"Pete C" wrote in message
...
Could be that silicone spray has been used nearby or contaminated
something, or it may even be anti-clog additives from sandpaper.

I neved used silicone spray. So I think it is the anti-clog additive. I did
clean though, with xylene-based thinner, but probably not good enough or the
used rag was already too dirty.

Meindert