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Performing
quality touch-up work can be difficult and in some cases impossible.
The reason why effective touch-up work is so difficult to achieve is
due to a discrepancy in porosity of the substrate and the existing
coating.
Any freshly damaged areas will absorb the touch-up coat at a different
rate than the surrounding areas that had been previously painted;
resulting in variances in color and gloss (also known as “Flashing”).
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Touch-up work
showing flashing.
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Although
touch-up work may not be possible in every situation, the list below
provides a general set of conditions that typically must exist to
effectively touch-up a surface.
5 Conditions
for Effective Touch-up Work
1) The
existing coating should have an MPI Gloss
Level of either GL - 1 (a traditional flat finish) or
GL - 2 (a traditional matte finish):
Coatings with higher gloss levels will be too difficult to touch-up.
Variances in light reflectance are significantly more noticeable with
higher gloss paints.
2) The
existing coating should be light:
In general, deeper/darker colors are more difficult to touch-up
effectively.
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3) The surface
must not be exposed to critical lighting conditions:
Even if the existing coating is an MPI GL - 1, touch-up work can appear
visible under critical lighting conditions.
4) The same
batch of paint must be used for touch-up:
Different batches of paint will have slightly different qualities even
though they are the same product from the same manufacturer. Even the
slightest variance in color and sheen is noticeable when it appears
side-by-side in the middle of a wall. In general, it is a good idea to
keep a little bit of paint left over for touch-ups.
5) The same
type of application tool must be used:
Different application tools will provide different finishing textures,
and will ultimately make any attempts at touch-up work visible. If the
initial coating was applied by a roller, the touch-up work must be performed
with a roller with the same nap size. Using a 10-mil nap roller to
touch-up a surface that was applied with a 15-mil nap roller will
create a significant variance in texture.
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Brush marks
from touch-up work plainly visible on a rolled wall.
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If the surface
in-question meets all 5 conditions listed above, there is a good chance
that effective touch-up work will be possible.
Keep in mind that while the list above does not guarantee whether or
not a surface can be touched up successfully, it does provide a general
set of conditions that are typically required for effective touch-up
work.
Whether a surface can be touched up at all depends on a range of
factors including the finish’s gloss, color, method of initial
application, and its location (especially where critical lighting is
involved).
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