Sandblasting Resists - A New Approach

Transfer printing as a mask for abrasive (sand) blasting.

Research by Bev Butler.

he usual method for sandblasting is to use adhesive tape or sign writers' vinyl which has had the design cut by a computer program. My method gives a softer effect, is easier to prepare and looks quite different from the taped and cut images. I first used this method to protect areas of lustre on stoneware fired pieces. Lately I have been using the same method to texture raw dry surfaces.

Stoneware, bronze glaze, Acid etched, raw sandblasted

Using the transfer printing technique screen print several sheets of lunch wrap or tissue paper with your design. Cut as required and transfer the resist ink onto the surface of the pot. This acts as your sandblasting mask. On a fired surface the transfer ink remains sticky and during the blasting collects a layer of grit which helps protect the the surface further.

• Sandblasting will not work well on damp surfaces. By using the slow drying transfer ink you will create a temporary barrier on a raw dry surface giving you ample time to complete your sand blasting.
• Bolder designs will be more resistant than fine lines.You have no time limit if you are preparing a resist on a glazed fired piece, but with raw ware only work on one piece at a time.
• For sandblasting on white clay, use kaolin or ball clay and colour with a bright child's powder paint. These paints have a vegetable dye and no oxides and all colouring will burn out in the firing. If your clay surface is a terra cotta or buff clay, left unglazed or to be covered with a transparent glaze, you may need to make your dry clay component from your clay body.

Sandblasting is a filthy habit and could be a health hazard, but this doesn't seem to worry some potters. The sand blasting grit is bad enough, but when it is coupled with powdered dry clay in great volume - you need protection. We're not talking just a dust mask and a dust jacket. You really need some sort of sealed protective booth. Cost was a major factor and I could not justify the purchase of a commercial sealed blasting booth. I have a side opening wooden, glass fronted cupboard as a booth with a light and a large Burwell extraction unit attached to its side. ( I used a large vacuum cleaner initially). My hands are protected by gloves as in a commercial booth and I still wear a mask while I'm sand blasting.

Don't be tempted to use a spray gun, as a sand blasting gun is quite different.

My gun is a cheap $30 unit, which needed a little modification as there was not enough air space around the intake tube. If your system won't pick up the abrasive material efficiently check the air space gap between the intake metal tubes. By increasing this space (I doubled the space with a larger outer tube) you may solve the problem.

A ceramic sand blasting nozzle can cost $25 and depending on your blasting pressure a solid day's work can really chew one about. By saving the rubber washer from your original nozzle you can replace this nozzle with a piece of stainless steel pipe for less than a dollar. Your new nozzle will give you approximately 80% usage time compared to a new ceramic nozzle. Use a low pressure 40 (max 80). This will also give a longer life to your sand blasting nozzle

Your grit is important. There are many different metal abrasives, as well as plastic and even crushed walnut shell. Forget sand, it's illegal and more of a health hazard. After a lot of experimentation I now use Garnet or 80 mesh aluminium oxide (not a pottery supply item) purchased by 20 kg bag from Burwell Abrasives.Be cautious, complete one small section at a time. Let the dust clear and continually check your results. It can't be done in a rush, especially when blasting raw clay. 80 PSI is my maximum pressure, and a great saver of nozzles. I drop back to 40 PSI when working on lustred surfaces.

Transfer print texture, raw clay sandblasting

Bev Butler. Tel (02) 6568 1729