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Andrew Gabriel

In article om,
writes:
Stuart Noble wrote:

A lot depends how sloppy the mortar is. Mortar dyes are dispersions of
oxide particles so they shouldn't wash out, any more than the sand does.

well, i can assure you that it does. And whats worse, it washes out
streakily. Thats with black dye. Red, which is iron oxide, might be
different

Well, the front of my house is lime mortar with a black die.
It's nearly 100 years old and the die hasn't washed out.
When I've needed to repoint a few bits, I have been unable to
make my mortar dark enough, even by chucking in much more black
die than you're supposed to -- it still looks grey in comparison.
I do wonder what they used 100 years ago? (Soot maybe?)

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Andrew Gabriel