Re: Chrysotypes and humidity

[Lukas Werth <lukas.werth@rz.hu-berlin.de>]

Cor,

the drying over calcium chloride also seems to take care of unwanted
precipitation. Some dammage might occur if you leave the paper too long
particularly over ammonium chloride.

Just enough fluid is needed to cover the bottom. Be careful to mix the
calcium nitrate: it needs little water to dissolve in, and we need a
saturated solution. I ordered one Kg and poured too much water over it, so
I had to order a second Kg. 

The gold precipitates easier if less ligand is used to accommodate
contrasty negatives. 

One more suggestion: if you use John Rudiak's/Tony McLean's instructions,
do not mix the gold chloride with the sodium hydroxide beforehand: it will
not be stable, but change/go bad after about two months. The same is true
for Sol. B (the ligand), so mix only a small batch. 

Lukas



At 11:26 15.08.01 +0200, you wrote:
>
>Lukas,
>
>Thanks for below suggestion, I assume that bringing a coated Chrysotype
>to the desired humidity for upto 1 hr hasn't any negative effects on the
>coated paper (I could imagine "precipitation" of the gold, since the
>ligand (TDPA)-gold complex is said to be instable)?
>
>And what volume of solutions do you put in these trays?,
>
>Thanks,
>
>Cor
>
>> Cor,
>> 
>> I have cat litter trays with saturated solutions in them for humidity
>> control. Ammonium chloride for 85%, calcium nitrate for 65%, calcium
>> chloride in powder form ca. 10%, in sat. sol. ca. 40-50%(?), all ideally 20
>> C, which means for me room temperature. The paper is taped on the lid (a
>> laminated fiber sheet). I usually dry the paper first over calcium chloride
>> powder, and then bring it to the desired humidity over the other solution
>> (over each between 1/2 h and 1 h).
>> 
>> Lukas
>