Re: gum curves

Hi Kees,
I am, for the testing, just using my former pigment concentrations that I
have standardized, so yes, they don't vary. They are what I've used for the
last two years.

I will take note of this below, though, because technically with gum it is
said that reducing pigment lowers contrast, etc. etc. but I have never
tested that to see if it is true. Seems you have, though, from below;
thanks.
Chris

----- Original Message -----
From: "Kees Brandenburg" <ctb@zeelandnet.nl>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, November 07, 2005 8:23 AM
Subject: Re: gum curves

> Hi Chris,
> Did you also find a relation between pigment concentration and curve
> shape? I noticed that an underpigmented mix needs a lot more correction in
> the curve than a higher pigmented one. So deciding on the maximum
> pigment/gum ratio that does not stain and keeping that constant is also an
> important step in the digital gum workflow. And different for each colour
> too.
>
> kees
>
>
>
>
> Christina Z. Anderson wrote:
>
>> Hi all,
>> Gees--subject line sounds like a sex spam for an old folks home..
>>
>> This weekend I was a curve maniac. Anything to divert myself away from a
>> nude powerpoint with 265 slides to input and organize.
>>
>> A number of months ago I was working out gum curves and then I had to
>> move from the South. That work just got resumed this weekend. I was
>> testing, doing all my curve work with Nelson's PDN system, to see if,
>> with gum, the colorized neg makes any difference over black ink only
>> negs. In the past I always used the PhotoWarehouse OHP at about 1/3 or
>> even less the cost of Pictorico, and that accepts black ink well, but
>> color puddles. Hence, monetarily I would much prefer to stick with
>> PWOHP.
>>
>> One other problem I have with Pictorico aside from cost: it is such a
>> thick base that it is the only substrate i have ever had problems with
>> not being in contact with my paper and producing fuzzy spots. The PWOHP
>> is so flimsy (and stretches, sometimes, in the printer) that it remains
>> closely in contact with my paper in a contact printing frame. I do not
>> have a vacuum easel :(. So if there are any waves in the paper from
>> moisture or what have you, you have to watch this.
>>
>> Consistently I have found this: magenta and yellow and cyanotype all
>> have different curves with both black ink only and with colorized inks.
>> So I can pretty much say with surety that I will, upon splitting my
>> channels for my tricolors, curve each individual color's neg separately.
>> That's the charm of the PDN system is its ability to make custom
>> curves--i did 6 over the weekend.
>>
>> I need mention that PDN was not designed to use black ink only so I am
>> bastardizing Nelson's system (sorry, Mark)...but I figured that I needed
>> to find correct curves for the black ink only negs, too, to give an
>> honest comparison.
>>
>> I think I may say, too, that, oddly enough, each color's curve in black
>> ink and in a colorized neg is similar in shape, but maybe not the same.
>> I have no idea what this means. But cyanotype is very responsive to
>> black ink only, in fact, probably too much so. And, the curve shape is
>> similar with each color within the pigment family, e.g. cad yellow and a
>> transparent yellow
>>
>> Today i begin printing side by sides of colorized and black negs, but
>> it'll take a couple weeks to finish and post results.
>>
>> I still am planning on testing Lehman's hydroquinone hardener, but
>> that'll be when I run out of my current batch of sized paper.
>>
>> Bob, so nice that you posted the stuff about grainy cyano--I have had
>> that at times, too, for some unknown reason.
>>
>> Oh, it's a monday!
>> Chris
>>
>> PS OHHH question, how do you deal with the areas of midtone sky that
>> print out in uneven strips of density--what is that called??
>>
>>
>>
>>
>
>
Received on Mon Nov 7 09:36:47 2005