RE: Two carbon questions

Loris,

Yes, that is a good methodology to follow.
Whenever I test something I try to devise the
test so as to derive as much information as
possible. This saves time in the long run.

How are you pouring the tissue? Will you be using
some type of frame as I describe in my book? If
so, this will allow you to coat with much greater
height.

However, remember that real thick coating require
longer exposure times. Consider the following
examples, both of which produce good prints.

1. Tissue made by coating a 11X14 base with 75ml
of an 8% 250 bloom gelatin, heavily pigmented.
2. Tissue made by coating a 11X14 base with 150ml
of a 12% solution, lightly pigmented.

Exposure for No. 1 to get maximum Dmax is about 300 units.
Exposure for No. 2 to get maximum Dmax is about 1200 units.

Sandy

>Actually I was planning to make small batches of
>glop w/different amnts. of pigment and coat them
>onto paper (thickness = 1mm) to visually
>determine the minimum amnt. of pigment giving
>the necessary (acceptable) density (and use
>slightly more pigment -> 5% more for instance -
>since I won't / shouldn't expose deep to the
>bottom). A ballpark figure will save much time
>in this type of testing... Do you find this
>approach logical?
>
>Regards,
>Loris.
>
>-----Original Message-----
>From: Yves Gauvreau [mailto:gauvreau-yves@sympatico.ca]
>Sent: 13 Nisan 2006 Pers¸embe 15:34
>To: alt-photo-process-l@usask.ca
>Subject: Re: Two carbon questions
>
>Loris,
>
>I can't help you much on most of this but I have
>been thinking lately about how much pigment to
>use in g/100ml (or % if you prefer) all this
>base on a constant Dmax I want to achieve
>whatever the tickness.
>
>I came up with the following formula:
>
>Pigment concentration = K/Tickness
>
>where
>Pigment concentration you need is in grams/100ml
>K is in milligrams of pigment per cm^2. This
>value is the amount of pigment in milligrams you
>need on a 1 cm by 1 cm square such that the
>reflective density is what you want to achieve
>as Dmax. You will need a bit more then
>this depending on how deep your exposure will
>reach. I still have work to do to factor relief,
>exposure and % dichro.
>Tickness (wet) is in millimeter (mm)
>
>You can adjust K such that it will take into
>account that only part of the tickness of the
>emulsion will be left on the final print and
>thus reducing Dmax. From the recipes given here
>and elsewhere K would seem to be around 3
>mg/cm^2 which give pigment concentration ranging
>from 2 to 12 grams per 100ml for tickness
>ranging from 0.25 to 1.5. Based on these number
>to get 1mm wet tickness you would need 10 grams
>per 100ml but but but this doesn't account for
>relief and it isn't even base on actual measure
>of densities.
>
>Regards
>Yves
>
>
>
>
>----- Original Message -----
>From: <mailto:mail@loris.medici.name>Loris Medici
>To:
><mailto:alt-photo-process-l@sask.usask.ca>alt-photo-process-l@sask.usask.ca
>Sent: Thursday, April 13, 2006 7:12 AM
>Subject: Two carbon questions
>
>I plan to make a normal contrast tissue using
>indian ink. I want to prepare the gelatine +
>sugar + ink solution beforehand (will coat the
>tissue later). Sandy's carbon and carbro book
>says that the gelatine solution can be
>refrigerated for later use (remember reading
>this somewhere else too). I tried to refrigerate
>gelatine solution once (about 250ml, 10%) and
>after about 2-3 weeks in the fridge, the water
>was evaporated completely leaving only dry
>gelatine in the bottom of the vessel - it was
>fun to play with the dry gelatine disk later ;)
>
>1) Does it mean that I have to fridge the
>gelatine solution in a hermetic container? (I
>guess yes but I want to hear others would say...)
>
>2) Won't heating the gelatine solution before
>coating or leaving it about 2 hours in a warm
>water (45C) bath to have the bubbles expelled
>(after adding the pigment and stirring
>vigorously) reduce water in the solution (due
>evaporation) considerably? How this will affect
>the working characteristics of the solution? Am
>I thinking too compulsively?
>
>I plan to start with batches of 500ml... I aim
>for a tissue with normal contrast / moderate
>relief. (Any suggestions for pigment quantity? I
>want to make a tissue with 1mm wet thickness.)
>
>TIA,
>Loris.
Received on Thu Apr 13 08:34:18 2006