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PAINT TROUBLESHOOTING GUIDE

FAULTS - CAUSES - PREVENTION


PAINT NOT DRYING

Causes:

• No or insufficient catalyst / hardener added
• Incorrect thinner used / make sure thinner contains no methanol • Water in the air lines
• Extreme cold temperatures
• Excessive wax in the MDF board, aggravated by excessive film weights
• High application viscosity

Prevention:

• Make a new mix with correct catalyst / hardener ratio
• Ensure thinner is correct
• Clear water traps
• Check temperature of the paint, should be above 10-12°
• Use of Isolation sealer onto raw MDF board prior to primer coats (see data sheet)

DRY SPRAY

(Rough finish on the surface)

Causes:

• Viscosity of the paint is too high
• Air pressure is too high
• Use of a very fast or poor quality thinner
• Poor spray technique, gun held too far away from the substrate
• Dirty and or blocked spray equipment

Prevention:

• Reduce the viscosity with a good quality thinner
• Reduce the air pressure
• If spray conditions are poor, add a small amount of retarder thinner
• Check that spray equipment is clean and in good working condition

BLUSHING

(Milky appearance in the paint film)

Causes:

• Excessive humid and or rainy conditions
• Use of a poor quality thinner
• Thinner is too fast
• Cold spray conditions with lots of air movement in the spray booth
• Check for water / moisture in the airlines

Prevention:

• Ensure spray booth is adequately heated
• Use of a good quality thinner
• Add retarder thinner in small amounts for severe conditions
• Check water traps are clear of excess water
• Install water traps on airlines

SOLVENT RASH, PIN HOLEING / BUBBLING

Causes:

• Very hot conditions / excessive air movement over the work surface
• Air pressure too low
• Application of excessively thick films
• Insufficient flash off times between coats
• Viscosity too high Use of incorrect or cheap thinner

Prevention:

• Use correct air pressure
• Check viscosity 16-18 sec for normal rule of thumb, this can change with application equipment and type of lacquer
• Do not apply excessive coats without adequate flash off times
• Check oven temps and air flow
• Use correct /recommended thinner
• Add a good quality retarder thinner If the problem continues use 1-2 % by volume of paint of bubble breaker (149 – 0003)

CISSING / FISHEYES

(Often caused by outside contamination, silicone sprays in the work area)

Causes:

• Contamination of surface by wax or silicone polish, oil or grease
• Overspray of a different paint type
• Oil in the air line
• Contaminated work surface, machines or sanders sprayed with silicone
• Dirty / greasy hands contaminating the work surface
• Contamination of the paint or thinner
• Often water in the thinner

Prevention:

• Clean all surfaces thoroughly with something like benzine
• Sand the surface again and clean with benzene before next coat
• Check that your thinner is not contaminated, i.e. water Excessive Water will always be at the bottom of the container
• Do a fresh mix of paint and thinner
• IF problem still exists then add 1% of an anti-fisheye solution (116 – 9003)
• For repairs on old furniture, use isolation sealer

CRACKING

(One of the more serious of paint problems as they often appear once they leave the factory often only after 3 weeks and more)

Causes:

• In the case of coating MDF board, not using isolation sealer to control wax from the MDF board been absorbed into the paint films (see isolation sealer data sheet)
• Excessive film weights especially on the edges of the board
• Incorrect hardener / catalyst ratio’s and not stirring the catalyst paint thoroughly before spraying
• Poor quality thinner
• Applying numerous coats without allowing adequate drying between coats

Prevention:

• Use of isolation sealer on the MDF and taking special attention to the edges
• Do not apply excessive film weights and allow adequate drying between coats
• Make sure correct quality thinner
• Check that the correct catalyst / harder is been used and in the correct quantity
• Mix paint and catalyst / hardener thoroughly before adding thinner then stir the complete mix well

ORANGE PEEL

(A rough eggshell finish)

Causes:

• Paint viscosity is too high
• Poor grade solvent and solvent are too fast evaporating
• Air pressure too high or low
• Application coats too thick or thin
• Poor spray technique, too far or too close to the job

Prevention:

• Reduce paint viscosity with correct solvent
• Adjust air pressure to suite application and paint systems
• Check your spray technique
• Check needle / tips for wear

VISCOSITY

Causes:

• All Catalysed paints increase in viscosity after catalysing causing numerous problems
• Ambient temp affects viscosity

Prevention:

• Check viscosity regularly, especially when using PU Lacquers
• Use a good viscosity cup and always keep it clean
• Ensure containers are covered when possible and closed when not used

GLOSS LEVELS VARIANCES

Causes:

• Lacquer not stirred adequately
• Viscosity too high or low excessive coats / film weights
• Incorrect catalyst ratios
• Poor quality thinner

Prevention:

• Ensure correct catalyst ratio / thinner and stirred well
• Check viscosity is in correct spec for application Remember that it takes 48 hours for gloss levels to stabilize