Fixer mixing question

I just bought a couple of Kodak 1 gallon fixer packets (dry chemical) and the instructions dictate mixing in water that is between 64-78*F. In Tucson at this time of year the "cold" water tap produces water at about 95*F.

How critical is the mix temperature? Would I degrade the fixer by mixing it at the higher temp?

If it is critical I can wait as I won't be processing film until later tonight after dark. I put a gallon of water in the fridge and I can easily wait until it reaches the suggested temp before mixing.

you could do either one. The 95* won't kill it or anything, but you sure don't want to put your prints or film in at that temp.

But, since you already have the water in the fridge, just use it.

Ice in plastic bags works faster by the way.

The older (circa 1940 - 1946) Kodak fixer mixing instructions called out a fixer mixing temperature of 125 degrees F. (Kodak Data Book On Formulas And Processing, 1946).

For film processing, Kodak recommended that all of the processing solutions (including the wash water) be at a temperature of 68 degrees F. From experience, I know that I can process sucessfully at solution temperatures up to 75 degrees F. You can use a water bath to keep everything at the same temperature. I have found Plastic film cannisters filled with water and frozen to be very useful in maintaining water bath temperatures in the range of 68F to 72F.

BTW, when I was living in Yuma, we would drive over to Tucson to cool off.

BTW, when I was living in Yuma, we would drive over to Tucson to cool off.[/QUOTE]


I hear you. The daily 105-110*F around here is not pleasant but it is cooler than Yuma. The last time I went through there was at 1:00 am and it felt like stepping into a pizza oven.

Alexis Neel said:

you could do either one. The 95* won't kill it or anything, but you sure don't want to put your prints or film in at that temp.

But, since you already have the water in the fridge, just use it.

Ice in plastic bags works faster by the way.

Click to expand...

Thanks for a quick reply to all who responded.


I use a variation of that theme when I develop. I have quite a few ice packs which I use in the bath for the developer/fixer when I get to that point. It did not occur to me that the same could easily be done for the intitial mixing. Duhh!
But I'm not in the same kind of hurry at this point so I will check the water in the fridge in a bit and see how it is doing.

Mixing the fixer will go faster and easier at the higher temperature (up to 125F). Use enough warm water to get all the dry chemicals into solution, then mix in enough cold water to make up the total volume required.

Tom Hoskinson said:

Mixing the fixer will go faster and easier at the higher temperature (up to 125F). Use enough warm water to get all the dry chemicals into solution, then mix in enough cold water to make up the total volume required.

Click to expand...

Or ice

I believe the lower water temperature recommendation is to prevent the thiosulphate from reacting with the alum in the mixture to form sulphur sludge.
Hotter temperatures during the preparation tends to cause this with some non-Kodak fixers.

ZorkiKat said:

I believe the lower water temperature recommendation is to prevent the thiosulphate from reacting with the alum in the mixture to form sulphur sludge.
Hotter temperatures during the preparation tends to cause this with some non-Kodak fixers.

Click to expand...

That may be true with some brands of fixer, but we are talking about a Kodak fixer here. Mixing at 125 degrees F should not cause a problem (with Aluminum Sulfite sludging) unless Kodak has made a change in their fixer recipe. In the teaching darkroom I've mixed many gallons of Kodak F-5 at 125 degees F with no sludging or other problems of any kind.

If you are uncertain about Kodak's most current Fixer products, Call Kodak and ask:

Kodak Information Center
9 am - 7 pm
Mon-Fri

1-800-242-2424 ext. 19

http://www.kodak.com/global/en/service/contactKodak/kodakPhoneNumbers.jhtml

Tom Hoskinson said:

The older (circa 1940 - 1946) Kodak fixer mixing instructions called out a fixer mixing temperature of 125 degrees F. (Kodak Data Book On Formulas And Processing, 1946).

Click to expand...

I think the older Kodak non-rapid fixer formulae used sodium thiosulfate pentahydrate. This form of thiosulfate would lower the solution temp significantly when dissolving into water, and so you would want to use a warm water to prepare the solution to facilitate dissolution.

I haven't checked Kodak fixer for some time, but when I checked last, the packaged powder fixer used anhydrous sodium thiosulfate. This can be dissolved in room temperature water, or slightly warmer water with no dropping of temperature. So I suspect this is why they changed the recommended water temperature for preparing the solution. As you said, I don't anticipate a real problem coming from higher temperature water here, it just takes some work to drop the temp to the processing point.

The maximum processing temperature depends on the film. Most films made by Kodak, Fujifilm and Ilford would sustain 38˚C processing temp, as they are designed to take machine processing temp. Fixing process is more efficient and faster at a higher temperature. But some films (like infrared films, x-ray films) and films from other manufacturers may barely take 20-25˚C processing temp.

If I lived in the area where cold tap water is no cooler than 30˚C, I'd stick with Kodak or Fuji films, and developers that give excellent image quality when processed at 25˚C or even 27˚C (such as Kodak XTOL or DS-10 1+2, DS-12 2+1 or 1+1), and use 25-27˚C for dev, 30-35˚C for stop and fix. Just be gentle during processing, and those films should be fine at this range of temperatures.