GELCOAT COLOR-MATCHING February 17, 2018 18:12
COLOR MATCHING DETAILS
As a guide to color mixing, you could use a sheet of paint chips from a hardware store for the nearest color to that of the area to be repaired. Then ask the store assistant to give you the tinting formula (if they will!). You can also buy a color wheel from an art shop. These range from about $5 for a simple one to as much as $20 with a detailed book and charts on color theory made by Grumbacher (www.Grumbacher.com).
In synopsis, there are three primary colors: red, blue and yellow and these can be used to make secondary colors: e.g. green=(blue + yellow) ; orange=(red + yellow); purple = (red + blue) etc.
These secondary colors can then be mixed with each other and/or white or black to make tertiary colors. White and black pigments are used to control SHADE (darker, add black; lighter, add white). Obvious examples are brown=(orange + black), maroon= (red + black.)
Obviously white and black can also be used as stand-alone colors. An “arctic” or “snow” white is white with a slight tint of blue. Off white or cream colors are white with a tint of yellow, orange or brown. Grey=(black + white). For “slate grey”) add a tint of blue.
You can buy ready-made darkened or mixed colors (brown, for instance). However, be aware that as the gelcoat is diluted , its apparent color may change since the relative contributions of the primary components may change (e.g. diluted brown may become pinkish because red is a stronger or more “intense” color. The actual color of the gelcoat remains unchanged.
For some popular boats, you can buy gelcoat premixed to the original factory color, but this may no longer be as original due to fading of the original pigments or even changes in materials used to make the gelcoat since an old boat was manufactured. Never-the-less, a factory colors can be a useful starting point that is easily modified by small additions of other colored pigments. You may look at www.tapplastixs.com) for examples of the color pigments and dyes that they sell.
How to do the actual color matching
Color matching is best done in daylight, preferably not in direct sunlight. An area of gelcoat adjacent to that being repaired is dewaxed, lightly wet-sanded (600 grit), compounded and wiped with acetone or lacquer thinner to expose fresh, clean gelcoat.
Mix a reasonable amount of non-catalyzed gelcoat (enough for a total repair, (plus some spare, for future use). It is made up to the approximate shade of the color to be matched. It should be a little lighter for light-colored hull gelcoat and a little darker for dark-colored hull gelcoat. As an initial guide on solid colors, no more that 6-8% pigment is added. For a Cream color, for instance, make up (or buy) white gelcoat,
If color-matched gelcoat paste is being custom prepared for use, add Cab-O-Sil®, after color matching. This is not possible with small “Beginner Kits” available at West Marine. No catalyst is added at this stage.
Step 2: (example with light-colored Gelcoat:
Dab a little of the (non-catalyzed) gelcoat on the area of the boat to be color-matched, using a cleaned (with acetone) thick rubber glove-protected finger. The dabbed-on color should be too light. Then dab on a tiny spot of color pigment smearing it is such a way that a gradation in darkness of color intensity is produced. If you guessed correctly, at least one section of this gradation will approximate the underlying gelcoat color.
Transfer what you learned to the larger batch of gelcoat in the pot, adding new pigment, tiny bit at a time with plenty of stirring.
Repeat this process with the next tint that seems to be needed until the color is matched as close as possible. Then catalyst can b added and the repair done as described in Part 2.
AS A GENERAL RULE OT THUMB – ERR ON THE SIDE OF “LIGHTER”: ON LIGHT COLORS AND PASTELS, “DARKER” ON DARK COLORS. THE HUMAN EYE SEEMS TO NOTICE THIS LESS THAN THE OTHER WAY AROUND.
P.S. MATERIALS IUSED IN THE ABOVE GELCOAT REPAIRS ARE AVALABLE AT FIBERGLASS HAWAII (OAHU, MAUI, HAWAII AND SANTA CRUZ, CA, SANTA BARBARA CA) AND TAP PLASTICS (N. CA ).
NOTE: Use ISLAND GIRL Pink Cleansing Lotion™ for clean-up of non-catalyzed or incompletely cured gelcoat or other resins. It will not damage underlying good gelcoat as with acetone.