Hi, this is Halsberg rassy factorys offical tips over 20 yars old. Boracol!
boric acid kill black mold, is gentle does not consume the wood, such as teak, many commercial cleaning. The product name is boracol!
https://www.acslimited.co.uk/teak-deck-maintenance-boracol/
In the long run the best way to treat the teak deck against
mildew is to use Boracol. Boracol is a liquid that is uncoloured and thin like water. It is sold in normal
chemist shops and hardware dealers. It is marketed as a treatment against mildew for garden furniture.
Use a normal paintbrush and paint the deck with Boracol. Never use a normal brush on the teak! Do
the work on a dry dray. If it rains too much Boracol will be washed away. It does not matter if it is
drizzling the next day but if it rains the complete day or over splashing waves washes over the deck, the
Boracol will make no effect. That would flush the Boracol way too early. If it does not rain, spray the
deck a little with water. This little amount of water only helps the Boracol to penetrate into the teak.
After three to seven days you wash the deck with a sponge and cleaner, for example green soap. Please
do not be afraid if you do not see any positive result immediately. On the contrary, the deck looks
worse than it did before the treatment. After about ten days things will start to happen. The mildew has
disappeared and the deck is clean. The mildew will not recur for some time. Do not be afraid to repeat
the treatment now and then."