The resist lines around the quail, leaves, rose and stick define the shapes from a distance. They also separate glazes which might react in unusual ways if they came in contact with one another. I experimented with two traditional techniques before settling on a modern solution. The first technique I tried was melted beeswax from my Ukranian egg decorating supplies. The lines came out clear and fine and the wax did an excellent job of separating the glazes. The process was too time consuming for the scale of project I had in mind. I couldn't spend an hour on each tile before even starting to glaze.
Next I tried painting on a mineral pigment suspended in oil. Traditionally, this has been done with manganese. I didn't want to invest in powders I might not be using, so I tried it with iron oxide powder. The results were mixed - some samples had clean, dark lines bonded to the tile. Others flaked a bit. But the application of the suspension with a brush was uneven and, again, too time consuming. At the Malibu Potteries in the 1920's and 30's, the pigment was silscreened on each tile. This works well if many tiles are the same, but too many of mine were one of a kind for screens to be practical.
After some web searching, I tried
a modern wax resist emulsion from Aftosa. I also ordered small 2 ounce
squeeze bottle and fine-tubed metal caps to apply the resist and the glazes.
This has worked well, after a bit of playing around to figure out how to
keep the resist from coming out too fast. The trick is to expel some air
and maintain a slight amount of suction in the squeeze bottles so that
the glaze or resist won't flow out by gravity. The resist cleans up with
water but dries to become water resistant. I found it worked best to let
the resist dry for a day before glazing, or at least for a couple of hours
until it became transparent.