If You Could Live In Another Decade,...
ChatterBank0 min ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.This is an old builders remedy to a perennial problem. I have used it satisfactorily to remove large soot deposits on walls that have then been painted over with out any seepage.The theory behind this is that soot is carbon therefore at the opposite end of the ph spectrum to white vinegar which is an acid.I would experiment with a weak solution say 30 percent white vinegar 70 percent water, in a spray bottle, to start with. Work slowly from the bottom up wiping as quickly as possible, so you do not get great big run marks on the stone - remember this is an acid, so try a test patch first. You can always make the solution stronger if necessary to get the desired result.If its a small are use cheappo tooth brushes or if a bigger area a nail brush ( less 'flicky' than a traditional scrubbing brush!) I use a wee 'e-cloth' bottle (john lewis , waitrose) as it is light and more reliable than 99p garden sprayers which clog very easily and drive you round the bend!