Wood finish checking: The finish will check if it sets up
quickly and drying is too fast. This happens in the topcoat step
with both nitrocellulose lacquers and conversion topcoats. A
finish will also fail the ASTM cold check test if the topcoat is too
hard and lacks flexibility, or if the operator puts on too much
material (in excess of 3-4 wet mils per topcoat application).
Veneer vs. finish checks: Veneer and finishing checks are
sometimes confused. The visible difference is the consistency of
the checking pattern; a finishing check is much more random.
Trapping bad air/poor drying: As parts move through the
finishing stations, solvent- laden air may get trapped in the finish
and impede the cure. This can cause parts to become “gummy,”
resulting in sand-throughs, poor adhesion and rub throughs.
Pore bleed back: Wiping stains, fillers and heavy glazes may
bleed back through the pores of more porous woods, such as
oak, due to improper air. This finishing problem usually results
in a costly refinishing process drying and lack of clean make-up.
Fish-eyes/craters: The cause can be external or internal.
External: Lubricants and grease used for maintenance often
contain silicone, which can contaminate the finish, causing the
fish-eye/moon crater. The silicone can also come from hand
creams, soaps, and even deodorants used by employees.
Internal: Many clear wood finishes are formulated with some
silicone to enhance the slip or feel of the finish. If there is too
much silicone, fish-eyes or craters can appear.
Surprisingly, a way to remedy this is to use a corrective addi-
tive which has as its basic formula solvent and silicone. Made un-
der controlled conditions, the additive is different in its mixture.
The Importance of lighting
Colors appear differently under different light sources. Light
booths can be used to simulate the different lighting conditions
in a room, and help reduce project rejections.
Colors should be matched under daylight, which gives a true
view of the color and its hue, chroma, and lightness. Incandescent lighting shows colors to be “a touch” warmer and
redder than in daylight. Fluorescent lighting, while the least
expensive, is the worst light for color matching. Applied under
fluorescent lighting conditions, the finish will look green or yellow with a washed out appearance. While the reaction would be
to strengthen the color and make it warmer, if adjusted it could
appear too strong and/or too red in a home or retail store.
To ensure consistency, choose a finished piece as an accept-
able standard under daylight conditions and sign off on it. Keep
in mind brown tones may look slightly warmer or cooler upon
aging, so samples should not be kept longer than 6 to 9 months.
A longer version of the article appears online.
Source: Robert Cox Jr. is the former president and CEO of The Gilbert
Spruance Co. and Spruance Southern Inc. with 40-plus years industry
experience. He lives in Oreland, PA; e-mail: email@example.com.
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