Had a call from a carpet retailer friend of mine last week. He was lifting some old carpet tiles, applying a self-levelling compound and then laying a commercial cord carpet in a school corridor. During fitting some adhesive got onto the carpet, as is his usual practice, he got a offcut wet it and rubbed the adhesive to remove it from the carpet. However this resulted in lots of foam rising out of the carpet and after drying left a dark patch on the carpet, no water ring though, just a dark patch.
He asked me to have a look and sure enough testing in other areas of the carpet gave the same result, even the area where the orignal incident took place was still producing a foam.
Neither of us have come across this situation before any thoughts, suggestions etc as to cause and any consequent corrective actions which should be taken most welcome.