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Posted: Fri Aug 19, 2011 9:39 am
by Rake
Hi all.
I have just finished laying our hard in Indian sandstone and most of it has White powdery residue when dry.
This is undoubtedly from the wet mix which went all over it dilute with water. We have washed it and brushed but when dry comes back.
Will it eventually go or can it be cleaned off ?
We have not yet pointed.
Cheers
Rake
Posted: Fri Aug 19, 2011 12:56 pm
by Tony McC
Grrrrrr! 
Posted: Fri Aug 19, 2011 2:25 pm
by lutonlagerlout
try hydrochloric acid on an off cut,if that works you may use it at your own risk on the flags
dont forget PPE
LLL
Posted: Fri Aug 19, 2011 4:28 pm
by DNgroundworks
Oh dear, i think you will struggle to remove it, cement based slurry jointing is not for DIY'ers. Very labour intensive in the cleaning stages - even though i am no expert!
Posted: Fri Aug 19, 2011 5:07 pm
by RAPressureWashing
Be very careful with the hydrochloric acid, as you can damage the stone and not reverse the damage. Can you post a photo of the problem?
Posted: Fri Aug 19, 2011 8:07 pm
by Rake
Thanks all. Will upload pics tomorrow as dark now.
It's not jointing as no pointing done yet. It's cement residue all over the flags.
Wet it looks fine dry it has White powder.
I can get a pressure washer if you think it might work ?
Posted: Fri Aug 19, 2011 8:20 pm
by RAPressureWashing
Rake,
Pressure washing alone may not do this, and there is always a chance that you may etch the surface, once you get a chance to post a photo, I should be able to point you in the right direction on how to remove this safely.
Posted: Fri Aug 19, 2011 8:38 pm
by Rake
Thanks r&a it's very much appreciated..pics tomorrow am.
Hagesan Natural Stone Cement And Lime Remover (1 Litre)
Is this snake oil ?
Posted: Fri Aug 19, 2011 9:38 pm
by Rake
Its the white lime haze that I'm on about.
I brushed up with a heavy yard brush and some of the patterns are now visible but its not all gone.
pressure washer in the boot now but will wait your advise before acting.
Cheers.
Rake.
Posted: Fri Aug 19, 2011 10:26 pm
by lutonlagerlout
its just a fine cement residue
use acid on an off cut if it works on that your stone will be ok
LLL
Posted: Sat Aug 20, 2011 8:16 am
by RAPressureWashing
Rake,
Cheers for the photos, a very light acid wash should cure this either Lithofin's cement away or builders clean, these are a blend of acids and not as agresive as hydrochloric acid on it's own. Try a test on an out the way area or cut off piece of stone first. As with all acids there is a slight risk of colour change on sandstone so please do a test first.
Read up on what PPE is needed. You really don't need the pressure washer for this other using the extra flow of water to rinse/flush of the chemical. Give me a shout if you need anymore help.
Posted: Sat Aug 20, 2011 10:09 am
by Rake
Thank you so much. Will report back when done.
Posted: Sat Aug 20, 2011 12:39 pm
by Rake
Last q. Do it before or after mortar pointing ?
Posted: Sat Aug 20, 2011 1:15 pm
by RAPressureWashing
Personally I would do it before pointing, but you will have to make sure you don't repeat the marking with the pointing or you will have to do it again. If you go for after pointing, a rule of thumb we use with pressure washing is no cleaning agents or pressure washing for at least 6 weeks after pointing so to give the pointing time to properly cure.
Posted: Sat Aug 20, 2011 7:37 pm
by Rake
Thanks yet again. I thought it was a silly question but evidently not !
Before pointing it is.
I have a roughneck mortar gun to keep things clean.
