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#12
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#13
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Jobo & Pre Rinse?
Keith Tapscott. wrote:
: Frank Pittel;929863 Wrote: : I got a recipe for xtol and the only thing that was a challenge to get : was the "DTPA" and I'm convinced that EDTA would work just as well. I : got : the DTPA from artcraft chemical and dimezone-s from the Photographers : Formulary. : : : ------------------- : Keep working dumbo needs the money : I may try the formula for the Xtol patent, but I will use metol at 2 : grams per litre in place of dimezone-s. Is there a reason for using metol instead of dimezone-s? My understanding is that dimezone-s is a form of phenidone. The next time I mix up xtol I'm going to try using edta instead of the dtpa. The dtpa in the quantities I'm ever going to use the stuff at is expensive. Of course I bought 100gm of the stuff and the recipe I have uses 1gm per liter of stock and I've got a supply of the stuff that will lat me for years at my current rate of use! :-) -- ------------------- Keep working dumbo needs the money |
#14
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Jobo & Pre Rinse?
Frank Pittel wrote:
: Keith Tapscott. wrote: : : Frank Pittel;929863 Wrote: : : I got a recipe for xtol and the only thing that was a challenge to get : : was the "DTPA" and I'm convinced that EDTA would work just as well. I : : got : : the DTPA from artcraft chemical and dimezone-s from the Photographers : : Formulary. : : : : : : ------------------- : : Keep working dumbo needs the money : : I may try the formula for the Xtol patent, but I will use metol at 2 : : grams per litre in place of dimezone-s. : Is there a reason for using metol instead of dimezone-s? My understanding is : that dimezone-s is a form of phenidone. The next time I mix up xtol I'm going : to try using edta instead of the dtpa. The dtpa in the quantities I'm ever going : to use the stuff at is expensive. Of course I bought 100gm of the stuff and the recipe : I have uses 1gm per liter of stock and I've got a supply of the stuff that will : lat me for years at my current rate of use! :-) Minor correction. I bought 250gm of DTPA instead of 100gm. :-) -- ------------------- Keep working dumbo needs the money |
#15
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Jobo & Pre Rinse?
In article ,
Richard Knoppow wrote: There are two reasons Jobo reccomends a pre-soak. One is that it saturates the emulsion and contols the rate of uptake of the developer. That insures it is taken up evenly to eliminate blotching. The development is also slowed somewhat because the "induction time", that is, the time between immersing the film in the developer and the time the image begins to appear, is lengthened. Because of the very rapid agitation in the drum the development time is quite short compared to other non-machine methods so that increasing it a little also tends to insure uniformity. The second reason is to temper the tank. This is more necessary for color development done at elevated temperature so that the temperature of the developer is not suddenly changed when entering the tank. I strongly recommend *against* use of a pre-soak when developing color film in a Jobo. I think if you peruse the various web fora you will find a number of former Kodak chemists making the same recommendation-against. Many modern Kodak materials (at least) are manufactured in such a way that developer penetration into the emulsion is controlled by an "overcoat" of non-sensitized material. Among other issues, pre-soaking defeats this, so that you are not developing the film as its designers intended and may not obtain the same curves they publish, even with the same developer at the same concentration. A nuisance with black and white materials, but a more serious issue with color ones. Kodak recommends either the use of temperature controlled hot air blown into the tank instead of a presoak (I do not know what kind of rotary-tube machine can do this) or a longer preheat with the tank in the water bath but no liquid in the tank. I use the latter method and have always had good results even with processes with very short times for some steps such as C-41RA. -- Thor Lancelot Simon "All of my opinions are consistent, but I cannot present them all at once." -Jean-Jacques Rousseau, On The Social Contract |
#16
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Quote:
I also find Metol much easier to weigh than Phenidone. You are correct that Dimezone-S is a Phenidone derivative. EDTA (fe) might work with the developer, but why not just stick with the DTPA now that you have already bought some? For Xtol-M (Metol), I would start with the times given for D-76 and ID-11. |
#17
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EDTA (fe) should have been written as EDTA (NA-FE), oops.
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#18
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Jobo & Pre Rinse?
Keith Tapscott. wrote:
: EDTA (fe) should have been written as EDTA (NA-FE), oops. I knew what you meant. :-) -- ------------------- Keep working dumbo needs the money |
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