What is fish eye and How this problem can be solved?
- Fish eye, also known as CRATERING or CISSING, is type of defect that has the appearance as small crater in the paint film and can either occur during the spraying or immediately after. A contaminant is breaking surface tension of a wet paint film so that the paint film pulls away from the contaminations causing a depression in the film. There are lot of contaminants:
- Contaminants on the vehicle:
a) Residue of protective transport wax on new cars.
b) Silicon wax polish on older cars.
c) Use of silicon containing glazing adhesives.
d) Poor processing:
- Residue of soap from flatting water.
- Dirty cloths used for spirit wiping
- Grease / Oil from overalls or hands.
- Transfer of resin from oversticky tack cloths.
To avoid these types of contaminant always clean the vehicle thoroughly using degreaser prior to starting any work and always clean before the application of any paint.
- Airborne Contamination
a) The use of wax polish in the vicinity of the spraybooth.
b) The use of silicon containing lubricants in the vicinity of the spraybooth.
c) Minute quantities of silicon in sanding dust.
- Contamination of the compressed air
A small amount of oil in the compressed air line is a common cause of cratering. This may sometimes be identified by the presence of a faint brown ring around the circumference of the crater
-Contamination of the paint mix
There are various anti-cratering additives available in the market and the majority of these additives contain silicon. Missuse of these materials can cause cratering and contamination of the spraybooth giving cratering problems on subsequent jobs.
RECTIFICATION:
The correct method for handling cratering problems is to identify the source of the contamination and then eliminate it. If the defect is severe the best is to stop painting and allow the paint to completely dry. Once the paint film is thoroughly dry, clean the surface using degreaser. Flat the paint film until all evidence of the defect has been removed, clean and dry, and very carefully degrease and repaint.
