    But either way, it looks like you’re using about half (or is it 1/6?) as much CMC as I do.

    To get more accurate, we’ll need to rid ourselves of that silly American standard of measurement:
    5 cups = 1200ml (oooo, a nice round number… ain’t that nice? Man, that almost NEVER happens).

    25g CMC into 1200ml H2O means that there is 5g of CMC per 240 ml of H20.
    If 60ml of that solution is added to 100g of dry ingredients, then 1.25g of CMC is now part of that glaze.

    In terms of diluting it again –let’s start over:

    6 cups = 1440ml H2O
    5 cups = 1200ml H2O
    25g CMC into 2640ml H2O means that you have 5g in 528ml –or almost 0.0095g CMC per ml H2O.
    If 60ml of your final mix is added to 100g of dry ingredients, that means 0.57g of CMC is in that glaze… again, that’s about half as much as I use.

    Now, if you meant that you dilute it by 1/6:
    1/6 of 1.25 = 0.2g CMC
    Wow, that’s not a lot… (Added note on April 24, 2008: See the comment below this one).

    In James Chappell’s “The Potter’s Complete Book of Clay and Glazes”, most of the glaze recipes follow with “add 1 tsp. CMC”.
    Yeah… off the top of my head, I couldn’t tell you what 1tsp. of CMC weighs in at, but Jeff Zamek steps up in “What Every Potter Should Know”, by referencing between 0.125%-2.0% dry CMC powder by weight in a glaze. Keep in mind, however, that most of the glazes listed in Jeff’s book had a clay content of 4% or higher -or asked for bentonite.

    Kris Friedrich also lists bentonite in his recipes, while John Tilton often adds EPK, so both would understandably use less CMC than I.
    For the example recipe in this post, I said to use Bentonite OR CMC.
    So, what’s the clay/bentonite situation at Greendale?

    Speaking of which, make sure y’all check out Holly McKeen’s site.

    Comment by Jesse Hull — March 7, 2008 @ 8:40 pm

  3. Hey again Holly-

    I recently ordered some CMC from a supplier that had taken advantage of a good deal.
    A colleague of his owns a large food service supply facility, and contacted this ceramic supplier saying that some “food-grade” CMC had been returned to him. For various reasons, he couldn’t sell it again within his usual market, so they made a deal on about 1800lbs of the stuff.

    I had created quite a thick/viscous gel from this recent CMC powder, using the same measurements that would have yielded a much thinner liquid with the CMC product that I’m used to.
    I was told that this “food-grade” CMC was many times more pure than other types. I also learned that lesser grades will actually add finely sieved, but otherwise unaltered, wood pulp –and therefore have less of the gum forming properties.
    I had to dilute that gel 7 more times with straight water to get it to a usable state. I could have probably diluted it a little less, or even a little more, depending on my method of glaze application, but I’ll run with this concentration for a bit.

    As long as it works for me, I’ll certainly be ordering more of it –getting anywhere from 5-10 times as much product for the same “market price” of CMC (@$8-10/lb.) would be great.

    As there are probably many grades of CMC available, I have rewritten the information in the page above to reflect this, offering the: “0.5-2.0grams CMC : 8ounces H2O” suggested dilution rate.

    ~jesse.

    Comment by admin — April 24, 2008 @ 9:52 am

  4. Hi Jesse….I am trying to have the Gold Silver Nitrate recipe done by my local supply company….They have no idea what MAGMA Binder is…can you elaborate????? Cathy

    Cathy, switch out the silver nitrate per the advice this link: http://jessehull.com/2008/05/25/using-silver-ag-as-a-colorant-in-a-ceramic-glaze/
    Then use CMC rather than MAGMA.

    Comment by Cathy Linfield — August 6, 2011 @ 4:58 pm

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