[Alt-photo] Re: DAS

[Kees Brandenburg]

Hi Loris,

I keep the stock solution in a brown glass bottle in a closed cupboard, at room temperature, for months without seeing any changes. With the DAS Caseïn mixes I premix everything and protect it from light. The pigmented mix is ready to use and also presensitized. I keep this in the fridge in a glass jar with a black photo paper bag wrapped around. I prepare this per 100 ml and use it up before the casein goes bad. Adding thymol can lengthen this period, but this mix holds for several days.

Concerning carbon: I keep my presensitized sheets of carbon tissue in black plastic bags inside archival boxes. Just like photo paper actually. I interleave each sheet with a sheet of paper. I have kept several sheets for months like this at room temperature and they still print fine. I coat my tissue on 200gr yupo and have hardly any curling problems. I am using a 10% gelatin with additional sugar (45 gram per liter) and  glycerin (2,5 ml per liter). Gelatin/DAS ratio is 0.06. This means that for every 100 grams of gelatin I add 6 grams of DAS.

My biggest problem is the drying time of the freshly coated sensitized tissue. It prevents me to turn on normal lights in my darkroom for almost 2 days! I should build a light-tight drying cabinet. Mixing coating and preparing for printing I do under sodium vapor safelights. I have two Osram Duka's and a large French made safe light that carries a Philips SOX sodium vapor lamp. So that's a lot of safe light.

-kees

On 15 apr. 2013, at 13:00, Loris Medici <mail at loris.medici.name> wrote:

> Kees,
> 
> Do you know what is the shelf life of the stock solution?
> Pre-sensitized carbon tissue sounds very nice but how do you manage to
> uncurl the tissue + is it as sensitive to humidity like dichromates?
> 
> Regards,
> Loris.
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