Hi John,
You will see from my previous comments on this topic that I am an advocate of Boracol. After many years of cleaning my decks with various prorietory brands, including oxalic acid based ones, I now simply clean my teak with soap and water and then paint on one coat of Boracol by brush at the start of each season. It takes about 10 days to work but then the biocide takes effect removing the black bits and the green bits leaving the teak a beautiful silver grey. Importantly there is no scrubbing involved. Mindful of Irish weather, Daria Blackwell was amused when I mentioned that ideally 3 dry days were necessary after applying boracol. You will see that other members have suggested cheap ways of buying boracol. Hope this helps...
Tony

Well, I did eventually succumb and had SEMCO applied professionally in Jolly Harbour at the beginning of April. Serendipity looked BEAUTIFUL on completion!

Now, she is not a wet boat by any means and the weather was kind to us being largely behind the beam, so we didnt take oceans of water over the deck along the way home. However, by the time we arrived in Falmouth after about 10 weeks perambulation up via BVIs, Bahamas etc. and across the Atlantic, there was little or no trace of Semco anywhere outside the cockpit.

I conclude that it might look OK in a marina or on garden furniture, but is pretty U/S at sea.

An[other] expensive lesson....

I 've been using up all the Teak cleaner/brightener I had and still had a vast surface area of deck to tackle. It 's been so wet this year, the mold and mildew is terrible. Our local chandlery carries minute bottles of teak cleaner at rather high prices. So I went looking online. I learned on a Forum that in Ireland one can order chemicals of all kinds through the chemist (pharmacy). My pharmacy ordered a 1 kg container of oxalic acid for which I paid 65€. I do believe it will last the remainder of my boating lifetime.

I have found the following recommendations useful:
[ul][li]dampen the deck area with salt water
[li]dissolve 3/4 lb crystals to a gallon of HOT water (or 3 oz to a quart). A quart is supposed to be enough for a 50-60 foot boat depending on how dirty it is.
[li]paint the oxalic acid on with a paintbrush[/li]
[li]wait a few minutes then scrub with a stiff bristled brush
[li]rinse with a dilute vinegar solution to neutralize the oxalic acid
[li]rinse with plenty of salt water or fresh water if you have access
[/ul]

Plain bleach is suppose to be the "brightener" in a two-part cleaner.

The first time I tried to start working on a nice sunny day, the deck kept drying out before I could scrub (the sun is very intense here when it does come out). So working on a cloudy day worked much better. The rain that followed afterwards gave it a nice fresh water rinse.

BTW, they say never to let the oxalic acid dry out on the deck. It crystalizes into razor sharp crystals that remain imbedded in the deck. Rinse, rinse, rinse.

I do like the idea of Boracol, Tony. I 'm going to ask our chemist if she can get that for me, too. There is a useful thread on Boracol on YBW.

Vice Commodore, OCC