If you are referring to solder mask (green film), it is sold in pens by various vendors.
--- In Homebrew_PCBs@yahoogroups.com, "jberghout" <jberghout@...> wrote:
>
> Hi. I'm new to the group. I was recently bitten by homebrew PCB bug. But I've been scratching my head, wondering why it so hard to find the solder resist film in the US. I realize that a solder resist is no necessarily necessary for DIY boards that don't use surface mount components. But it's something that I would still like to use to make my boards look more professionally, and to protect it from the environment.
>
> The ink they sell from china on ebay is primarily used for silk screening. and I might end up going this route, but it sure would be nice to have film available for one off designs.
>
> Is there just not enough demand? Are there any other reasons?
>
> Thanks in advance...
>