When we were in Bangor (Ireland) last year a lot of the boats around us had a deep golden yellow which we really liked. Unfortunately we could not get any of the product call Semco from the local chandlers so we bought some teak oil which worked........for a while then it turned black. Definitely not the look we were looking for.
So we asked on the YBW forum and we given OnWard trading as a uk supplier. Turns out to be a three part process. The first part involves scrubbing an agent in inch by inch. This is really hard work (as you would imagine) but the dirt and crap that comes out was unbelievable. The second part is to a lot easier (phew) and neutralises the active elements of the first part. The teak now looked like new.
Final part is to put on the sealant, at least two coats. The first coat you put on as much as the teak will absorb. You have to be careful to ensure an even colour (we had chosen golden honey). One of the most prominent feature on the Oceanis is the coach roof grab rail, which came up especially good. Needs another coat (no need for part 1 or 2) every four to six months depending on climate – six months here, four months in the med.