Re: Why multiple exposure (was Re: (Gum) Tonal scale)

I sent this 24 hours ago and it never came back, even though posts I
sent later did arrive, so I'm sending it again. I added something, as I
always think of more things to say later, so if the other one ever
comes around, it will be slightly different.

On Dec 2, 2005, at 10:30 AM, Katharine Thayer wrote:

> Loris and all,
> This is the kind of tonal scale that I routinely get with saturated
> ammonium dichromate and a strong mid-dark pigment like thalo, mixed
> the way I like it. It's a well-established fact that the more
> dichromate, the longer the scale; the less dichromate the shorter the
> scale, and in my own tests, that are available somewhere on my
> website, I found that to be true. When I diluted the ammonium
> dichromate to 5%, the number of steps I could get was cut in half
> from what I could get with the saturated dichromate (and the exposure
> was 5x as long). But Loris is getting the same kind of scale with 5%
> ammonium dichromate as I get with saturated dichromate. I think
> probably he is a wizard. But this just emphasizes the truth that you
> can never say ANYTHING about gum and make it stick. I never could
> understand why people would want to print with diluted dichromate and
> give up the steps, but apparently it's not always the case that you
> give up steps to print with diluted dichromate.

Another variable that affects the number of steps is the kind of gum.
When my favorite gum was discontinued and I was testing gums for a
replacement a couple of years ago, I tested two dark gucky gums (that's
a technical term of course) and four clearer gums. With repeated tests,
everything else held constant, the dark gums reliably printed with
fewer steps (5-6 with whatever pigment I was using) than the clearer,
purer gums (7-10).

>
> Funny, in the grey ambient light of yesterday your upper steps looked
> perfectly white to me, but in the brighter sunnier light of this
> morning, I can clearly see the pigment stain you were talking about.
> Katharine
>
>
>
> On Dec 1, 2005, at 12:24 PM, Loris Medici wrote:
>
>> BTW, I've uploaded the scan of the test. Any comment would be
>> appreciated.
>>
>> http://www.loris.medici.name/Gum-Test-01.jpg
>>
>> It looks like there's some staining (unsized Whatman HP watercolor
>> paper) -
>> both pigment and dichromate stain (the latter being greenish - I
>> guess it
>> will clear in metabisulfite... But I will try to size the paper
>> first).
>>
>> Regards,
>> Loris.
>>
>> -----Original Message-----
>> From: Loris Medici [mailto:loris_medici@mynet.com]
>> Sent: 01 Aralık 2005 Perşembe 21:47
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: RE: Why multiple exposure (was Re: (Gum) Tonal scale)
>>
>> Hi Katherine. I was talking about one color / one layer of the
>> tricolor. The
>> test I did was one coat, one color. I mention tricolor just because
>> I'm
>> making tests in order to make tricolors in the future.
>> ..
>>
>
Received on Sat Dec 3 10:27:30 2005