I have been the owner of a teak decked sailing yacht for 12 years and have spent considerable time cleaning and treating the decks. Only in the past 2 years have I really discovered the wonderful qualities of Boracol. Halberg Rassy owners are probably well aware of the marvellous qualities of Boracol because that company promotes its use, but others may not be so familiar with the `secrets ' of this product.
I use Boracol 10RH, which is primarily a biocide for the control of lichen, fungal and algal growth on stonework and masonry. More recently, however, Boracol has been used as a treatment against mildew and spotting on teak decks. The recommendations from suppliers are:
* Make sure teak decks are free from surface water/ dry before application.
* Apply by brush or roller.
* Allow 3 days to `dry`.
*For best results the deck should not come into contact with rain during the `drying ' period.
After about 10 days things will start to happen, the mildew will disappear and will not return for some time (I apply annually) and the teaks will attain a beautiful pale silver tone.

My apologies if this treatment is well known and I am preaching to the converted. I had to learn the hard way!