Impurities in Kodak chemicals

[chris_raney1]

<p>I brew up most of my black and white chemicals from scratch, though there are a few I still purchase in the package; one of these is Kodak's standard F-5 powered, hardening fixer that I use with my film. It works wonderfully--of course--and I've used it for many years. But something I've noticed recently that's a little disquieting is that there are tiny little black specs to be found floating in the freshly mixed solution.</p>

<p>I'm meticulous in the way I whip-up my chems, and I have always used distilled water for everything except the washing cycle (though the water is doubly filtered during this process), so these little black nits aren't a result of filthy conditions or improper mixing.</p>

<p>Lo and behold I've seen these same little black specs in the sodium sulfite I purchase from a local chemical supplier that I use in almost all of my chemical solutions. I suspect that stuff comes from China, because the bulk sodium thiosulfate they sell me that I use to make non-hardening paper fixer, does. So am I to gather that Kodak is obtaining this same black-spec-filled sulfite for its F-5, and perhaps it's other chemicals? Or answer me this: are Kodak chemicals now made in China? </p>

<p>Whatever these little nits are I do know they certainly didn't drop out the south-end of north-bound insects, because if they were insect poop with would dissolve quite handily with little problem (might give the film a nice patina...who knows?). And honestly, I filter all of my solutions the day after they've settle down from mixing, so these specs honestly don't present any problem to me.</p>

<p>I'm simply curious. What are my insoluble nits, and where did they come from?</p>

[lars_holtgrewe]

<p>Without thinking into it too much yet, just to get a little more information, are the specs present in a clean beaker you mix the chemicals up in, or do you mix directly into your fix storage container?</p>

<p>If you mix in your fix storage container, silver particles from previous batches? If not, we'll go from there.</p>

<p>On a side note, take a look at TF-5 non hardening fixer. I originally started using it just for paper, but now use it for film as well. Unless you're processing in conditions that require a hardener (long and/or tropical times/conditions) or using a film like efke or adox, with soft emulsions, there's really no need to use a hardening fixer. Even with those films, if you're careful, there's no need for it.</p>

[leicaglow]

<p>I don't suppose they might have been from your pipes would they? I guess you would see it in other chemicals though. I used to have a darkroom with pipes that would get build up and come out as dark gray specs. Drove me nuts because our city's water supply was so good.</p>

[chris_waller]

<p>I've noticed these on the odd occasions I've made up a developer from powder. As a matter of routine I let the solution stand for 24 hours them filter it through a coffee filter.</p>

[profhlynnjones]

<p>I stopped using hardener back in the mid 1950's, it caused lots of troubles and no good points. I also changed from powdered fixers to rapid fixers, the fact that it last longer cancels the increased costs, also if you really want hardened film you simply add it to the fixer.</p>

<p>Lynn</p>

[Alan Marcus]

<p>One of the corner stone's of Kodak is purity of the constituent ingredients. It is a very rare event should Kodak falter on this. Kodak's Fixing Bath F-5 is an update to an earlier formula. The revised receipt contains boric acid crystals as their presence reduces the likelihood that the hardener, potassium alum, will form a precipitate. The precipitant is aluminum sulfate. The other hardener in common usage is chrome alum. Both are multivalent metal ions. Likely, you are seeing sludge of aluminum sulfide.</p>

<p>The formula for Kodak F-5 is in the public domain:<br>

Water 50 Celsius 600ml<br>

Sodium Thiosulfate 240 grams<br>

Sodium Sulfite desiccated 15 grams<br>

Acetic Acid 28% 48ml<br>

Boric Acid crystals 7.5 grams<br>

Potassium Alum 15 grams<br>

Cold water to make a total of 1 liter. <br>

<br>

Now prepared power mixes likely contain property chemical (sequestrants) to aid getting constituents in solution quickly. In addition, pre-packaged formula contains chemicals like calgon and similar that deal with hard tap water. My guess is, your use of distilled water provides noting of these agents to work on, as a result, they go to work on the wrong thing. In addition, keep in mind, a fixer solution will go bad in time regardless, even if not used.</p>

[jpo3136b]

<p>If you want to see fixer dust out, just use plain hypo. I have used the 240 grams of sodium thiosulfate (pentahydrate) diluted; it'll dust out pretty good as it exhausts. In some of the old texts, I occasionally see a warning not to use plain hypo after it clouds; note that this occurs after about six prints. That dusting out takes a while, but when it occurs, the bottom of the tray will be coated in a black sand of those sulphur compounds</p>

[chris_raney1]

<p>I appreciate all the responses, yet, as a teacher I'm rather shocked at the poor reading skills exhibited here. I've explained that I use the packaged F-5 only for film, not prints. Though I should have explained that I do live in a tropical climate, so hardening of the film is important.</p>

<p>However, how can I respond to those who suggested I check my water supply, when I've explained I use distilled? As far as mixing goes, I mix in glass, Griffin beakers, so container contamination is not an issue. I've also mentioned I filter the chemicals the next day. </p>

<p>Hmm...poor grades for most of you; kudos to those who asked pertinent questions related to the information I left unstated. </p>

<p>This still leave the black speck problem unresolved, though. </p>