Effect of Heat on Sandblasted textures

This is based on Graham Stone’s work with float glass. The temperatures are applicable to float glass, and so need to be adjusted for other glasses, but illustrate the principle of how heating temperatures affect the glass.
Temperatures in degrees Celsius.

650 Blasted surface softened, evened, less "brutal".
690 Blasting still opaque but less "white"
700 Blasting becoming too sheeny but still okay for certain effects.
740 Blasting now subtle and glossy

Based on Firing Schedules for Glass; the Kiln Companion, by Graham Stone, Melbourne, 2000, ISBN 0-646-39733-8, p24

Antiquing Sandblasted Glass

Sometimes a sandblasted area appears too white when finished. One method that can be used to tone down the whiteness is to use low temperature glass stainers' enamel.

The low temperature enamels cure at temperatures between 530C and 580C depending on the type and manufacturer. At this temperature the glass is unlikely to change its shape. The jewellers and ceramics enamels fire at higher temperatures and are not suitable.

Rub the dry powder into the sandblasted area with a cloth or your fingers. The advantage of using the powder dry is that it will not stick to the smooth areas, although you may need to brush it out of any depressions in fused glass.

Fire the glass to the minimum temperature for the enamel, but for S96 or Bullseye try to stay below 540C. This temperature will fix the paint to the glass, but not change the shape of the sandblasting. Float glass will not change if you go to 580C. If you go to higher temperatures, you will go toward a satin effect and finally a smooth surface.

This technique has the advantage of being able to introduce a subtle colour tone to the sandblasted area. This enables you to match older glass that may have a slight colour cast from the glass or materials it has become encrusted with, such as nicotine.

This method requires testing to get the right levels of colour, and the temperature to balance the fixing of the enamel without changing the sandblasted surface beyond your choice. So you need to prepare several samples noting the amounts of enamel and temperatures used.

This has been successful for me when replacing broken sandblasted door panels that need to match the side lights. It removes the excessive whiteness of the new panel and can blend to match the colour of the originals.

Bottle slumping

Results

Devitrification is a major problem on bottle slumping. Some means of reducing the problem are

• clean labels off thoroughly
• remove all adhesives
• scrub the whole bottle and polish dry
• apply a devitrification spray before firing.
• Spend as little time in the devitrification range (700C – 750C) as possible
• Vent the kiln up to 540C if you are using fibre papers
• sandblast off the devitrification and fire again if the devit is slight
• in severe cases of devitrification, throw the bottle away.

Champagne and large bottles of sparkling wine split easily due to the differences in thicknesses. Firing of these needs to be very slow until you get past 715C.

Bottles with printed labels need particular care. The enamels used in the printing may contain lead and any other elements in the paint may contaminate your kiln.

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Resists

Avoiding bubbles between the resist and the glass on large sheets when preparing etching or other resist based processes is often difficult.

A trick learned from the firms that apply advertising vinyl to vehicles is to use a spray filled with slightly soapy water.

Their process uses pre-cut vinyl with an adhesive backing. So the first thing to do is to pick out the unwanted pieces. That is the pieces covering the areas that will be etched. Then you need to put a backing onto the front surface of the picked out vinyl – usually really wide masking tape.

Lay out the vinyl on the glass. Tape one end of the vinyl securely to the glass. This ensures that you get the vinyl correctly aligned over the whole area. Fold the whole piece of combined vinyl and backing back to the taped edge.

Carefully peal back the covering for the adhesive side making sure you do not pull off any of the isolated vinyl pieces. Spray the glass with a mist of soapy water to ensure all the glass is covered, do not have the glass running with liquid, but be generous. Too much liquid means that there will have to be a long wait for the vinyl to be firmly attached to the glass.

Start the application process by folding the vinyl onto the glass. Use a credit card or better, a large squeegee such as used for grouting mosaics. The tool you use must be smooth to avoid scratching the vinyl. Push the soapy water forward and to the sides as you move along the piece of glass. Keep pulling the protective layer evenly off the adhesive side as you work forward.

When completely attached, remove the backing from the vinyl. This will enable you to see any bubbles you may have left. Work out any bubbles by further pressing the soapy water out from under the vinyl to the edges. Where any remaining bubbles are in the way of the design, puncture them and work out the bubble of moisture through the hole. Cover the puncture with a small piece of vinyl.

Leave for a day for the vinyl to become firmly attached to the glass and then you are ready to do the etching.

Where you are going to cut the vinyl by hand, you do not need the backing. All the rest of the process is the same.

Resists for Large Areas

Avoiding bubbles appearing under the vinyl resist on large sheets of glass when preparing etching or other resist based processes is often difficult.

A trick I learned from the firms that apply advertising vinyl to vehicles is to use a spray bottle filled with water that is just soapy. A few drops per pint will be sufficient.

Their process uses pre-cut vinyl with an adhesive backing. So the first thing to do is to pick out the unwanted pieces. That is the pieces covering the areas that will be etched. Then you need to put a backing onto the picked out vinyl – usually really wide masking tape.

Lay out the vinyl on the glass. Tape one end of the vinyl securely to the glass. This ensures that you get the vinyl correctly aligned over the whole area. Fold the whole piece of combined vinyl and backing back to the taped edge.

Carefully peal back the covering for the adhesive side making sure you do not pull off any of the isolated vinyl pieces. Spray the glass with a mist of soapy water to ensure all the glass is covered, do not have the glass running with liquid, but be generous.

Start the application process by folding the vinyl onto the glass. Use a credit card or better, a large squeegee such as used for grouting mosaics. The tool you use must be smooth to avoid scratching the vinyl. Push the soapy water forward and to the sides as you move along the piece of glass. Keep pulling the protective layer evenly off the adhesive side as you work forward.

When completely attached, remove the backing from the vinyl. This will enable you to see any bubbles you may have left. Work out any bubbles by further pressing the soapy water out from under the vinyl to the edges. Where any remaining bubbles are in the way of the design, puncture them and work out the bubble of moisture through the hole. Cover the puncture with a small piece of vinyl.

Leave for a day for the vinyl to become firmly attached to the glass and then you are ready to do the etching.

Where you are going to cut the vinyl by hand, you do not need the backing. All the rest of the process is the same.

Glue Chipping, 2

Preparing the glass

The surface of the glass must be roughened up to allow the glue to adhere to the glass. This roughening is most often done by sandblasting the area of glass to be chipped. It can also be done by grinding the glass with grit between the glass to be chipped and another hand-held piece of glass. The grit should be at least 100 grit, and coarser is better.

After this roughening is done clean the glass thoroughly. Use raised masking tape to create a dam around the edge of your glass. This will keep the glue from flowing over the sides of the glass.