Martz Memories by Stanley Lee                                                             Tale # 10
Glaze mixing      Ball mills     Gerber jars     and Muffin trays


     A casual reader of some of these Martz tales might think we were forever mixing quarts of experimental glazes, only to discard uninteresting ones and make others.  Such a practice could be wasteful and would have been frowned upon by our pottery master, Karl Martz.   But there was a problem.  The time would come when a pot needed a glaze coat, and enough of a mixed glaze was required.  The capacity of the average spray gun container was about a quart, so for those who liked the smooth coating that came with the spray method, a quart of glaze was useful.  However, such a quantity was only necessary when glaze testing was over. 


     A first glaze test mixing was usually primitive.  Glaze ingredients were put into a mortar, and ground by hand with a pestle.  Water was added.  We mixed no more than could be contained in a four ounce jar.  A prepared food manufacturer named Gerber sold moist baby food in four ounce jars, and his product became a household word.  Mothers gladly gave us dozens of empty Gerber jars, and we used them as containers for test glazes.  A jar full of mixed glaze was enough to coat dozens of test tiles.  The jars sealed well, so the glaze moisture level of the test glaze remained constant through weeks of storage.  As a result, we used many Gerber jars. 


     Before a kiln load was fired to glaze temperature we wanted to prepare several test tiles to go into the kiln for firing along with other pottery.  To coat the tiles meant we had to bring our jars from storage lockers to the work table, and take them back afterwards.  It happened that a Silver Beauty muffin tray held eight muffins.  One tray would also hold eight Gerber food jars.  With three trays, stacked, I could safely carry enough jars back and forth.  I had solved a problem.

Adapt became our popular motto.


     The experimental mixes were suitable for tests, and four ounces of liquid glaze would be enough to brush-coat coat a small piece.  However, four ounces of glaze was not enough to use in a standard spray gun container.  A quart, yes.

 Could I adapt?  We did not have spray guns with smaller containers. 


     I thought of the principle the spray gun used.  Artists used the same principle.   Those who drew with colored chalks used a method with a simple sprayer that operated from air blown from the mouth, The air brought diluted gum from a hand held container, and made a spray to coat the fragile chalks.  Was there something that I could adapt?  I had lots of Gerber jars with lids l.  I also had an old air-compressor to provide a steady stream of air.  So, I soldered the necessary tubes in place on a lid, one tube going through the lid and down to the bottom of the jar which contained a liquid glaze.   It worked fine.  Voila!  I had a complete Gerber jar four-ounce container spray gun.  


     In practice, for mixing regular glazes, a ball mill was used.  Karl Martz made lidded, high fired, stoneware jars that held a gallon.  Some jars broke, so each competent student was expected to make one such jar during the semester.  With the glaze ingredients, water, and stones to aid mixing inside, the ball mill jar was sealed, placed horizontally to rest on two rubber rollers, and the mill motor switched on.  Glazes were mixed for half-an-hour.  The timing was standardized.  Long glaze mixing turned into grinding and the ground glaze could react to provide unexpected results.  We learned from Karl’s knowledge and disciplines, although we were invited to experiment, provided we recorded what we tried.  The watchful eye of the master was ever with us, but it was welcomed.  It saved us from mistakes before they happened.


     A gallon of new glaze was often more than enough for a student, but four ounces was rarely enough.  We needed an “in-between” ball jar.  What could I adapt?  Coffee-Mate jars?  Coffee-Mate was a popular cream-powder substitute.  It came in quart jars, and I had several empty jars.  I added pieces of rubber inner tubing for traction, and saw the jars would fit onto the rollers of the ball mill.  I still needed mixing stones.  A friendly gravel pit foreman showed me where I could find some.  With a bucketful of grape sized pebbles, I returned to try my quart glaze containers.   To my delight, I found that two quart jars would fit on the rollers at one time.  The system worked well, and I used it often.  Sometimes, I left a quart mill jar containing glaze and stones for weeks, but I always labeled the jars.  I had been taught to do so.     


     Thank you, Karl Martz.