Re: Re: For those who are interested in making digital negatives using pigmented inksets

Loris,

Are you sure adding tartaric acid increases contrast? I added more tartaric acid once in order to
dissolve the silver and found it decreased the sensitivity but did not find an increase in contrast.

Sam Wang

> From: Loris Medici <loris_medici@yahoo.com>
> Date: 2004/01/02 Fri PM 06:36:49 EST
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: For those who are interested in making digital negatives using
> pigmented inksets
>
>
> > However, 8-10 minute exposures seem incredibly long to me for digital
> > negatives, considering your set-up, i.e. high output tubes used at 3"
>
> I agree. It's long. As you make this remark I realized that my Van Dyke
> chemistry is not standard:
>
> Solution A: 27gr Ferric Ammonium Citrate + water to make 100ml
>
> Solution B: 6gr Tartaric Acid + water to make 100 ml (the standard formula
> is 4.5gr)
>
> Solution C: 12gr Silver Nitrate + water to make 100ml
>
> As you can see the amnt. of Tartaric Acid is 50% more than the standard (to
> increase contrast). Can be this modification causing the speed loss?
>
> > from the printing frame with close spacing. My set-up for the tests
> > described in my article on UV light sources was normal output bulbs
> > used at about 4" from the printing frame. Also, as you can see from
> > the tests the first maximum black is at about Step 3 or Step 4,
> > indicating that the tests received about 1.5 to 2.0 stops more than
> > needed. And these results pretty much agree with my current work
> > conditions as typical exposures for VDB and kallitype with my bank of
> > BLB tubes is in the 2-3 minute range for digital negatives with a UV
> > printing density of about 1.8 (from about 0.20 to 2.00).
>
> One more interesting fact is that if I vary the exposure considerably
> results don't change by the same proportions. For instance once I tried 8,
> 12 and 16 min. exposure with the same lith negative and only midtones and
> highlights were affected - highlights more; as if the emulsion was self
> masking? What can be your comments for this phenomenon?
>
> Regards,
> Loris.
>
>
>
Received on Fri Jan 2 19:01:57 2004