Indonesians make coral anti-fouling coating
As an interesting footnote to Pete Taylor's excellent article on barnacles ("Mariner's nemesis," Issue No. 85), I would like to tell you about an ingenious and "green" method of anti-fouling developed by the Bajao and Bugis peoples of Sulawesi, Indonesia, that I observed while sailing on my Bajao-built turtle-hunting sloop during the early '70s.
While I did not engage in turtle hunting myself, turtles were the major source of cash for the Bajao and Bugis, hardy sea-gypsies (even their villages are built on tidal flats; they come to land only for fresh water and to trade) who would regularly sail their well-found wooden sloops as far as Australia in pursuit of turtles. Their method of dealing with marine fouling involved only two substances: coral and coconuts. Fortunately, these two ingredients are abundant in those remote islands.
First, the coral is burned to create lime. Then it is pulverized in a large hardwood mortar made from a hollowed log, some two feet wide by two and a half feet deep. Then six men gather around the mortar with pestles made from hardwood branches about three inches in diameter and five feet long. The six men pound the powder as coconut oil is very gradually added to the mix. What they are doing is making a coral putty. This is very difficult and involves relays of men to maintain the pounding for about 18 hours non-stop, slowly building up the right amount of heat in the putty for it to become smooth and pliable. It is a moment of great triumph when the ordeal of putty-making is finally done.
The process is carefully timed so that the ship to be plastered (most are around 45 feet in length, 13 feet in beam, and internally ballasted) is blocked up on her keel on the beach, held vertical by four crotched braces. The putty is taken immediately to the boat and trowelled in place. On a new hull, a layer one-inch thick is applied. The putty quickly hardens to a rock-like consistency. This layer serves two purposes: as a base for the final anti-fouling coating and as a shield against the entry of teredo worms, which, by the way, are a main reason why people used to cover wooden hulls with copper plates; marine borers don't merely slow a ship down, they sink it.
Next the workers take more of the burned powder coral (without coconut oil) and mix it with water. This is then brushed over the plastered hull where it dries to form a crusty layer of lime to which barnacles, etc., will adhere. After a month or two of accumulating fouling, the boat is returned to the beach where her hull is scrubbed with a half coconut shell. All the fouling easily flakes off, along with the crusty lime coating. To renew the coating, a fresh water-lime mixture is then applied.
It seems that "easy release" surface technology is not as new an idea as it might seem.