Here is another picture showing the problem:



On Thursday, October 22, 2015 8:41 PM, Roger Konarski (via sccpartners list) <nobody@simplelists.com> wrote:


This email was sent from yahoo.com which does not allow forwarding of emails via email lists. Therefore the sender's email address (qm144@yahoo.com) has been replaced with a dummy one.

I looked @ a job. White grout lines have a black residue on top. I can scratch away the black residue with a key. The question I have, why the black build up? See attached pitures.

Thanks,

Roger
 
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