Saturday, February 5, 2011

More about measurements.

More about measurements :

Standard recipe from Reinhold, Coffenol CCH :

Water 750 ml
Washing Soda 54 gram
Ascorbic Acid (E300) 16 gram
Instant coffee (Brazero) 40 gram
Potassium bromide (KBr) 0.75 gram

Top up water to 1000 ml (1 litre)

This recipe is OK as it stands, but few dev. tanks is 1 litre.
I have solved this problem with stock bottles, i.e. 1 litre bottles with 3X concentration, in use I measure out 1/3 of the tank volume from each bottle and are ready to go in minutes. Only problem is that neither Vitamin C nor Coffee keeps well in a bottle.

So to get a practical 1-tank solution, one must measure out enough of each chemical in question.
Not everyone has a prescise and repeatable weight that will weigh out small amounts.
And a practical solution is needed.

Americans advocate teaspoons, which are frowned upon by europeans. Howevere weight measure by volume is both highly accurate and repeatable, once the homelesson is done.

Homelesson : Find out what a "teaspoon" weighs of each chemical.

This is in fact very simple, set up a thrusty weight, measure out by teaspoonfuls, lets say repeat this 3 times, and find the average measure. This will be very accurate and very repeatable.

MY particular chemicals are as goes:

Washing Soda : 5.63 gram per teaspoon
Vitamin C powder : 2.65 gram per teaspoon
Instant Coffee : 1.80 gram per teaspoon

Homelesson : decide how many teaspoons are needed for one tankful :

My Jobo tank needs 240ml for one 35mm film
My Paterson tank needs 290ml for one 35mm film

Since Kaffenol is vulnerable to air bubbles clinging to the top of the film strip I add a little extra volume.

ONE TANKFUL FOR 1 35MM FILM : 320 ML (11 us FL. OZ.)

Washing Soda 17.3 gram
Ascorbic Acid (E300) 5.1 gram
Instant coffee (Brazero) 12,8 gram
Potassium bromide (KBr) 0.24 gram

Water to 320 ml (11 us fl oz)

Translated to US measures and tablespoons we have :

Washing Soda 3.1 tsp
Ascorbic Acid (E300) 1,9 tsp
Instant coffee (Brazero) 7.1 tsp
Potassium bromide (KBr) 0.24 gram

Water to 320 ml (11 us fl oz

Kaffenol 32-II.1

Washing Soda 3 tsp
Ascorbic Acid (E300) 2 tsp
Instant coffee (Brazero) 2 tblssp 1 tsp
Potassium bromide (KBr) 0.24 gram

Water to 11 OZ

This is a very practical way to mix this developer, and very accurate too:

Just take 8 oz of water

Add 3 tsp of soda, one by one while stirring vigorously until each is dissolved.
Add 2 tsp of Vitamin C powder (NB Ascorbic Acid (E300), not sodium or calcium ascorbates!!!)
Add 2 tablespoons, plus one tsp of instant coffee, stir well and wait until bubbles have dissipated.

Add 0.24 gram of KBr (more on that later)

Top up to 11 OZ (ca 320 ml of water) and use the developer as normally.

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