51 wrote:
Hi all.
The back yard paving is not far from completion.
I chose indian stone and I'd like to dye the mortar between the slabs
to a more attractive colour (probably brown).
The pavior told me that there is a risk of staining.
Is this correct?

If so, how to minimize the risk? (masking tape?)

Arthur

Hi Arthur,

I've just done the very same job - 'welsh slate' cast slabs from
Bowland Stone with matching dye for the mortar.

I too was aware of the potential for staining and so I followed the
comprehensive 'coloured mortar' case study at
http://www.pavingexpert.com/point04.htm (great site in general, if a
little *too* much information!).

The key to minimising staining is minimising water - you need enough to
hydrate the cement but too much to cause staining to the surrounding
slabs. Indeed, choosing the right day was the most difficult for me -
I've been taking an unnatural interest in the weather and the so-called
forecasts for a couple of weeks now and finally struck lucky on
Wednesday when the seemingly-endless rain finally stopped.

As the case study suggests (which aligned with the instructions on my
dye which was reassuring) the absolute minimum amount of water is
needed... the water in the sand is pretty much sufficient alone.

My dye was mixed 1 part to 20 parts cement. Whilst the dye was jet
black the abundance of cement soon made it all disappear and I was left
with a very-much-cement colour to this 'coloured cement'. However, when
the coloured cement was mixed 1 part to 4 parts building sand the
colour *really* came out and the mixture was very dark very quickly...
it must've been down to the water already in the sand. In perhaps half
a bucket of mortar I added a splash of water (literally that little)
which had some plasticiser in it however the mixture itself was
aggregating quite well and could be smoothed to a relatively smooth
finish.

As the case study mentions, if the slabs are dry then any spillover
whilst working should not stain - I can confirm they didn't too (which
was a relief). Indeed, the loose (non-compacted) mortar on the
surrounding areas soon dried out thus not staining the slabs. I could
see that the slabs were soaking moisture from the mortar and was
worried they'd be sucking in dye too however 24 hours on I can confirm
that they didn't.

All-in-all I've extremely pleased with the final result - I must say it
was the pointing that I was dreading the most given the 'stain' factor
but in reality it wasn't a problem given the steps I followed.

I've got a few photos which show some of the steps in general if
they're of any interest... indeed given the pointing took me 7 hours I
want as many people to see the final result as possible!

Mathew