First, some background by Karen Murphy...
After years of procrastination, we finally decided that there would be no perfect time, nor place. The First Annual Polymer Clay Teachersí Retreat, hosted by Karen Murphy and organized by Lindly Haunani took place the third week of August, 1999. There were 17 talented and enthusiastic teachers present--yet only a fraction of the teaching community. The following is a summary of our focus discussions...
There were 6 discussion areas:
SANDING - Linda Goff:
Use Wet/Dry sandpapers which can be used with water. Sanding sponges and sanding films with plastic backing are also available. Some brands of emery boards are similar to sandpaper.
Sandpaper comes in numbered grits, with lower numbers being coarser than high numbers. The numbers correspond with number and size of grit per square inch.
Hint - The surface of ordinary brown grocery bags is similar to 400 grit sandpaper.Start with as coarse a grit as you need and water, then use progressively finer sandpapers until you achieve the desired surface. Each grit of sandpaper removes scratches from the previous coarser grit. Most of the time 600 grit is high enough unless you want an absolutely silky finish.
Keep your piece and your sandpaper wet and rinse frequently with clean water. Sand in a circular motion - do not always sand in the same direction. Remove sanding sludge from any crevices before re-baking or it will bake into the clay permanently. Faster sanding is possible by partially baking your piece at 210-220 degrees for 15 minutes, then sanding. Support your piece very carefully since partially baked clay is soft and fragile. 400 grit sandpaper cuts partially baked clay like 320 grit cuts fully cured clay. Sand up to 600 grit, make sure all sludge is removed, and rebake for the normal time and temperature. Baking will remove sanding marks. A light sanding can be done after baking.
Bolt your bench grinder to a stable surface. Put an open box behind the wheel to catch buffing residue. Wear a mask - buffing produces lots of fine dust.
Tie your hair back and remove any loose dangling jewelry. Tuck in your clothes. Wear protective eye gear - the buffing wheel is capable of snatching things out of your hands and flinging them away at a high speed.
If you drop something, turn the machine off and wait till the wheel stops before bending over to pick it up. Do this even if two people are buffing at the same time. Itís better to inconvenience your partner than get something caught in the wheel.
If you follow safety rules, buffing should go smoothly. Use either unstitched muslin or a cotton flannel wheel. Use bare wheels, no buffing compound.
Set your wheel at about medium speed. Grip your piece firmly and place it lightly against the lower front quadrant of the wheel. Use a gentle circular motion, keeping the piece moving and making sure all of the surface is buffed evenly. If you press too hard into the wheel, it can cut grooves into your clay and friction heat can begin to melt the surface.
Hint - Some people buff clay work on their jeans instead of using a buffing wheel.Portable buffers such as DremelTM tools are available if you are not ready to purchase a jewelers buffing wheel. Most bench grinders without variable speed are too fast for polymer. Variable speed control is important.