[alt-photo] Re: gum curve question

[henk thijs]

.......... forgot to mention one important thing: the reason i want to do this is the fact that i make my digital negs on non-transparent plotterfoil, that means times for gum about 700 secs, for (brom)oil printing about 1600 secs and it is not suitable for cyanotype.
Using it for interpositives with the APHS film my times are something like 70 and 160 secs , and i can make tri-color gumprints like Sam does: a cyanotype as the cyan-layer.
Henk
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www.thijs-foto.com
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On 18 aug 2010, at 22:35, Paul Viapiano wrote:

> Don,
> 
> I'm guessing that Henk wants to make a digital interpos to print on to APHS film to make a final neg, thereby eliminating the need to make a wet-step positive.
> 
> Henk, you could always try this and see what happens. Usually an interpos is made with much less contrast, so that final contrast can be controlled in the making of the interneg. You're looking to make color seps for tricolor this way, right?
> 
> Paul
> 
> 
> 
> 
> ----- Original Message ----- From: "Don Bryant" <donsbryant at gmail.com>
> To: <alt-photo-process-list at lists.altphotolist.org>
> Sent: Wednesday, August 18, 2010 12:03 PM
> Subject: [alt-photo] Re: gum curve question
> 
> 
>> Henk,
>> 
>>> 
>> Dear List,
>> Using the gum-curve via PDN to create digital negatives, the following
>> question came up:
>> Cleaning 'old-analogue-stuff' i found still a lot of Arista APHS film, so i
>> want to use it.
>> Making a digital positive and sandwich it with the APHS.
>> Now i was wondering about what curve to use: the one found with PDN making
>> digital negs is based upon UV-blocking of the ink used by the printer, but
>> for the sandwich 'normal' light is used to obtain the neg.
>> The question is what curve is to be used for the positive?
>> Now i tried the following : invert the positive, apply my 'PDN' curve,
>> invert again, sandwich and the result is a APHS negative.
>> Gum looks ok, but before going in tri-color printing i am open for any
>> suggestions :-)
>> regards
>> 
>>> 
>> 
>> 
>> 
>> I don't know about everyone else but I'm confused as hell about what you are
>> attempting to accomplish or do. Can you run this by us one more time with a
>> bit more clarity?
>> 
>> 
>> 
>> So sorry to be so dense,
>> 
>> 
>> 
>> Don Bryant
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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