This is usually wanted in brown or copper color and the most effective paint known for the purpose contains 5 pounds copper oxide in the form of fine scales, although it has been made with what was known as cement copper, which however contains as much as 25% other mineral, such as silica, clay, iron oxide, etc.
The following formula produces a very high type of such a paint, preventing the adhesion of barnacles and formation of marine growth.
lbs. Mineral Brown or dark native red oxide;
lbs. copper scales in fine division;
lbs. refined pine tar;
lbs. shellac japan;
lbs. heavy petroleum spirit;
100 lbs. or 9 gallons of paint.
Note. Linseed or other vegetable oils must be avoided as forming part of this type of paint, excepting the very small portion contained in the shellac japan, because the presence of appreciable percentages of vegetable oil will promote marine growth.
Copper Paint, so-called, for Yacht Bottoms.
Brown color is very seldom desired here, the favorite colors being green and bright red. The insecticide here need not necessarily be copper, but can be mercuric chloride (corrosive sublimate) or mercuric oxide (red oxide of mercury), either of which, of course, is much more expensive, than the oxide of copper, but being more active, less can be used in proportion, and the selling price of yacht compositions being higher, the maker can afford their use.