RE: Determining SPT with gum Was: Gums a la Demachy and Puyo

From: davidhatton_at_totalise.co.uk
Date: Wed, 12 Jul 2006 12:15:07 +0100
Message-id: <E1G0cgN-000PAX-BR@webm10.global.net.uk>

('binary' encoding is not supported, stored as-is) Hi Loris,
I intend trying all the suggestions I got back from the list as I am as a babe in
arms. I certainly shall get back with my results. As long as people understand
that I know that I lack authority in this field and that my results may vary
wildly from those garnered by those more experienced than I. :)

>BTW, to all: How do you determine your standard printing time with gum?

Gum, in my experience, can't really be compared with normal (silver, iron,
platinum etc.)photographic processes, there being far more variables inherent in
the way it works.

In the beginning, I determined that I would develop automatically for no more
than 30 minutes. This was purely arbitrary based on information gathered from
books, the list etc..The rest of the process is based on the development time. I
determined the SPT by using a stepwedge and guesstimated exposure time (initially
10 mins.) to attain two solid steps at steps 1 and 2. The all the rest is as the
system says. It seems to work. Although, having said that the RH has shot up in
the last few weeks causing an increas in speed. That's no problem though because
I can develop for hours if I need to whereas for other processes one can't. Oh
oh.. The power has just gone off (first time today - whoopee) - must log off.
Hope this helps. Not very technical I'm afraid, it's all a bit seat of the pants
for me :)

Regards,

David H

  

>
>Since calibrating Argyrotype I determine SPT by overexposing a step tablet,
>then scan it, average the tone in the steps, change the mode of the file to
>Lab, create a new grayscale file from the Luminance channel and use the
>levels adjustment tool with the Alt key to locate the first black square.
>Then I make the necessary exposure time adjustment (by counting steps below
>the first black and reducing the exposure according to this) and retest
>(using the same step tablet along with the CDRP) to see if everything's
>right and to determine the negative color. It was surprising to see that the
>density I was choosing with the former method (visual inspection of the step
>tablet) was often 1-2 steps off (overexposure - I was often choosing an
>exposure time which causes solarisation = less dmax)... What would be your
>comments on this?
>
>Regards,
>Loris.
>
>-----Original Message-----
>From: davidhatton@totalise.co.uk [davidhatton@totalise.co.uk]
>Sent: 12 Temmuz 2006 Çarşamba 11:27
>To: alt-photo-process-l@usask.ca
>Subject: RE: Gums a la Demachy and Puyo
>
>Hi Loris,
>
>I understand what you're saying - a different curve..
>
>David H
>
>On Mon, 10 Jul 2006 16:33 , Loris Medici mail@loris.medici.name> sent:
>
>>Maybe you can add a little ivory black (a very warm black) to your
>>Vienna Red. But keep in mind that the mixture may behave quite
>>differently than the single color.
>>
>>Regards,
>>Loris.
>>
>>-----Original Message-----
>>From: davidhatton@totalise.co.uk [davidhatton@totalise.co.uk]
>>Sent: 10 Temmuz 2006 Pazartesi 12:44
>>To: alt-photo-process-l@usask.ca
>>Subject: Re: Gums a la Demachy and Puyo
>>
>>Hi All,
>>
>>While we patiently wait for Terry to finish his garden..What other
>>pigments would Demachy use for one coat gums? Plus, how do I modify
>>Vienna Red to be darker? Is it possible? I've looked on the internet
>>and the pigment (red Oxide(?))in some images seems to have a darker tone to
>it than mine.
>>
>>David H.
>>
>
>
>
>---- - Madasafish - Voted Best Heavy Consumer Broadband Provider in the 2006
>Internet Industry Awards http://www.madasafish.com/
>
>

---- - Madasafish - Voted Best Heavy Consumer Broadband Provider in the 2006 Internet Industry Awards http://www.madasafish.com/
Received on 07/12/06-05:28:23 AM Z