SOP: Lacquer Adhesion Test (Scotch Tape Test)

GIFSQ — Global Institute for Food Safety & Quality

Principle

The truest adhesion check is to stamp can ends from the lacquered sheet and look at them. In the laboratory the scotch-tape method stands in: the lacquer is scratched with a fine needle, tape is pressed on, and ripped off. It reliably catches poor adhesion, though it cannot always separate good from middling.

Apparatus required

• (Gramophone) needle fixed to a handle weighing 100 g; steel scale; soft brush
• Scotch tape (transparent adhesive tape); smooth white card; flat support

Procedure

Cut out a test panel of lacquered sheet

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Fix the (gramophone) needle to the handle weighing 100 g; using the steel scale, make 50 scratches, 1 in. long, at 0.02 in. intervals on a suitable test area — the scratches should penetrate the lacquer film

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With the help of a soft brush, remove the grains of lacquer formed during scratching

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Firmly apply a piece of scotch tape to the scratched area with its length at right angles to that of the scratches, leaving one end unattached beyond the scratches

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Holding the test panel firmly on a flat support, pull off the tape with a sharp jerk

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Mount the tape on a smooth white card and assess the area of lacquer fragments detached — lacquer adhesion is considered satisfactory if the tape carries away no lacquer

Reference

Hoare, W. E. & S. C. Britton, Tinplate Testing, p. 41.