Preparing the mask
Cut the sheet into individual PrecisionMasks
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Cut up the sheet of PrecisionMasks and the paper
underneath. The paper provides a useful support
whilst cutting and will then separate the masks from
each other whilst awaiting use.
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When cutting each mask, cut around the outside of
the 2mm pink border, leaving it attached to the mask.
Applying the mask
Float the PrecisionMask into position
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Dilute some of the adhesive concentrate - 1 part adhesive to 4 parts water (you may also store this diluted adhesive for use later).
- Ensure that the glass to be engraved (the "substrate")
is clean and free from grease or detergents.
- Dunk the PrecisionMask in the adhesive. For larger
areas, it may be advisable to wet the substrate with
adhesive as well.
- Place the wet PrecisionMask in position on the
substrate so that it is right reading. N.B. If you are
not sure which way up that is, the edges tend to curl
slightly away from the substrate side when wet.
If put into position straight away, the
PrecisionMask will tend to stay put. It can be made
to slide freely, however, if lightly moved with a small
circular "polishing" motion during application. N.B.
If one edge of the PrecisionMask is laid down first
and then the rest of the PrecisionMask is rolled
down onto the substrate, it will carry a pool of the
adhesive in front of it and thus avoid trapping bubbles.
Squeegee away the excess adhesive
- Wet a sharp edged squeegee with a little adhesive.
Gently holding the PrecisionMask in position, work
the squeegee out from the centre to the edges. At
first, press lightly and then progressively more firmly.
Squeeze out all bubbles and excess adhesive. Check
the final position. If need be, you can peel the
PrecisionMask off and start again.
Allow to Dry
- Leave to dry overnight in a warm, dry atmosphere.
Or force dry for around an hour in a low temperature
oven at 45 - 48°C, DO NOT EXCEED 50°C.
- When thoroughly dry, peel away the pink carrier film,
leaving just the blue PrecisionMask stencil film.
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- IMPORTANT: at this stage it is vital to check in case
you've left any bubbles under the PrecisionMask.
If you find any in the area around the image, mask
over them. If they are within the image itself, it is
likely that they will burst when they are blasted and
we recommend discarding this PrecisionMask and
starting again.
- Mask the surrounding area to protect it from
overshoot.
Blasting
- Shotblast to the required depth. Be careful not to
overblast and lose the finer details.
- IMPORTANT: Use the nozzle at right angles to the
workpiece.
- FOR HALFTONES: Do not attempt to cut any depth - this is a surface finish only. Depth will both wear away the smaller dots and generate additional reflections from the sides of the cut, spoiling the image. Using a fine grit, preferably one that is already well worn, a lower air pressure and, with the nozzle further away than normal (almost wafting the grit onto the mask), use a series of brisk, parallel passes, both across and up and down the image. This will help avoid banding.
Grit size
- A grit size of 320 or smaller is recommended. Larger sizes may break down the PrecisionMask too quickly. N.B. Most new grit is much sharper than grit that has been used for a while and may penetrate the fine detail PrecisionMasks at higher pressures, giving a very fine frosting effect on the substrate. Caution and a temporary reduction in working pressure is advised when using new grit.
Air Pressure
- Using a suction cabinet, a 6mm nozzle, an 8 cfm jet
and 320 grit, we recommend an air pressure of
around 60psi (4 bar) N.B. The effects of different
working pressures vary considerably from one unit
to another. Our best advice is to take it easy to start
with and gradually work up to whatever pressures
best suit your equipment.
Finishing
- Finally, soak in warm water to float the used
PrecisionMask off the substrate. The engraving is
now complete.
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