Black tar like substance

[boazcan]

New one on me.

We do sealing of grout on new houses. We did over 1400 sq ft in this house yesterday and 3 places there was a black tar like substance that oozed out of some grout.

I'm assuming our solvent based sealer penetrated a small opening where the grout should meet the tile. As it dried it brought it up.

What the heck is it? Some sort of float membrane. We have settling issues here so it may help in cracked tile and grout. Black thin set? Never seen it before and we do a bunch of new grout seals. But not in this new neighborhood yet.

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[dealtimeman]

Never seen that before. Keep us poser in what works to remove or the actual source.

 

[Desk Jockey]

I was thinking the mastic.

 

[Bee Busy]

I've used a diamond tipped grout getter with some colorseal for that before