Help! Pottasium Ferracyanice (Farmers Reducer)

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Hi everyone, I just got a bottle of Pottasium ferracyande (farmers reducer) and I am not sure how to mix it. It is in a powder form and I need to know how much do I use to make one quart. I want to use this to bleach out small areas in some clouds by painting it on with a fine haired brush. I understand that it is also quite toxic. Any suggestions? Thanks!!

-- Justin Fullmer (provo.jfullmer@state.ut.us), June 29, 2001

Answers

Potassium Ferricyanide is NOT Farmers reducer, but Potassium Ferricyanide + Fixer is. Applying only Potassium Ferricyanide, will reduce, but it can be redeveloped. With Farmers reducer, redevelopment is not possible. Potassium Ferricyanide is not very poisonous, since the metabolism cannot reduce the cyanide group to do any harm. Recipe: Solution A Potassium Ferricyanide 37,5g Water to make 500ml Solution B Sodium Thiossulfate 480g Water(125°F, 52°C) to make 2 liters

Makes reducer for negative, for prints a very weak dilution is used.

Sol A 3ml Sol B 12ml Water to make 1 liter

good luck, Marc.

-- Marc Leest (mmm@n2photography.com), June 29, 2001.


Oh: I forgot, here is an interesting link

http://www.photogs.com/bwworld/potass.html

Marc.

-- Marc Leest (mmm@n2photography.com)), June 29, 2001.


For local bleaching of prints I use an amount about the size of a pea in a couple ounces of water. It should be a bit more than pale yellow. You'll quickly learn what dilution works best for you. Always better if it's a bit too weak, rather than uncontrollably strong. I never mix more than I'm going to use in one session. A small brush or Q-tip works well (or a cotton ball for large areas), and I do it right in the fixer try- lift the print, bleach a bit, then back in the fixer *before you think it's done*. Bleaching should be very subtle unless you're doing advertisements for a toothpaste company!

-- Conrad Hoffman (choffman@rpa.net), June 29, 2001.

I put the powder in a Rx size eyedropper bottle and fill with water. I add powder until there is some left on the bottom. This is a saturated solution, easy to standarize. I then put one drop of the saturated solution in one ounce of water for use.

-- Gene Crumpler (nikonguy@att.net), June 30, 2001.

Just one note of warning. Keep ferricyanide well away from acids since in reaction with an acid, it will release hydrogen cyanide, pretty poisonous stuff. So, for example, don't try to compound Farmers reducer by adding ferri to a rapid fixer or something since the rapid fixers often contain some acid. Otherwise, ferri is pretty safe on its own, but like all chemicals is best treated with respect. Cheers, DJ.

-- N Dhananjay (ndhanu@umich.edu), June 30, 2001.


Justin:

For the purposes you've mentioned, there is no need to be extremely accurate in mixing the solution. Some people actually mix it until it appears about the correct shade of yellow. For consistency, I like to be a little more accurate than that. I just measure the ferricyanide powder with a set of plastic measuring spoons reserved strictly for the darkroom. I usually use 1/8 level teaspoon per quart of water. You can use more or less to suit your own preferences.

-- Ken Burns (kenburns@twave.net), June 30, 2001.


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