Compilation of Causes and Solutions for the main Problems or Defects that we may encounter during the Wood Varnishing process

varnish defect problems

List of defects in varnishing

During the varnishing process we may encounter some problems or defects. Here, we try to collect some of the most common problems, the causes that originate them and the possible solutions or remedies for the problem.

Boiled or bubbles – Ambient temperature too high.
– Very light thinners.
– Pieces in the sun.
– Drafts.
– Very fast application of the second hand.
– Use a slower diluent (DTE. Retardant).
– Drying parts in the shade.
– Avoid drafts or excessive air speeds in the drying tunnels.
– Wait a pre-drying time before applying the second coat (let the solvents of the first coat penetrate).
Wrinkled – Applying a second coat without the previous one being hard enough.
– Poorly catalyzed anterior layer.
– Respect the drying time of the previous layer, especially in winter.
– Respect the mixing ratios.
Rejections (fisheye) – Traces of fats, oils, silicones on parts or application material.
– Contaminated compressed air.
– Identify the source of contamination and eliminate it.
– Complete cleaning with cleaning thinner.
– Bleed the compressor.
Veiled – Very high humidity.
– Use of very light or inappropriate thinner.
– Check the compatibility of the diluents used.
– Spray a thin layer of retardant thinner (for nitrocellulose).
– Add retardant thinner to the varnish (5% nitrocellulose and pre-catalyzed).
Does not dry the product – Missing or missing component.
– Very slow thinners.
– Check that the mixture is correct.
Poor adherence to the support – Wood resin residues.
– Treated wood (stripper, fungicides, etc …).
– Wood waxes, etc …
– Degrease the wood with cleaning thinner before varnishing (even if completely peeling if necessary).
Poor adhesion between coats – Wax between layers.
– Interval between coats too long without intermediate sanding.
– Non-repainting product used as pre-coating
– Remove or sand the applied layers.
– Do not wait too long to apply between coats (but sand carefully).
– Observe the compatibility notes
Roughness, grain – Dirty air, dust.
– Poorly repaired bottom.
– Dirty material.
– Excessive air pressure in the application.
– Very thick product.
– Filter the air.
– Sand the bottom well.
– Remove the material.
– Reduce air pressure.
– Dilute the product according to the product instructions.

Obviously, here are not all possible problems and causes, only those that occur most frequently when applying the different types of varnishes.

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