Grey sandstone black marks ?

[Samsy]

Last week we finished laying our sawn and honed kandla grey sandstone.

We used full bed of mortar and used Silk fast joint compound.

I have noticed the following black marks which look like pencil have appeared on a majority of the 60 stones. I have tried to wash off, with no joy. Any ideas welcome...

https://ibb.co/m6qHCps
https://ibb.co/18JBrrB

Update now it looks like salt? Efflorescience ?


Link to photo here

[Tony McC]

Before I opened the links, I thought this was going to be yet another Sika FastFix Fur Cup (easily the single most comolained about product this year, knocking multi-decade winner, GeoFux, off its overly-familiar perch!), so it came as something of a pleasant surprise to find it's nowt to do with that benighted jollop!

All I can see in your photies are trace fossile....tiny flecks and traces of old wood that is milions of years old, trapped inside the sandstone since is was laid down in an old river bed or lake margin. It looks a little like charcoal (because it shares the same origin) and will range from minor specks and flakes to small twigs and the like. As the stone weathers, it's quite likely these will weather out too, as they are (usually) much softer than the stone matrix in which they lie.

Nothing you can really do about them. They are a natural featuire of the stone, so treasure them for what they are - a remnant of life from hundreds of millions of years ago, and there they are, in *your* garden!

[Samsy]

Thanks Tony, the final link is my main concern, any thoughts pls?

[Tony McC]

Frayed knot - it is what it is and you have to learn to live with them.

[lutonlagerlout]

the last photo is efflorescence
usually due to a high cement content in the bedding and sawn stone seems much more susceptible to it
it will weather out over time
LLL

[Samsy]

Thanks, since the time of writing the salt/minerals have started to rise to the top & wash away.

I am amazed how porous the stone is, the builder laid it during a week of torrential rain which has not helped - still has faint footprint marks which i hope will weather out like you say.

[Samsy]

It's been around 7 months since our Kandla Grey Sawn and honed sandstone was laid. Unfortunately it appears the staining is just not going away.... see image link. Thought's welcome

https://ibb.co/TPH2XLf

[catseyes]

Hi, just joined as my patio looks rather like yours but worse! I was told salt from the cement but on further research I think ours is down to reflective staining from improper laying... stupidly trusted a landscaper who has been in the business for 40 years and who's' work I have seen! Just my luck.

If you find anything that helps it to not look as bad, please post on here. I'm at a loss as what to do with ours.