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Old 07-12-19, 09:31 PM   #2
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
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First floor or second. If the floor is susceptible to outside water, then it may be mud.

I am thinking very old adhesive.

Do you have access to a microscope. A low power (10-20 x) will reveal mold if it is that.

Mix some with water. Does it stink?

Steve
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