silvergrain chemicals

http://www.youtube.com/watch?v=ArDFVEikL8k

There are two major places where you have to fight in the patent process. One is to fight with the examiners to prove they are wrong (if they are) and another is to litigate.

The examiners are very tough but they don't always know what they are saying. Sometimes they make good judgment but not always. Sometimes you are SOL. What matters more is not just to have a good lawyer but also you (the inventor) become very familiar with the process of getting a patent.

Anyway, in the case of Tektol developers, I had enough design parameters to avoid all those patents so I'd rather do that than spend money and time to fight. I'd be happier if they gave up some of the patents they are not using though.

Another surprising thing is that there is a patent assigned to Kodak that names triethanolamine and salicylic acid (not as the main part of their claims but in the detailed description) that came way after I started using these compounds (as you can confirm online by searching my past postings elsewhere---this predates APUG). The patent has not much useful content and I'm not bothered by its offensive legal power, though.

Ryuji said:

How did you measure the tray life? Do you have rough estimate of how many milliliters of solution and how many square centimeters of air surface? Also, what was the average testing temp?

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No measurements involved. I'm simply reporting the results of my direct observations. No idea what the average temperature is other than the temperature has ranged between 65F and 70F.

It is true that Tektol developers, especially Tektol neutral tends to take a bit more time to develop if you compare to Dektol stock or 1+1, but the reason why water bath technique doesn't work is primarily due to the difference in the developing agent. Hydroquinone is retained within the emulsion longer than ascorbate when the paper (or film in the case of film developer) is removed from the developer and immersed in plain water or alkaline bath. In my early days of experimenting with ascorbate, I also tried to make two-bath film develoeprs with ascorbate, but for this reason it does not work (well, I didn't know the reason at that time but now I do).

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Dektol doesn't work with a water bath either. When the waterbath doesn't work, one has to adjust developer dilution. The only developers I have used that do allow the water bath are amidol (best in this regard), PPPD, Agfa Neutol WA, and PF 130.

True. I could make it to match the developing speed, but I thought it would be more important to make the neutral version (TND) really cold, solid black, and make it mixable with the standard version (TSD) so that people who want half cold developer can make it by simply mixing them.

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Nothing wrong with the difference in speeds. Its just an obvious difference that I note for the benefit of those who may be thinking of trying Tektol. Of the two, I actually liked the neutral version best for some unexplainable reason.

Again, I'm curious to know how you compared TSD with 130...

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Again, nothing but direct observations of results obtained in my home darkroom. No strict controls of any kind. Water used is whatever comes out of the faucet. I do note the date whenever I mix something up as well as noting the date I open the stock solution container. I mixed my first bottle of PF 130 in January and used it through March. The only real reason I tossed it is because the original liter had diminished too much in volume from carryover to adequately cover the paper during development.

Alex Hawley said:

No measurements involved. I'm simply reporting the results of my direct observations. No idea what the average temperature is other than the temperature has ranged between 65F and 70F.

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Ok- I was just curious to compare your test condition to mine.

If you use larger air contact area per volume of developer, the developer will go off faster, of course. So this factor has to be held fixed for a fair test. Also, developers last longer if they are kept at a lower temperature. My tests are done at the ratio comparable to 600 square centimeters per liter of working solution (about the same as holding a liter of solution in an 8x10 tray) at 25C or 77F. I think my test condition is a good approximate to real life situation and if there is any error, my test is more difficult condition than real life due to slightly higher room temp.

(In reality, the actual test situation is simpler than it may sound. I keep the developer solution in a beaker to the depth of 1.7cm, regardless of the beaker size.)

Nothing wrong with the difference in speeds. Its just an obvious difference that I note for the benefit of those who may be thinking of trying Tektol.

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I don't think so either. If you prefer faster development, you could make the developer more concentrated. This would make the image tone even cooler. However, based on the feedback I get, more people actually prefer to dilute 1+14 for greater control and then use it as a single-session developer.

Again, nothing but direct observations of results obtained in my home darkroom. No strict controls of any kind.

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Well, that is still a valuable feedback to me and it's also what counts ultimately. I do a lot of numerical calculations and chemical measurements in the early phase of developer development but in the last phases I'm making more fine changes by looking at test prints... Just like what vintners and whiskey distillers do.

Thanks for your comments again.