Dry dry steam at 60 to 90 psi or end a heat gun see if the is a change.

Even doc fred granite  test kit for dying. 

Has to be natural  dye mold or man made stain. Have scratch  the top to see if it in the stone?

Hector 

Sent from my Verizon Wireless 4G LTE smartphone

-------- Original message --------
From: Stephen Webb <stephen@newlifemarblerestoration.com>
Date:03/30/2015 11:38 PM (GMT-08:00)
To: sccpartners@stoneandtilepros.simplelists.com
Subject: Re: Trying to figure out what this is

Yes I used D/2 biological which has worked great on other mold projects but no effect here.

On 3/30/2015 5:27 PM, Hector Castillo wrote:

Don't  they make  a spray  for that type of mold.   dd2. I think not sure

Hector 

Sent from my Verizon Wireless 4G LTE smartphone

-------- Original message --------
From: stuart rosen <mail@stoneshine.com>
Date:03/30/2015 7:58 PM (GMT-08:00)
To: sccpartners@stoneandtilepros.simplelists.com
Subject: Re: Trying to figure out what this is

I would guess it has to do with moisture-spent some years climbing on sandstone out west.

Moisture caused some types of discoloring but if I remember most discolorations were black and similar to what's on your stone.

Maybe it is lichen growth-interior or exterior?

Maybe you need a mildecide , fungicide, biocide product. 

 

On Mon, Mar 30, 2015 at 9:46 PM, <hectorcastillo@comcast.net> wrote:

is the black in the grout ?

Hector Castillo

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