Homebrew PCBs

hey there. I posted pictures on the files area. It's water based
emulsion, the MSDS states that it is a "vinyl dispersion", a fancy
name for white paper glue. It's purple in color,
bichromate-sensitivized. Bichromate is illegal in many countries.

I tried using diazo-sensitivized ink, color green, but it wont stick
to the copper as this one.

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
> hjf2k2 wrote:
> 
> > Hi all, It's me again. I've been busy for a couple of months now, but
> > I accidentally have perfected the cheap photo etching method I posted
> > a few months ago.
> >  [deleted]
> 
> Hi,
> What type of screen emulsion did you use. It sounds like its not water 
> based like the one I tried to use. I recently posted a reply to Bob 
> about my failure using the screen emulsion. I'm not up to date with 
> photocure screen emulsions, but I'd image not all are the same.
> 
> "Hi Bob, it was a long time ago, but from what I remember the emulsion
> was nothing special, just common silk screen emulsion. Color was red and
> smelled a bit like PVA glue. After coating, drying, exposing and
> developing, the emulsion became quite solid and difficult to remove.
> However it would "swell" slightly in etchant, and I think somehow a
> microscopic amount of etchant would reach to the copper surface, causing
> the bond to break and it lifts off. Unlike photoresists, these emulsions
> don't seem to be completely impermeable to aqueous solutions."