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?
There's a risk of staining no matter which mortar you use, with or without dye...personally I wouldn't reccomend dye, because within 6 months it will have gone away to leave natural mortar...it lasts slightly longer on walls etc but on paving slabs it simply washes off, or goes green.
I've been using cement dye in lime mortar to point up around prefinished windows (windows dark stain on meranti, lime mortar with yellow dye to match local sandstone colour). Yes, I've succesfully used masking tape on the frames to minimise staining. For the small amount of paving/tiling I've done (fire hearths), I've just used care - and yes there is a little bit of staining - but it looks right on irregular reclaimed building materials.
...personally I wouldn't reccomend dye, because within 6 months it will
That hasn't been my experience of using Febtone Yellow in lime mortar to repoint around windows - 1.5 winters later and it still looks just as it should.
Admittedly none of mine is outside on horizonal surfaces.
Agree with you though, some degree of staining - with or without dye - is pretty unavoidable.
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.
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
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(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!
Oh go on then, I'm about to lay some black limestone for a hearth. I was going to just mix some ash in to a standard mortar mix. I'll try it first. Bung it on tinypic.com or wherever.
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?)
as lime mortar but some or all of the sand is replaced with ash. It was forbidden on many building projects as it was more prone to failure than lime mortar. In many cases it was used anyway on the non visible areas, as coal ash was something one had to pay to get rid of.
If repointing patches of black mortar, the logical thing would be to use more black mortar.
Sorry for the delay - been waiting for it to stop raining so I can take some 'real' pictures - these slabs change colour significantly when wet (get much darker), and indeed the mortar joints also do except they seem to take longer to dry out. Anyway, gave up waiting for it to dry out however the following should give some idea what it's like:
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smaller slabs seem to take the longest to dry out and so whilst they, and a number of the other ones, may look like they've been stained (particularly at the edges) they're actually not.
Have still got a bit more to do, including rebuilding the steps (to cover the full width of the french doors) along with some gravel infill between the patio and decking (this provides drainage to a nearby drain) but as far as I'm concerned the hardest bits are done!
You've done a good job of it...I always find it hard avoiding making a pattern when using random shapes like this, I end up repeating the same pattern without realising it.
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