White Paint is New Weapon in War on Barnacles

Popular Science, marraskuu 1933

Barnacles, those under-water stowaways that cost American shipping more than $100,000,000 every year, are now in the scientific spotlight. Through novel tests and intensive under-sea searches, experts hope to banish this costly pest.

For more than three years, Dr. J. Paul Visscher, of Western Reserve University, has been studying the barnacle in its natural habitat. Trips under tropical seas were made, the hulls of hundreds of ships inspected, and thousands of ship-fouling specimens collected. During his studies he has found and identified more than twenty-five types of barnacles. Some are smaller than a pinhead, others larger than a pigeon egg.

Dr. Visscher's battle agains the barnacle marks the resumption of an age-old fight. For centuries these hard-shelled creatures have fastened themselves to ships' hulls and ridden free, stealing power and consuming speed. in tests, a barnacle-infested hull often wasted as much as one-third of a ship's fuel supply.

Mariners the world over have tried again and again to combat these acorn-shaped relatives of the lobster. The ancient Romans sheathed their ships in lead and copper and sixteenth-century sailors devised queer coatings of hair and pitch. But barnacles continued to accumulate. Even the poison film of modern antifouling paint fails to control them and keep hull free of them.

On small ships, barnacle growth often weighs hundreds of pounds. Occasionally, a vessel is found whose exterior cargo weighs more than three hundred tons. To remove this outer skin, the ship must be drydocked, scraped by hand, and finally repainted. in the case of giant ships such as the Leviathan, this procedure, a semi-annual occurrence, costs its owners more than $50.000.

During one of his adventurous trips below the sea, Dr. Visscher noticed a peculiar fact. Dark objects in shaded, under-water dells invariably harboned larger barnacle growths than rocks and surfaces of a lighter color. Barnacles, it seemed, shunned the light.

The investigator placed sample specimens of tile and wood along the ocean bed near his seaside laboratory. Some were painted white, a few red, and others black. after seven days, the test panels were removed and the barnacles that had formed were grouped, identified, and counted. in each case, the growth fastened to the dark-hued objects greatly out-numbered those on the lighter surfaces. The red panel contained more barnacles than the white, and the black as many as the red thus indicating a color preference.

Later, Dr. Visscher experimented with poison plants. Panels of wood and tile coated with antifouling films were placed in sea water under the same conditions. in thirty days, the test panels were almost entirely coated with barnacle shells. Only through the use of light-colored surfaces was the accumulation of barnacles effectively controlled.

Laboratory tests produced similar results. The eyes of the young barnacle, it was found, although sensitive to the blue-green light of the spectrum are not affected by the ultra-violet portion. in the blue-green glow under the surface of the sea, young barnacles shun the light and prefer the dark objects.

Thus science has laid plans for an attack on barnacles. Now chemists and paint experts are striving to develop light-colored paints that will stand up in salt water and soda, white-hulled ships may rob the barnacle of its costly sting.