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Stuart Noble

wrote:
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

NT

Got the hiccups today?
I think all cement dyes are oxides and there is a chemical reaction with
the cement that helps bind them. If they're added to the mortar rather
than the dry cement, I guess there's a chance that won't happen.
I'm looking at some I did round a drain cover a couple of years back.
Yellow and red. Looks bloody awful, but it hasn't washed out.