Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

The trick with TT is to find a temperature that is hot enough to make
the toner plastic and sticky, but not hot enough to make it liquid. If
it's too cool, it won't stick. If it's too hot, the toner spreads out
(smears). The "right" temp depends on the toner brand, too, with
Brother needing a hotter temperature than others. I've been using 340 F
for HP toner, but found that 370 F or so is needed for Brother toner.

As for direct-laser: one thought is to find a water-soluble coating you
can put on the board, so that you can laser print onto the coating but
have it wash away in the etchant. You only need enough to keep the
copper from discharging the static charge the laser printer uses.