U of S | Mailing List Archive | alt-photo-process-l | Re: Tricolour gum and PDN

Re: Tricolour gum and PDN

I too can vouch for PDN with tricolor gum...

The first thing I would check is the color space of your image(s); this is
the most common cause of thin negatives that I've seen.  If they're in
sRGB, the resulting negatives tend to be really thin.

If that's the case, start from spittling the channels and convert each one
to Adobe RGB as your first step.  Then invert, curve, etc.

Hope this helps,

Camden Hardy


On Sat, September 2, 2006 2:35 pm, Henry Rattle wrote:
> I wonder if anyone who has used PDN for tricolour gum can help?
> I've made a number of tricolour gums in the past (some examples on the
> alternativephotography site - thank you Malin) but was encouraged to try
> the
> PDN system by Christina's convincing comparisons between tricolours made
> with standard and PDN negatives. (incidentally, I echo the appreciative
> comments for Christina's books - best read since Post-Factory!)
> The PDN process worked perfectly - a cyanotype print with every step of
> the
> 21-step clearly distinguished, and a full range of tones in the print.
> Similar outcomes for one-coat gum.
> However when I set out to make tricolour (or CMYK) gum over cyanotype, I
> run
> into problems. After separating the channels, all three (or four - I've
> tried both RGB and CMYK) negatives seem very thin and flat, so that using
> the full standard printing time I end up with colour layers that are way
> too
> dark. Even diluting the cyanotype solution 1+4 still ends up much too
> dark.
> Yet I note from Christine's workflow that she uses more or less full
> strength classic cyanotype solutions. Am I missing something obvious?
> Any shared experience would be most welcome!
> Best
> Henry