Wayne wrote:

Wayne wrote:


wrote:


"Hydroquinone: To increase the print contrast add 100ml per liter of
working developer."

How does one make a 10% solution of this photo chemical?

the quote comes from,

http://www.jackspcs.com/pitone.htm


Unless you are going to use it immediately you will probably want some
sodium sulfite in this 10% solution too. Its best to start with less
than 1000 ml water and add water to make 1000 after dissolving both the
sulfite and HQ. Otherwise you may end up with slightly more than 1000
ml, and hence a slightly weaker solution. It probably wont make much of
a practical difference in this case but its a good practice to get
into. I'll let someone else suggest how much sulfite you will need.




Since the others seem to be occupied, I will recommend adding roughly
30 grams of sodium sulfite to preserve your 10% solution. Jackspsc
recommends adding some sodium bisulfite too, which may be helpful but
it is probably optional if you dont happen to have any laying around.

HYDROQUINONE SOLUTION
Chemical Amount Units
Water (125°F/52°C) 750 ml
Sodium sulfite 25 g
Sodium bisulfite* 5 g
Hydroquinone 10 g
Water to make 1000 ml

* The sodium bisulfite is not in the original formula. Maxim Muir
recommends it to buffer the hydroquinone solution.
http://www.jackspcs.com/pd130a.htm



That is only 1/10 %.
If you want a long lived solution of hydroquinone without preservative,
use Propylene glycol instead of water as the solvent. Hydroquinone,
pyrogallol, paraminophenol base (not the hydrochloride), and
pyrocatechol are all soluble enough in glycol to make a 10% solution
which will then dissolve in water. By 10% I mean 100 grams dissolved in
enough glycol to make 1 liter.