On 26 July, 21:41, "Harry Stottle" wrote:

An old plasterer told once me the best way to neutralise soot, and get it to
accept plaster, is to mix cow dung with water in a bucket and paint it on.
Just searched to see if this was true, and found the following link:-http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionI...

I'd ask Anna Kettle about this, but I'm fairly reliably informed that
any old recipe for cow dung related plasterwork needs care if you use
modern dairy output. It's the change in diet and hyper-breeding of
cows that resemble industrial fermenters. If you're "shopping" for
cowpats, take them from the fields where the bullocks are, not the
milking parlour or the slurry lagoon. If you do use dairy output,
check that the water content is still what the recipe expected.

Errors in this area may leave you with a bathtub full of extra-runny
wattle & daub mix that refuses to stay daubed and gets stinkier by the
day...