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UK General Cleaning Forum => General Cleaning Forum => Topic started by: ross12345 on April 09, 2009, 10:11:24 pm

Title: how do i remove the blck spots on the patio slabs
Post by: ross12345 on April 09, 2009, 10:11:24 pm

how do i remove the blck spots on the patio slabs please iv preshured washed em but cant remove the black spots

Title: Re: how do i remove the blck spots on the patio slabs
Post by: Griffus on April 10, 2009, 12:05:26 pm

There are occasions when certain marks become absorbed into the slabs thus becoming part of them.

No amount of pressure will remove these. You will damage the slab if you try.

I always point this out before starting work so the customer is not left disappointed.

Title: Re: how do i remove the blck spots on the patio slabs
Post by: drivewasher on April 11, 2009, 10:00:55 am

The black spots are lichean, a ytpe of fungus. Pressure washing does get the surface fungus off but it has a kind of root syrtem that grows into the fabric of the surface it's on, this is what you can still see. looks like black spit or oil marks.
There is a chemiacal available to kill it but it takes a few days, then it can be removed by pressure washing.

Title: Re: how do i remove the blck spots on the patio slabs
Post by: drive surgeon on April 12, 2009, 06:28:54 pm

lichen remover  :)

Title: Re: how do i remove the blck spots on the patio slabs
Post by: drivewasher on April 13, 2009, 11:19:26 pm

Go on then J show us!

Title: Re: how do i remove the blck spots on the patio slabs
Post by: Ged on April 15, 2009, 05:42:55 pm

wet the area then spray the spots with a little dilute hydrochloric acid (brick acid) , dwell for 10/15 minutes,this will soften the lichen just enough to shift it with a turbo lance. take sensible precautions when using the acid and wear protection, wash the area down with plenty of water and  be aware where the run off is going.

Ged

Title: Re: how do i remove the blck spots on the patio slabs
Post by: collins ReVive Stoneworks on April 15, 2009, 07:16:49 pm

well done ged

did that on my own slabs acid is great for most things

pressure washing alone seems to encourage growth after and very quickly

so does anyone have an after treatment???

Title: Re: how do i remove the blck spots on the patio slabs
Post by: BDCS on April 15, 2009, 08:48:00 pm

Lichenite