When our group ran into this issue, I suggested using a trick I had picked up back in my undergraduate days at Buffalo State College. At that time I was applying multiple glazes to each pot using a spray gun, and was dismayed at how powdery the freshly sprayed glaze was. Sprayed glazes tend to be very porous, powdery, and easy to rub off your pots. Some of the glazes I was using were so sensitive that fingerprints from where I handled the pot would show up after the cone 10 firing. One of the other students suggested using spray starch (1)—commonly used for ironing, and available at any grocery store.
The spray starch, when applied in an even coat and allowed to dry, creates a hard surface that protects your glaze (2–3), but burns off in the kiln, leaving no trace behind (4). (Another variation on this trick is to use liquid starch, also available in the laundry section of your local grocery store, and mix it into your bucket of glaze—this will get moldy so mix it in small batches. If it does mold, just skim the mold off and stir well. Any remaining small traces of mold will burn out in the kiln.)
More recently, I started using underglaze pencils to add some line work to my functional pieces, but was having a hard time with the powdery pencil marks easily smearing. I decided to experiment on one of my class demo pots, and see if the spray starch would also work under the glaze, fixing the pencil in place so I could paint on clear glaze with worrying about smearing. It worked like a charm. The pencil didn’t smear, and the starch burned off in the kiln, with no side effects (5).
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