Metol+Phenidon .... superadditive?!
Well known that metol isn't superadditive with phenidon. But I found patent US 5998110. Author research some types developer (PQ, PC, PM(etol), PG(lycin)) at pH ~10 and claim that PM combination is superadditive and have same speed as PQ/PC with near same ratio of phenidone to 2nd developer agent
Also in this patent found interesting research of changing pH of developer during oxidation (see example 3, table 4). Initial pH of all tested developer is same - 10.27. For 72 hours of oxidation PQ change pH to 12.27, PC - to 8.82 and PM to 11.5
Ilford did publish a Metol/Phenidone/Hydroquinone developer in s Patent and Crawley mixed all 3 but I've never seen any benefits of using both Metol & Phenidone.
Last edited by Ian Grant; 09-14-2011 at 03:59 PM. Click to view previous post history.
Crawley,BJP Dec16 1960 explained why metol-phenidone-hydroquinone gives more speed than phenidone-hydroquinone:
"In FX-4 the metol-phenidone-hydroquinone combination is used.This reduces overall contrast and allows the shadows to increase in contrast more than (phenidone-hydroquinone) FX-3 by the time normal gammas are reached...."
I wonder if speed increase may sometimes incorrectly be attributed to superadditivity when it is in fact due to the mechanism Crawley describes.
The same question arises in respect of your attributing properties of phenidone -glycin to superadditivity in your metol glycin developer thread.Crawley's simple explanation may suffice.
pls read patent before reply )) we talk about developer with two component. not 3, 4, 5, or many ))
also additivity of phenidon+glycin found in Anchell "Cookbook"
Generally, the combinations of developing agents showing superadditivity consist of one developing agent from the dihydroxybenzene type (hydroquinone) and one developing agent 3J from either the aminophenol type or the 3-pyrazolidone type. There is a case reported at page 29 of Mason in which one of the developing agent is not of the dihydroxybenzene type, that is the case of the Phenidone/Glycin system
which, however, has proved of poor utility.
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also superadditivity phenid+glycin described in patent US3778267 - modified POTA developer with glycin
Well, a patent doesn't have to be technically correct to be issued, exactly. It is supposed to be "operable", but patent offices do not ordinarily enforce a "must prove operability" requirement. The history of patents for perpetual-motion machines is interesting in this regard (and eventually led the USPTO to establish a specific prohibition on patents for that particular impossibility, since they were so numerous as to be a nuisance to the office).
On the other hand, the inventor was apparently employed by Ferrania and involved in multiple other developer patents, so I'd expect the filing not to be complete nonsense. (On the third hand, I've filed some applications for things that might lead a reader with the benefit of hindsight to say "What the @#(*&@ was this idiot thinking?")
Claims 2 and 4 do seem unambiguously to imply that the inventor thinks metol and phenidone are superadditive. I guess either the inventor is wrong, or everyone else is?
Finally, it really worries me that the only patent with a reference to this one is a "Boar cart for insemination of sows"!
San Diego, CA, USA
The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
-The Little Technical Library, _Developing, Printing, And Enlarging_
I have a photographic science background and worked with these two compounds extensively on some special mil spec developers back in the 1980s. We had some very interesting formulas for special one-off Kodak SO (special order) type films that ran about $600 for 15gallons because each batch was hand weighed out back in Rochester and nobody knew exactly what was in it but came in special. It oxidized in one week and we threw it out!!
Ilford invented Phenidone.
Phenidone is generally accepted as a synthetic substitute for Metol and can be interchanged as long as you know the formula. If memory serves me right Phenidone was about 10x the power of metol, so 10 grams of Metol = 1 gram of Phenidone.
It's also hypoallergenic compared to Metol so if you get a reaction to Metol based developers try Phenidone variants. Developers with Phenidone in them have a very sweet smell and have a pink tint to them initially.
I cant comprehend what you would gain by using both that you couldn't accomplish with just using more Phenidone or a lot more Metol in the formula. The result is the low contrast range of course, and you could use a variety techniques to accomplish that.
(sorry for the hi-jack, could not help it)
"The history of patents for perpetual-motion machines is interesting in this regard (and eventually led the USPTO to establish a specific prohibition on patents for that particular impossibility, since they were so numerous as to be a nuisance to the office)."
a perpetual-motion machine produces more power than it consumes!
under that definition at least 2 have been patented and produced and released to the general public
1) Tesla's bladeless turbine (1914?) by itself it's a marvel but when a second unit is attached to and driven by the first it acts as a 'super-charger' producing much more power than it consumes.
2) Ford's ceramic catalytic converter, the orginal 'cat' was patented in the 1950's, Ford made it easier to produce in the 1970's. It produces quite a lot of energy (power) and consumes almost nothing but fresh air.
Combine the two and watch what happens.
may be we back to photo? )) from patent US5998110:
at pH 10.7:
2.25g/l phenidon + 20g/l hydroquinone reach Dmax 3.45
2.25g/l phenidon + 30g/l metol reach same Dmax 3.45
30g/l metol without phenidon have Dmax less than 1
author can't test developer with only phenidon, but as well known phenidon as single deveping agent produce very low gamma and Dmax (see POTA and modification)
so if phenidon+metol isn't superadditive Dmax(phenidon+metol)=Dmax(metol)+Dmax(phenidon) < 2, but we have Dmax(phenidon+metol)=3.45!
I think that this result need more arguments for refute than like "this is bull$%^#" or "perpetual motion"
Last edited by Relayer; 09-15-2011 at 04:50 AM. Click to view previous post history.