Troubleshooting
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 | Spray gun problems |
| Atomized air pressure to high | Lower air pressure |
| Gun too far from surface Spray 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 | 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 | |
| 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 substrate Cratering caused by contamination from silicone, wax or oil If 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 | |
| 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 | SYellow spots can be caused by bleeding dyes or such as hansa yellow coming to surface or oils causing staining. |
Troubleshooting Guide and Application Guide for Plextone® Multi-Color Finishes
| Problem | Cause | Correction |
|---|---|---|
| Sagging |
1. Too high pot pressure Too low atomizing pressure 2. Gun too close to surface 3. Spray motion stopped before releasing 4. Excessive thinning |
1. Lower pot pressure Raise atomizing pressure Maintain 5-10# differential 2. Hold gun about 18-24 inches from surface 3. Continue spray motion after trigger release 4. Add unthinned paint |
| Merging Particles |
1. Too high atomizing pressure 2. Blocked nozzle 3. Material too heavily bodied |
1. Lower atomizing pressure below pot pressure by 5-10# 2. Remove and clean nozzle 3. Add 5% water and “box” material |
| Spray Gun Clogging |
1. Gun dirty 2. Material too coarse for tip |
1. Clean gun 2. Strain material thru coarse strainer by gravity only |
| Elongated Particles |
1. Arching wrist motion 2. Material too cold 3. Air pressure too high |
1. Move gun parallel with surface at a distance of 18-24 inches 2. Warm material to 70°F 3. Lower pressure |
| Streaks |
1. Excessive “triggering” of the spray gun 2. Insufficient of improper overlapping of strokes |
1. Retain trigger pressure throughout stroke 2. Use cross strokes |
| No Paint from Pressure Tank |
1. Insufficient air pressure from compressor 2. Leaking pressure tank cover gasket 3. Clogged Lines |
1. Check compressor pressure 2. Replace gasket 3. Lubricate for use |
| Paint Leaks from Spray Gun |
1. Damaged fluid tip or needle 2. Dried particle blocks fluid tip 3. Packing for fluid needle dry |
1. Replace tip and needle 2. Remove tip and clean with mineral spirits 3. Lubricate for use |
| Pattern too small compared to standard |
1. Over atomization (too much air) 2. Clog in fluid nozzle restricting material |
1. Decrease air or increase fluid pressure 2. Shut down system. Remove fluid nozzle and clean |
| Pattern too large compared to standard | 1. Under atomization (too little air) | 1. Increase air or decrease fluid pressure |
| Pinholing or insufficient coverage |
1. Moving gun too fast 2. Too little air |
1. Slow down 2. Increase Air |
| Cobwebbing or stringy |
1. Material cold 2. Pressure too high |
1. Warm material 70°F 2. Lower pressure |
| Primer showing through on coarse texture | 1. Large particles require more film buildup | 1. Use base coat/pattern coat spray technique |
| Gelled particles or paint |
1. Paint has probably been subjected to high temperature exceeding 100°F 2. Paint has probably been subjected to freezing temperature |
1. Material is probably not usable 2. Warm material to 80°F to see if gel disappears. If not material is not usable |
| Color Drift/Pattern change while spraying |
1. Pressure changed while spraying 2. Not properly mixed causes phase separation 3. Changed lot numbers |
1. Adjust pressure 2. Mix properly by boxing 3. There are variations from batch to batch. Complete wall or total surface with same batch |