Re: gum question
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- Subject: Re: gum question
- From: Loris Medici <email@example.com>
- Date: Wed, 03 Jun 2009 07:56:29 +0300 (EEST)
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My exposure times are between 3 and 5 minutes (most used being 3:30) with
a bank of UVBL tubes. (Transparency substrate is old stock - not ULTRA! -
Pictorico.) To more facilitate comparison, my 2A:1B Cyanotype standard
exposure time is 06:30 with the same light source and transparency
material. This is true for any gum exposure, tricolor or multi-layer or
gumover doesn't matter.
I haven't started in that direction; I simply landed on 5% empirically. It
was the sensitizer strenght which gave me the best results (with my
materials and strategies) until then. (Had tried 25%, 20%, 15% and 10%
3 Haziran 2009, Çarşamba, 6:52 am tarihinde, Judy Seigel yazmış:
> Thanks Loris... Very interesting... Can you give a general idea of how
> long your exposures are? As I recall, in the old books, where potassium
> dichromate was the norm, it was generally used at 5% (apparently why they
> could keep coated paper for weeks before exposing).
> Of coure, nowadays -- at least around here -- bigger & faster are better
> (or is that just cars?). In any event, can you say what started you in
> that direction? Also, maybe you said & I missed that, too -- is this for
> On Fri, 29 May 2009, Loris Medici wrote:
>> Hi Judy, it's ammonium dichromate. (Was shortened as "AD" below...)
>> 29 Mayıs 2009, Cuma, 3:30 am tarihinde, Judy Seigel yazmış:
>>> On Thu, 28 May 2009, Loris Medici wrote:
>>>> I always had better results (due my particular working style and/or
>>>> materials?) with weak sensitizers; I use only two dichromate strenghts
>>>> and 2%. (AD, 1+1 gum/pigment+dichromate.) I also have 10% on hands for
>>>> unusual situations though.
>>> Which dichromate is that, Loris -- potassium or ammonium ??????