Re: palladium drydown and developer

I think you are right about the refractive effect you are mentioning.
My 'fuzzing' theory was only meant to explain un-treated pt/pd
prints, and explain the phenomenon of Dmax decrease as it dries.
Since an untreated print has no 'layers' per se, I think the fuzzing
may be a part of the reason. That said, your point about a
reflective layer is probably quite true as well, and indeed, that may
be the reason that waxing, for instance, is so effective at making a
print 'snappier'.

All of these remedies are relatively easy to assess for yourself,
requiring only some modest supplies, a stack of throwaway prints, and
a rainy afternoon.

On Jul 21, 2006, at 6:48 AM, Loris Medici wrote:

> Hi Clay,
>
> My take / understanding is: when you coat the paper with some kind of
> reflective medium (gelatine, gum, wax and polyurethane wood finish
> as I do),
> the reason of the darkening and contrast increse in the shadows is
> caused by
> the fact that the higher refractive index of the coat causes some
> of the
> refracting light stay in the layer... Think of the mirror effect water
> causes when the light hits it surface from beneath with angles
> lower than xx
> (was it 38? - don't remember exactly - whatever you understand what
> I mean).
> Since less light is reflected back (and kept in the coating), density
> increases.
>
> Maybe your theory with fibers is also effective in this phenomenon
> but I
> think the actual/main reason/cause of the dmax increase is what I
> describe
> above.
>
> Regards,
> Loris.
>
> -----Original Message-----
> From: Clay [mailto:wcharmon@wt.net]
> Sent: 21 Temmuz 2006 Cuma 13:51
> To: alt-photo-process-l@usask.ca
> Subject: Re: palladium drydown and developer
>
> ...
>
> The other phenomenon that has not been mentioned is the microscopic
> 'fuzzing' of the paper surface that occurs as paper dries. This
> seems to
> affect the dark shadow areas much more. It is really more
> accurately called
> 'dry-up'. If you slap a wet pt/pd print on a reflection
> densitometer, you
> will get a much higher reading (in the
> 1.8 range) than you will a few hours later after it has dried. The
> tiny
> fibers of the paper then stand proud and cause a loss of reflection
> density
> that in the best of cases will give you reflection densities in the
> neighborhood of 1.4-1.5. This is almost a full stop of reflection
> density
> loss.
>
> As to what can be done to mitigate this effect, I have found that
> very light
> gelatin sizing (in the 1% range) can help to a degree.
> Another approach is to deal with this after the print is dry and apply
> either wax or subsequent gum coats. I have a waxed vellum print
> that has
> measured Dmax of 1.9 using several layers of Gamblin cold wax medium.
>
> My personal preference is for additional layers of expose gum,
> since it
> offers so many options for color manipulation of the image.
> Finally, a coat of Liquitex Gloss medium diluted 1:8 will also have
> the
> effect of causing a measurable (though relatively minor half
> stop) increase in Dmax. Again, I think this is because it causes the
> microscopic fibers to lay down and behave.
>
> ...
>
Received on 07/21/06-05:57:39 AM Z