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I recently did a verandah soft wash. Where the painted wooden ceiling meets the sandstone blocks, there has been some tannin run.

Basically there's a very small gap where the ceiling meets the sandstone wall. This is undercover. I washed the ceiling part and some water go up the crack and a large amount of tannin ran down and stained the sandstone.

It also ran through the cracks in the painted ceiling where there's cracked paint. The result is pretty terrible.

I intend on going back and applying the following options. Please let me know your thoughts and experience.

1. Start by wetting and applying oxalic acid and a little dawn with a paint brush. Leave it 30mins, maybe scrub and rinse.

2. If it doesn't fix it, try applying S percarbonate in same fashion.

3. As a back up I read Phosphoric acid might work like oxalic acid.

As for the paint drip stains, what's the best solution for that? Percarbonate? Bleach? or just paint it?

Thanks everyone.

Brian