Kodak SH-1 Formalin Hardener for Films and Plates

[FilmIs4Ever]

FilmIs4Ever submitted a new resource:

(there was a url link here which no longer exists) - Kodak SH-1 Formalin Hardener for Films and Plates

Water - 16 fl. oz. - 500mL - 20 fl. oz.
Formalin (40% Formaldehyde solution) - 2 1/2 fl. dr. - 9.75mL - 3 1/8 fl. dr.
Sodium Carbonate - 73 grains - 5g - 87 1/2 grains
Water to make - 32 U.S. fl. oz. - 1L - 40 Imp. fl. oz.

U.S. Customary units given are exact. Metric measures are accurate to within 250µL or 250 mg. Imperial units accurate to within 1/4 gn., 1/8 fl. dr.

NOTE: SINCE THIS FORMULA WAS PUBLISHED, FORMALDEHYDE HAS BEEN CLASSIFIED AS A PROBABLE CARCINOGEN, AND EXTREME...

(there was a url link here which no longer exists)

 

[Photo Engineer]

Common Formalin is actually about 37% and the formula I have contains 50 - 100 g/l of Sodium Sulfate.

PE

 

[FilmIs4Ever]

Hey, Ron, so would that require an adjustment of this formula? I assume that they either got lazy and rounded it to 40% or the concentration may have been changed since this was published in 1947.

 

[Photo Engineer]

Actually, my formula used 10 ml/l of 37% formalin and the pH was stated to be 9.5 - 10.1 in the formulas I have in my notebook here.

PE

 

[FilmIs4Ever]

So is the pH for the SH-1, or the formalin soln. you add to it? As is indicated, the formula I have is originally in U.S. Customary, so it's possible they just carelessly rounded to the nearest half fluid dram when they converted it from a formula originally written in cgs units, which accounts for the shift down when I converted back. IIRC, it was actually somewhere in between 9.75- and 10mL, and I just rounded to the nearest 250µL. I'd assume that the formalin is actually the same in both cases and they just rounded to 40% in the book I have. Converting the amount in a 40% solution to 37% gives about 10.5mL equivalent so that isn't the reason for the difference in the amount. Again, it's probably a matter of my formula having less exact rounding than yours does.

Is the Na-Sulfate in addition to- or as a replacement for the Sodium Carbonate.

I've noticed that there are more than a few examples of Kodak formulae, published by Kodak or allegedly taken straight from Kodak that are modified over time, without any indication.

 

[Photo Engineer]

The pH of the hardener should be alkaline and varies slightly due to the fact that unstabilzed formalin can oxidize to form formic acid as a contaminant. This causes some variation in pH. I used to adjust the pH to the pH of the developer I was using.

The sulfate is in addition, not in place of carbonate as the solution should be buffered with an alkali.

The hardener I refer to may be a different formula number, it is just the preferred one we used in-house.

PE