Guidelines for Making Glazes



Glaze-Making Committee Guidelines

Important safety tip: Wear a mask when making glazes! Breathing the dry glaze chemicals is hazardous! Suggest that anyone else in the area is also wearing a mask.

Making Established Glazes:

• Check the list and/or buckets to see what glaze needs to be made. Try to mix the oldest requested glaze on the list.

• Find recipe in the glaze box and then see if the ingredients are available. It is helpful to jot down the ingredients & amounts on scrap paper so that you can check them off as they are added. The Cone 10 buckets hold 7000 – 8000 grams in total*. When a bucket has about 1½” left in the bottom, mix up no more than 6000 grams. In order to keep the larger buckets from becoming too heavy, it is recommended that you make between 3500 and 4500 grams of a glaze. The online Glaze Cabinet located under the Member Tools tab of the member website can be used to access the recipes and provide the math calculation for the needed quantity.

• Find a clean bucket.** Use small buckets for l000g, and use large buckets for all others. Mix in and add warm water in the same # of milliliters of water (or slightly less) as grams as the dry chemicals indicated on the recipe card. Keep some of this water aside to use for rinsing later. (Exception: if the recipe has Bentonite in it, mix all the dry ingredients together with the Bentonite first, then pour all into pail with water). (FYI: 1000 grams = 1 milliliter = approx. 4.5 cups of water)

• Set up the scale with the stainless steel bowl. Make sure the scale is set for weighing grams. Use one of the smaller metal bowls that are usually kept on the windowsill next to the sprayer and a DRY scoop. Plug in the scale, put the bowl on the scale and press the “Z” button to zero out the scale. This way, the scale doesn’t include the weight of the bowl when weighing the ingredients. Measure each ingredient separately taking care to get the weight as exact as possible, and adding them to the water. Keep the bowl dry. Ensure that the scale is still zeroed out for each ingredient as you add.

• When all ingredients are included, mix carefully, then sieve into a fresh bucket. Include and sieve any leftover glaze from the bucket of glaze you are mixing. Clean the now empty glaze bucket, including the lid! Then sieve AGAIN, into the clean glaze bucket. Sieve the new glaze through a screen at least three times. Note: It is easy to add too much water. After two screenings the glaze should have the consistency of light cream. Use your reserved water to rinse out the sieve into the glaze bucket. Add 1 – 2 Tbsp. of Epsom salt dissolved in warm water to the glaze bucket. This helps keep the glaze suspended. Most glazes have a specific gravity of about 1.45 if using the hydrometer. (Clear glazes should have a specific gravity of about 1.35)

• Next, dip one brown clay and one white clay test tile. Leave three-quarters of an inch clean with the first dip, let dry, and then dip half that again. Label the tile with the correct glaze name using an underglaze pencil or iron oxide wash and put them on the shelf to be fired.

• Label the lid and bucket with masking tape with your name, # of grams made, & date. In addition, put this information on the on-line Glaze-making clipboard along with the name of the glaze. (This tracks your hours!)

Follow Up:

Check the outcome of the test tile firing. If the glaze looks as it should, discard the old test tile and replace it with the new one. If the test tile does not look right, check your recipe sheet with the original in the box. Check with the Firing Committee for any misfires and consult with other members of the committee.

Thanks for making glaze!

*Cone 6 buckets hold about 5000 grams. Raku containers hold approx. 1500 grams for the larger containers. When mixing raku glazes, use about ¼ of dry ingredients for amount of water to add—it should be the consistency of sour cream.

**Some glazes need to be mixed in the ball mill to make the colorants integrate completely into the glaze. Celadon and other high iron glazes are especially adaptable to the use of the ball mill for complete grinding of the chemicals. (See separate instructions on how to use ball mill)

Developing & Testing New Glazes

Before taking on the task of testing or developing a new glaze, first confirm that all established glazes have sufficient volume (at least 1/3 bucket). Do not spend time testing new glazes if the day-to-day needs of running the studio are not being fulfilled.

When testing a glaze, mix only 100 grams or less of a glaze. That is enough to dip three test tiles. Do not make buckets of glaze. Share the results of all glaze tests -- test tiles and formula -- with the Glaze-Making Committee (leave copies in the committee chair’s cubby) to consider further testing. If the Committee agrees, a larger quantity (no more than 500-1,000 grams) may be mixed for further testing by studio members. No new glazes may be added to the established inventory without acceptance by the Committee.

Instructions for Ball Mill

When to use ball mill: mostly red glazes need ball mill, or any with Zinc Oxide as an ingredient.

• Mix glaze per regular instructions, but use a little less water as you will add some water when rinsing the balls later. Don’t sieve prior to ball milling.

• If mixing a full bucket, you will divide glaze between both of the ball mill containers.

• Pour glaze into the white containers. Fill only about ¾ full. More air in containers = better mixing.

• Put rubber cap on container. Use spoon to shoehorn it on.

• Squeeze metal ring to make it wider & put over rubber cap down to bottom ridge to hold cap on.

• Put ball mill containers on rollers. If only using one, remove other empty container.

• Plug in cord & turn switch on. Let it run for 45 minutes (it is very loud)

• After 45 minutes, take containers off, put sieve over bucket, and pour glaze out of containers & through sieve so it catches balls. Add a little water to rinse balls to get glaze off.

Balls need to be completely rinsed clean & put back into container when done.

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