Phil,
I have used this, a lot less £s than Mega!!
http://www.ebay.co.uk/itm/Photoresist-Dry-Film-A5-x-10-developer-DIY-PCB-Photo-Etched-PE-/250900965034?pt=Vintage_Electronics_R2&hash=item3a6adce6aaI have used it for over 12 months now, works very well, and if you need to make a "large" board just use two pieces with a slight overlap, works just as well! hope this helps
Rgds
David
--- In Homebrew_PCBs@yahoogroups.com, Philip Pemberton <ygroups@...> wrote:
>
> On 19/03/12 21:18, John Anhalt wrote:
> > Hi Phil,
> >
> > This describes the whole process with cupric chloride: http://members.optusnet.com.au/eseychell/PCB/etching_CuCl/index.html
> >
> > I have been using it for several years. Too much acid leads to undercutting, but the amount of acid is difficult for most DIY'ers to access. Go by specific gravity and color.
>
> OK, it looks like what I've ended up with is somewhat close to that --
> almost black liquid, but with green foam (and foam it does: I had to
> turn the air pump right the way down after it foamed over the side of
> the etch tank and onto the concrete floor!)
>
> There's a slight yellow-brown tint to the green, so there's some FeCl3
> left in there (or at least some iron-based compound), but I don't think
> there's much...
>
> Etch time with air on one-quarter is around 10 minutes, if even that.
>
> Now if only I could get my hands on dry-film photoresist in quantities
> less than "two bloomin' great heavy reels" (which seems to be Mega's
> preferred sales unit, at a cost of £100-odd plus VAT)...
>
> --
> Phil.
> ygroups@...
> http://www.philpem.me.uk/
>