Resist Application Basics

Jun 2021 Author: Ghiath Khalil
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Resist Application Basics

Introduction

Applying the resist to the substrate is the most important step in the whole Sandblasting process. Not following these steps will cause damage to the item in the form of frosting due to lack of taping up exposed areas, blow out of centre of letters due to lack of cleaning the surface or releasing air bubbles with the wire wheel.

It is important to follow the steps to ensure consistent and efficient production.

CLEAN SURFACE

  • Ensure that the surface is clean before applying the resist to it. Use methylated spirits or glass cleaner.
  • If the surface is not clean the resist could lift when blasting and ruin the item.

TACKY RESIST

  • The resist is normally tacky when it is ready to use, always handle the resist from the edges so as not to contaminate the area being blasted.
  • If for some reason the resist does not feel tacky, its tackiness can be restored by applying the emulsion side to a cloth that has been lightly coated with water.

APPLYING THE RESIST

  • On occasions where necessary the substrate can be slightly heated to take of the chill, this allows the resist to adhere better.
  • Use the guide line in the artwork to help align the resist to the top/bottom of the item to ensure that it is straight.
  • On a curved surface (e.g. wine glass) draw a couple of horizontal lines on the glass to use as alignment points to ensure that the resist is straight.

BURNISHING THE RESIST

After applying the resist to our substrate we use a burnishing tool to remove air bubbles that may be trapped between the resist and the substrate.

  • We apply a little pressure with the burnishing tool to the resist to force air bubbles away from under the area to be blasted.
  • Burnishing also helps the resist to adhere well to the substrate.

REMOVING THE CARRIER SHEET

The carrier sheet protects the emulsion side whilst the film is being exposed, washed out, is drying, or being applied to the substrate.

Several ways of removing the carrier sheet:

  • Fold the film in one corner on itself and the carrier sheet will release, now peel the carrier sheet off.
  • With a pair of scissors trim a portion of one corner, burnish it down with the edge the burnishing tool, flick the edge of the carrier sheet to release it.

WIRE WHEEL

After removing the carrier sheet, you will notice air bubbles trapped under the resist. It does not matter if it’s away from the blasted area, but if it is where it is to be blasted (e.g. under centre of o, e, p etc.…

  • Use a wire wheel to perforate the membrane (the clear area) to ensure we avoid getting blow outs (centre of letter lifting).

    FINAL CHECK/MASKING UP

    Before blasting:

    • Check the resist is straight.
    • Check text/lines have not moved whilst working with the resist.
    • Check you have removed any air bubbles from the resist.
    • Check centres are still there after wire wheeling.
    • Tape up/mask any areas the resist didn’t cover that don’t need etching.

     

    In Summary

    • Always clean the surface prior to applying resist.
    • Always handle the resist by the edges.
    • Make sure resist is on straight.
    • Use burnishing tool to minimise air bubbles under the resist.
    • Use wire wheel to perforate air bubbles under centres of letters.
    • Final check before masking the area to be blasted to avoid frosting unwanted area.