Painting Defects

BGAS Painting Inspector Exam Painting Defects Name and Definition

Banding

This defect is found in spray applications where there is heavy application of paint on the outside of the spray pattern with little paint in the canter of the fan.

The cause can be:

• Too much air pressure
• Uneven lapping of the spray gun
• Having the gun too close to the job

The remedy may be found from:

• Use at correct air pressure
• Ensure that the overlap of each stroke is 50% over the previous coat
• Hold gun at the correct distance from the job - about 15 cm for lacquers and 25 cm for enamels. To correct a coat that has been applied, re-coat with double coat using thinner that has been specifically recommended for the paint using indicated solvent ratio and pressure, and ensuring that the gun is held at the correct distance.

Bleeding

This is the migration of the color from a previous coat into the freshly applied top coat. This defect usually occurs when a light color is applied over a dark color, particularly reds and maroons which are prepared by using organic pigments not resistant to solvents or application over a surface contaminated with bitumen where the solvents in the fresh paint dissolve the bitumen.

The remedy is:

• Use a bleed sealer before application of the light color
• Wash the surface with mineral turps if it is contaminated with bitumen.

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