Gemini 105Mc Owner’s Manual
60
Copyright © 2004 Performance Cruising Inc.
FAQ Courtesy of BoatingMadeSimple.com
Fading
Antifouling paints are not meant to be cosmetic or decora-
tive coatings and while every effort is made to make them
as aesthetically pleasing as possible. The copper compound
within the antifouling is difficult to mask with color pig-
ments.
All antifouling paints change when they are immersed. So
don't be surprised when you have finished and the color is
not what you had hoped from the color chart, The true color
will establish itself after the boat has been launched. Co-
polymer and ablative type coatings tend to fade more than
hard antifouling paints.
Along the waterline you will often the antifouling looks dirty
or faded, and can even turn green. This is due to the reac-
tion of the paint with oxygen forming green copper oxide.
Also paints with a higher copper content will turn greener at
the waterline than paints with a lower copper content. For
these reasons you should try keep the paint as close to the
true waterline as possible. Fading is more noticeable in of
ablative coatings than in hard coatings.
How Often Should I Paint My Boat?
That depends on the type of antifouling that is used. The
longevity of multi-season copolymers such as Micron Extra &
Micron CSC is related to the amount of paint applied. These
paints will retain the antifouling properties as long as the
paint is on the hull. Hard antifouling paints work by leaching
biocide out of the paint film and leaving the paint film be-
hind. When this paint film is left out of the water it oxidizes
and any biocide that is left in the coating will not leach out
at the proper rate to control fouling.
Must I Sand the Bottom Before Repainting with the Same
Antifouling Especially Since It Was Powerwashed in the
Fall?
Antifouling paint is not meant to be exposed to the elements
and when it sits out of the water for a couple of months the
outside layer of paint film becomes oxidized, and gets soft,
plus it picks up dirt and dust. New paint does not adhere
well to this type of surface and may begin to peel off. Most
non-copolymer paints have a porous "leach layer" and if they
are painted over, after just a power washing the pigment
and the resin penetrate into that porosity and leave a
"blush" of cuprous oxide on the surface. This is a cosmetic
problem and does not really affect the antifouling quality of
the paint but most people if they buy blue paint they want it
to look blue not purple. High-pressure fresh water washing
(3000 psi) will remove the leach layer but the paint will
need to be over-coated immediately after it dries. The other
reason for sanding antifouling paint is that there is only so
much paint that will hold onto a given surface. That amount
may be 10 coats or the first coat may delaminate. This is the
related to how good the original surface preparation was
and how it is maintained between recoating. Sanding when
recoating will add to the longevity of the bottom jobs. By
sanding the bottom in the spring you will get more coats to
adhere and forestall the day when you must remove all the
antifouling paint from the surface. Soft rosin based antifoul-
ings must always be sanded even if they have just been pow-
erwashed.
Keep in mind that the hulls require only a light hand-
sanding and not a power sanding.
What Is The Difference Between Hard & Soft Paints?
Antifouling type is dictated by the quality, combination,
quantity and type of resin.
Copolymer and Ablative Antifoulings
These types of antifoulings are partially soluble which means
that as water passes across the surface of the coating, the
coating wears down much like a bar of soap would wear
away The action of the water steadily reduces the thickness
of the paint at a controlled rate, which results in always
having fresh biocide at the surface of the paint throughout
the season. For this reason these types of antifoulings have
the capability to perform in the areas of highest fouling
challenge.
Hard antifoulings leach the biocide out of the paint film and
leave the paint film behind on the hull, which causes a build
up of old, spent coatings, Because copolymer and ablative
types of antifoulings wear away with use. There is no build-
up of coatings that will eventually have to be removed from
the surface. The minimal build up reduces the maintenance
and preparation needed when it is time to apply more anti-
fouling. In addition Copolymer types such as Micron Extra
with Biolux and Micron CSC can be hauled and relaunched
without repainting as the longevity these coatings are re-
lated to the thickness of the paint.
Ablative types such as Fiberglass Bottomkote Act do not
retain their antifouling ability for more than 30 days after
being hauled out.
Hard Antifoulings
The technical term for these types of antifouling paints is
"contact leaching". The paint dries to a porous film that is
packed with Biocides, which leach out on contact with water
to prevent fouling growth. This leaching is chemically design
to release biocide throughout the season, but the amount
will steadily decrease until there is not enough biocide com-
ing out of the paint film to maintain fouling protection.
Once the biocide is exhausted, the hard paint film remains
on the boat. One of the main benefits of this type of anti-
fouling is its resistance to abrasion and rubbing. This makes
it ideal for fast powerboats, racing sailboats or boats where
the owners have the bottoms cleaned regularly.
Most hard antifouling paints can be wet sanded and bur-
nished prior launch to reduce drag and improve hull speed.
A disadvantage to hard antifouling paint is the buildup of
residual paint film that occurs when the surface is not prop-
Bottom Paint FAQ
