We recently resurrected our horribly weathered teak; the previous owner had let it go to the point where it was mostly black, partly gray, and everywhere ugly. After trying some lesser products with little success, we went straight for the bad actor, the Te-Ka two part system. This stuff is very caustic and extremely nasty, but it made our neglected teak look like new. Best of all, it required almost no scrubbing! A WORD OF CAUTION: The Part A will turn your white gelcoat a lovely shade of purple. At this point we were nearly apopleptic, until we disovered that the Part B, when applied directly to the gelcoat, "unlocks" the A and the purple stains come off immediately. In fact, we used the Part B to remove a number of stubborn stains on the deck. Who knew?