Pure Chem Oxalic Acid Cleaner 5% Solution, Oxalic Acid Wood Bleach 1L

Works great for me

Very good the acid removed all the ungrounded stains off the white of my yacht, Definitely be ordering more at the end of the season

It does work, just need to apply several times for some worse areas, got enough to last a while

It does what it needed for.

Very effective at removing black marks caused by tins left on worktop. I used a cotton bud dipped in the solution to trace the outline of the stain. I needed to repeat every half hour or so , after about 3 or 4 rounds all was good. Some soaked in water marks took more . I wished I'd taken before and after shots but I'm a very pleased customer.

No miracles

Waste of money. Do not buy.

This is oxalic acid, it's pretty straightforward. If you need instructions then you shouldn't be buying this product, let alone using it. That's a bit like needing instructions on how to use vinegar! And this works, you just need to know how to use it. I had the most horrendous rust stain on my boat's roof, where the previous owner had left a metal tray lying on it for two years. The stain was deep and measured a good half metre in length, with further rust smears running off it. I spent a few hours with a scrubbing brush and about a quarter of this bottle over a number of sessions. Unfortunately I don't have before and after pictures but take my word that it was a massive improvement after treating it with this. I recommend using washing up liquid, especially if you're rubbing on a vertical, as it holds the acid in place. Depending on the surface you can leave to soak for 10 minutes, but I find it's better to apply it a number of times after leaving for only 30 seconds each time. My only complaint is the expense. It's cheaper to buy crystals and make your own solution, but this stuff works as expected.