Re: Gum dichromate issue

Thanks Kate,
I should have told you my background first, I am engineer and software
developer and taking pictures since I was 6 years old (I am 54) which I only
read to learn on my own.
Basically I am very good with numbers, my understanding of colors is because
of Newton law and read colors by numbers.
My issue is to apply this (digital?) to gum printing which is not easy (I
need to learn gum).
Unfortunately we all make errors and before redoing the image an option is
to adjust (othewise you/I throw the print, right? But some people keep
them).
The image you sent me is very good and shows (in colors) what I am talking
about and you got my problem, right?
Cyan also needs to be adjusted and in my case this adjustment (most of the
time) is because the lack or excess of yellow.
My theory with magenta is to "see" it the way is coming out during the water
development (the last I apply) and when I see the greens and other colors
that magenta makes that's it.
But then I see the picture either too green or either too blue or yellow
(most of the time as in your image) and I noticed you don't have adjustments
in K.
I go with the RGB but I don't use the K and it might that be the adjustment
issue.
Thanks,
Giovanni

----- Original Message -----
Wrom: IPBARHDMNNSKVFVWRKJVZCMHVIBGDADR
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, August 11, 2004 4:39 PM
Subject: RE: Gum dichromate issue

>
> Hi Giovanni, the inherent nature of gum means that it is imprecise -
> often you DO have to print a layer again...anyway, as far as I know this
> could be improved if you do the following - always stick to the same
> pigments and test them thoroughly for strength. Some pigments are
> stronger in colour for their volume than others. For instance, yellow
> can often print at much greater apparent density than other colours.
> This will upset the colour balance. Cyan is somewhat self-masking, and I
> don't know if this is true for other colours. I assume the more opaque
> the pigment, the more it will self-mask.(any comments???) I have a
> problem with the magenta pigment I use - it's very hard to measure
> accurately (tube paint) and just a little too much throws the balance
> way out. It's hard also to distribute the pigment evenly throughout the
> emulsion - often it will fall to the bottom of the vessel and you will
> get stronger pigment in the last prints. This can be helped of course by
> stirring frequently (remembering to is my problem).
>
> As for reprinting the cyanotype layer - do you double coat? I find I get
> better density that way. Reprinting in cyan might not be a good idea, I
> don't know...someone else will have to answer that. I usually reprint in
> gum if I need to add cyan.
>
> There are so many variables in gum that it's hard to know what went
> wrong - or right. Two identical prints made at the same time can vary
> significantly from one another - it's one of the noted features of gum.
>
> If you have problems with a layer of a specific print, I would try
> reprinting the negative for that layer with greater or lesser density
> depending on the problem. Do you use CMYK or RGB?? I can't remember. OR
> add a little more or less pigment to the emulsion. A great deal of
> personal experimentation is the only way to succeed with gum. And you
> have to be prepared for your prints to not be quite what you expected -
> and accept the differences!!
>
> Did you get that colour chart I sent you and was it any use??
>
> Kate
>
> Sandy,
>
> Thanks for your advices.
> I got some of he books you told me and they are helpful.
> Do you know about other books on negative separation?
> Yes, you are right I will only do it by computer but if you don't
> understand
> well the process then you won't be able to do it well.
> For instance, I always have a print that requires an adjustment or
> reprint.
> How would you do it? Why it always happens with a specific print? Is it
> the
> pigment or is the specific negative layer?
> By the way, when you reprint the cyan and you are following Sam Wang
> paper
> do you do it again on cyanotype? Not with gum?
>
> Giovanni
>
>
> ----- Original Message -----
> Wrom: QBGJSNBOHMKHJYFMYXOEAIJJPHSCRTNHGS
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Monday, August 09, 2004 11:18 PM
> Subject: Re: Gum dichromate issue
>
>
> > There were more than a few full books put out on making separation
> > negatives for the graphic arts. If you like I will try to provide you
> > with full citations. I know there is at least one very good one in my
> > university library and I suspect that if you do a search on a good
> > public or university library in your country you will find the same.
> >
> > However, as someone who has actually made three-color carbon and
> > carbon prints with film separations let me assure you that it takes
> > a lot of time. There is no way in the world I would every think of
> > doing that kind of work again without making digital separations on
> > the computer.
> >
> > Sandy
> >
> >
> >
> >
> > >
> > >
> > >> I do have several questions and probably too many but the first
> is:
> > >> Is there any book you recommend me to read that deals with the
> three
> > >> negatives instead of the Kodak single color negative?
> > >
> > >Good question. The best books on separation practice I recall were
> short
> > >things put out by Kodak that were out of print long ago. I'll look
> through
> > >my photo books and see what I can find. First, you have to separate
> the
> > >colors. Are you intending to make three in-camera negatives, or
> shoot
> > >color film (or digital) and do the separation later?
> > >
> > >The basic issues are (i) getting the color balance right, which is a
> matter
> > >of using the right filters and choosing the right exposure and
> development
> > >for the three negatives [with DT, one often develops the 3 negs to
> > >different contrast levels -- I suspect the same may be true of other
> > >processes]; and (ii) registration of the three [or four, with a
> luminance
> > >layer] negatives. In the old days, we punched holes in unexposed
> film
> and
> > >used pin-registered film holders, enlarger negative holders, and
> printing
> > >frames throughout the process. Condit, the manufacturer of
> > >pin-registration equipment, went out of business a few years ago. I
> > >understand that shrinkage is a factor with multi-layer gum, so
> registration
> > >may be more of an issue for you than it is for DT printers.
> > >
> > >Best regards,
> > >
> > >etienne
> >
> >
>
> ---
> Incoming mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.732 / Virus Database: 486 - Release Date: 29/07/2004
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.732 / Virus Database: 486 - Release Date: 29/07/2004
>
>
>
Received on Wed Aug 11 19:19:15 2004