Homebrew PCBs

>Any suggestions or ideas for identifying the cause?
I used to work on copiers and we would see these kinds of defects all the 
time with
various papers. The copier manufactures would call it blow off. I am not 
sure of the
exact cause but I suspect a charge buildup on the paper and as it discharges 
against
"something" fusing rollers guides whatever it blows the toner around.

Some things we used to do to minimize it was change the charge voltages 
(which I dont
think you can do on a printer)and toner density you might be able to turn on 
a toner saver
or something to make it less dense.

Most of the time its just a paper incompatability with the printer that cant 
be compensaited
for.

I dont think that its to much moisture in the paper actually it may be to 
dry if you get to much
moisture you will get large patchy voided areas.

Good luck
Ken