So, to clarify, are you saying to spread the ink on the board, then cover with cellophane? Then while still wet, place the mask and expose?
--- In Homebrew_PCBs@yahoogroups.com, James Sleeman <bitsyboffin@...> wrote:
>
> Gustavo Villada wrote:
> >
> >
> > http://www.instructables.com/id/Professional-Home-Brew-PCB-Creating-a-solder-mask/?ALLSTEPS
> > the secret is the UV paint.
> >
>
> Make sure you read the comments on that instructables. The guy who
> wrote the instructions advocates drying the paint first, in short, he's
> doing it wrong.
>
> Also, cellophane bags are good for the plastic covering (at least true
> cellophane). Some plastics are no good as the ink bonds to them just as
> well as to the board.
>
> Spread ink thinly, too thick and it doesn't cure to the bottom.
>
> Exposure time is long (25-30 minutes), although a short exposure during
> your initial experimentinng will be strong enough to see how it went but
> easier to clean off and re-use your test piece.
>
> After cleaning off the pads, give the board another healthy dose of UV
> to really be sure that it's cooked to perfection.
>