Trouble Shooting

Trouble Shooting

 

Finishing problems require you to be a detective and investigate the exact cause or causes to know what the correct remedy should be. Usually, the causes can be divided into 5 stages based on when, where, and how often the problem occurs.

  • Wood Preparation and sanding
  • Condition of paint and proper choice of paint for purpose intended
  • Condition of application equipment, spray booth and general shop conditions
  • Defects appearing during or shortly after spraying
  • Defects after coating has initially dried or have developed on aging

It is our experience that 98% of the problems with finishes are not related to the paint quality but the misapplication of the paint for its intended use or the lack of technical knowledge of the finisher about the product or the equipment being used to apply the product. Therefore, an educated finisher is our most important job.

PROBLEMS WITH PAINT BEFORE USE OR IN PREPARATION FOR USE

CAUSES CURE

SETTLING OR PRECIPITATION (RESIN KICK-OUT)

Wrong thinner used If precipitation is slight, add proper solvent with constant agitation, or use stronger solvent.
Paint too cold Warm paint to 70-77F
Over reduction Add fresh paint to bring back
Reducer or catalyst added too quickly or without sufficient stirring Add slowly, and stir constantly
Pigment or flattening agent settled Check bottom of can with spatula or stick before using, and stir thoroughly
VISCOSITY OR HEAVY BODIED
Solvent in paint will evaporate at normal temperature and “body up” Use same solvent that manufacturer used to make paint. Check viscosity with cup
Used improper solvent Use recommended solvent for thinning
Catalyzed material beyond paint life                                                         See directions-some products can be recovered by adding additional paint and catalyst
SKINNING OR GELLING IN CONTAINER
Air drying material that is exposed to air is partially full Float thinner on surface of pail and seal it, make sure container is sealed or put in new can
Gelled material Usually cannot be recovered and must be discarded.
Stored at high temperature, outside, or beyond product’s shelf life Store inside at room temperature and use before 6 months if polyester, polyurethane, or pre-catalyzed lacquer.
DISCOLORATION OR FLOATING PARTICLES
Presence of vapors or fumes in spray area Investigate fumes like ammonia or amines from adhesives or other sources
Water born or acid cure react with steel parts or oxidize aluminum spray equipment Use stainless steel or solvent resistant plastic parts and liners for spray pots
Improper drum or pail lining comes off Strain paint through fine filter or cheese cloth
Old nitrocellulose products Become amber on age in can or react with steel. Use fresh material
Chemical reaction to surface treatments Check pH of surface since acid cures can react with alkali materials
FOAMING  ( WATER BASED)
Mixing too rapid Mix slowly; do not shake with mechanical shaker
Foam trapped in container Use defoamer recommended
DEFECTS OBSERVED DURING APPLICATION
CAUSES CURE
DIRT OR SEEDINESS
Unclean conditions such as dust in spray room or drying area, dirt in air or paint line, sanding operation near air in-take of both Check air supply for oil and dirt by spraying air only from spray gun at white cloth or tissue and look for staining or dirt.
Resin kick out from improper thinner Use correct thinner
Paint is very cold and created seeds Warm material to room temperature
Dirt in paint Strain paint before use
Particles appear after spraying but not while spraying the wet film Make sure with magnifier that it is not air bubbles. Dip or pour paint on glass and let dry in enclosed dust free area. Examine film when held up to light for defects.
DRY SPRAY
Wrong solvent used Choose slower evaporating solvent
Spray gun problems
Atomized air pressure to high Lower air pressure
Gun too far from surfaceSpray past surface-bounce back of spray Hold 6-10 inches and at right angles to surface,  release trigger when gun passes target; check that spray booth is sucking out overspray. Increase fluid pressure and check by cutting off air to gun and adjust stream of paint  to fall approx. 3 ft. from gun if gun at shoulder height.
Fluid pressure too low  
Wrong air cap or fluid tip Use correct combination based on manufacturer’s guide
ORANGE PEEL
Paint not thinned properly Use correct amount of thinner and slower evaporating solvent
Spray gun problems
Stroke to rapid or at angle Slow stroke and at right angle to work
Air pressure too low Increase air pressure
Fluid pressure too high Decrease fluid pressure
Spray gun too close or too far from surface Distance should be 6-10 inches from surface
Air temperature too hot Use retarder solvent
Overspray striking wet surface Avoid creating over spray or spray so that it does not strike previously spray surface
SAGGING
Over-reduction of solvent is too slow Use proper amount of thinner and faster solvent
Paint applied too heavy Apply thinner coats and more passes to get film build.
Cold weather or no air circulation Use faster thinner or raise room temperature
Gun too close to surface Hold gun 6-10 inches from surface
Fat edge Spray edges first with thin coat, then spray piece.
FLOW OR LEVELING
Paint too heavy Reduce to correct viscosity and check with Zahn #2 Viscosity cup.
Solvents evaporate too fast Use slower solvent if higher air temperatures
Improper air atomization Adjust spray gun
Application too thin Apply material to surface by using more passes, wet on wet.
Too much air movement Reduce draft
DEFECTS OBSERVED DURING OR AFTER CURING
CAUSES CURE
POOR ADHESION (TO SUBSTRATE)
Unclean surface or oily wood or stain Clean with VM&P solvent and avoid oil base stain
Primer or sealer lifts from surface Make sure recommended sealer and top coat are used
Wood sanded too smooth especially close grain hardwoods Use 120 grit sandpaper on close grain and 120-180 grit on open grain or soft woods.
Stain comes off with sealer Apply thinner coat and wipe stain off
Stain applied too heavy or not wiped and did not dry Be sure stain is dry before applying sealer
Higher solids coating used as sealer High solids need a better profile to anchor. Avoid polishing wood when sanding and use 120 grit.
POOR ADHESION ( INTERCOAT)
Primer or sealer contaminated Clean surface
Sealer or primer sanded too smooth Sand 220 to 280 grit maximum
Catalyzed finish dried too long between sanding and recoat Check recoat window of paint and sand within 8 hours of top coat application
Sealer and top coat not recommended Use only recommended system, avoid using supplier’s sealer and another’s top coat.
BLEEDING
Organic reds, yellows, oranges used in stains have not been sealed properly Avoid bleeding colors; Use vinyl sealer to seal to stop lacquer top coat from causing bleeding. Check Japan colors do not contain bleeding pigments or dyes.
Certain woods contain tanins that bleed Seal with barrier coat.
BLOOMING
Oil from wood or stain floats to surface Use barrier coat to seal in oil.
BLUSHING (WHITE HAZE IN FILM )
Humid weather above 60% humidity Add up to 16 fl. oz. retarder solvent in place of thinner
Paint sprayed cold Bring to room temperature
Moisture in spray equipment Check air line for moisture; compressor should have air cooler to prevent water condensation.
BLOCKING (OR PRINTING)
Insufficient drying time before packing Allow longer drying time or use heat
Too heavy film causing solvent entrapment  Apply lighter coats or multiple passes
Poor drying conditions Change conditions by using heat or forced air
Improper catalyzed material Check measurement of catalyst
Catalyzed material beyond pot life Follow recommended time to use after catalyzed
BRITTLENESS
Paint over catalyzed Check measurement of catalyst. A good indicator may be a shorten pot life
Paint baked at high temperature Check recommendation of manufacturer
Paint not formulated for wood Paint for metal are harder but do not have elasticity of coatings formulated for wood.
CRACKING
CAUSES CURE
Excessive dry film thickness especially with acid catalyzed materials Use wet film gage during application. Do not have a dry film thickness of more than 4-5 mils with acid-catalyzed materials or pre-catalyzed  lacquers.
Grain or veneer cracking Cracking following grain shows wood is cracking and not caused by the paint
Cold cracking by repeated cycles of freezing and return to room temperature Paints are normally formulated to resist 10 cycles. Put painted wood in freezer for one hour and return to room temperature for an hour and repeat 10 times to see if fresh paint will crack.
CRATERING
Film pulls away from areas of substrateCratering caused by contamination from silicone, wax or oilIf no cause can be found Find source of contamination in sanding aids on belts that may contain silicone or lubricants or oils or greases for machines or spray equipment, hand creams, or polishes as possible sources and eliminate their use by finding substitutes. You can use anti-cratering additive but silicone will continue to cause equipment contamination and higher amounts of additive will be needed.
DRYING TIME
Humid weather Use heat or reduce humidity
Cold weather Drying area should be at room temperature
Oily or unclean wood Clean wood by solvent wipe or use barrier coat for oily wood.
Oil stain prolongs drying Use non-oil base stains
No air movement Use proper ventilation
Trying to fill open grain wood with heavy coat of sealer which traps solvent in pore Use filler or high solids sealer like polyester or polyurethane to fill pore.
GLOSS CHANGES OF FLAT SPOTS
Absorbent putty or filler that has not been sealed causing top coat to “strike in”. Seal wood filler or putty.
Not enough sealer used or sanded through allowing top coat to “strike through”. Carefully sand especially around the edges and corners.
Material from same container changes gloss or after a few hours of spraying changes Stir material at start to be sure it is uniform. Stir after several hours if highly pigmented or high amount of flattening agent was used which is causing settling in can to occur quickly. 
Gloss increases with successive coats. The smoother the finish after sanding, the glossier it looks with more coats.
HAZING
Incorrect thinner Use thinner recommended
Over catalyzed with acid Resand and recoat but test inter-coat adhesion.
Blushing See remedies for blushing
Water mixing with paint because of air Clean air line separator and bleed the line once per shift.
HIDING
Over reduction Add more paint
Pigment has settled to bottom of can Stir before using and check for settling. Low film build. Apply more paint with more passes
Edges show through Edges are too sharp so round edges by sanding
Color does not match standard-base color is showing through top coat Apply more paint to achieve full hiding; Color base coat same as top coat for extra hiding; organic pigments have poor hiding and require thicker film.
MARRING
Film not completely dry Allow more days for drying before put in use
Emulsion base does not coalesce below 55F and will not cure Apply at proper temperature
Acid and polyester coatings will not cure at low temperatures. Must cross link at manufacturer’s recommended temperature range. They usually take 7 days to reach final hardness.
Pot life has expired Must use within pot life or may be able to reactivate with fresh material and catalyst.
Soft film Mar resistant additive may help but use proper system for intended use. Don’t use nitrocellulose lacquer if you want a hard scratch resistant film.
PIN HOLING (BUBBLING)
Water in air atomized Clean air separator and drain water from line
Air trapped in open pore of wood Use a thin wash coat to penetrate pore
Fine bubbles after force drying Use adequate flash off time before using heat
Polyurethane bubbles carbon dioxide causing pin pricks to appear after drying Urethane reacting with moisture: use retarder and successive thinner coats.
Viscosity too heavy trapping air Thin paint 
Film too heavy Use thinner coats
SHRINKAGE (WRINKLING)
Surface dries quicker while underlying paint remains wet causing wrinkling Avoid excessive heavy coats. Force drying may cause wrinkling. Polyester primers shrink if sanded to soon even if dry. Allow overnight cure before sanding
Incompatible coating systems-solvent in top coat attacks and softens primer. Use compatible systems and follow manufacturers recommendations
YELLOWING
Exposure to UV in sunlight Use UV inhibitor in coating or correct paint
Yellow on aging All coatings yellow, some more than others, aliphatic polyurethane’s and acrylics yellow least; nitrocellulose lacquers, aromatic urethanes, oil drying alkyds conversion varnishes yellow more.
Exposure to strong amines Some coatings yellow more when exposed to ammonia or other amine cleaning agents.
Yellow blotches or brown spots. Yellow spots can be caused by bleeding dyes or such as hansa yellow coming to surface or oils causing staining.