I was tracking vocals the other night using a Rode NT1000 into a
Joemeek 3Q & noticed (along with others) that the Mic was becoming
sibilant - much more so than when we started. I tried repositioning
the singer/mic but to no avail. It did subside a bit after a while but
left me puzzled.

Does anybody know why this would happen? Is it a moisture issue or
something else?

Thanks
Greg