What I did, was printed the layout on polyester paper and put a little bit of water between the board and the paper and exposed a sensitized board.
The water's surface tension holds the mask (polyester paper) tight against the board. Glass is usually used in this step, but water works fine. We are only talking a few drops or so.
--- On Sun, 3/22/09, DJ Delorie <dj@...> wrote:
> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box
> To: Homebrew_PCBs@yahoogroups.com
> Date: Sunday, March 22, 2009, 4:36 PM
> KeepIt SimpleStupid <keepitsimplestupid@...>
> writes:
> > Just try some water between the film and the board.
> I've found it
> > works fine.
>
> Except I want to image a circuit board, not a large grey
> blob. The
> ink on my films will run if they get wet.
>
> (I assume you really meant "photoresist film" -
> I've got the laminator
> for that. I'm talking about the photo master for the
> exposure box)