Re: clearing carbon prints

Hans Nohlberg (chiahans@tripnet.se)
Mon, 13 Apr 1998 16:46:13 +0200

Phillip Murphy wrote:

>> It may have something to do with the characteristics
>>of the gelatin being used for printing that necessitates
>>"clearing" for some using plexiglas to develop carbon
>>transfer images and not for others.
>> I for one always find it necessary to use a clearing
>>bath for monochrome carbon . If one carefully inspects
>>a cleared print on plexi next to an uncleared one
>>( while dry ) against a white background one may see
>>that there is indeed a need to clear. Otherwise ,
>>please let me know the source of your gelatin supplier
>>so that I can eliminate this step.

Sandy King wrote

>It would be interesting to see the results of actual tests. It may, as you
>suggest, have something to do with the characteristics of the gelatin: it
>may also simply be a question of how long the image on plexi or polyvinyl
>is left to wash.
>As for gelatin sources, I have used, among others, the following gelating:
>Knox; a 175 Bloom gelatin from US BioChemical Corporation; a 100 Bloom
>gelatin from Formulary; and a 250 Bloom gelatin from US BioChemical
>Corporation. I have strong reason to believe that these were all porcine
>skin gelatins, and I never had any reason to clear after washing when using
>polyvinyls supports.

Luis Nadeu wrote

>I would reword it this way. "With some people's 3CCs (tricolor carbons) it
>is necessary..."

It seems that there is at least one person more with the same "problem".
Perhaps this a new topic to examine. It might have something to do with the
combination of gelatin/bichromate/water.
We are using a 230 Bloom acidprocessed porcine gelatin/ potassium
bichromate (puriss) from Merck/ boiled tapwater when preparing solutions
and tapwater directly when developing.
Or, if you of some reasons, find it necessary to clear the carbon print,
why not do it.
Our reasons are: As Phillip Murphy wrote, we can see the differense. Our
soluble temporary support is very yellow on the backside, and if we leave
it hanging in a room with a lot of daylight it is almost impossible to do a
succesful final transfer, it has hardened.
The Carbon process never stops to confuse you ;­)

Hans