How many ingredients?
This article about Kodak Dektol mentions how commercially packaged developers are far more complex than the basic formulas such as D-72 of which Dektol is based on.
Some of the extra components are mentioned in the article as being so minute, that special weighing equipment is required. See the paragraph headed FORMULA TREND.
I wonder how many components are added to such developers beside a sequestering agent?
Yes, the presence of a sequestering agent was found out the hard way. I have hard water (Philadelphia) and I got cloudiness for my trouble in mixing up some D-72. Adding the sequestering agent AFTER the fact does no good. You must START with good water if you wish to mix from scratch, either distilled or properly treated with a sequestering agent (like sodium tetraphosphate or sodium hexametaphosphate or others). THAT will (excuse my lack of chemistry knowledge) keep the calcium from interacting with the carbonate by keeping it in a 'prison' of sorts by binding it in a ring! (CHELATING).
But, in addition, Kodak says that the capacity of Dektol is slightly greater than is D-72 so the developer component must be enhanced. I do not know what else they have done because the oxidation propensity is not, in my opinion, improved with Dektol. - David Lyga
I keep sodium hexametaphosphate (formerly called CALGON) in my darkroom cupboard and recommend it for most home mixed developers. I'm not sure if it will be suitable for pyro devs.
I have been involved in formulating many of the recent Kodak black-and-white film developers (T-MAX, Duraflo, Technidol) so I offer these comments:
Commercially produced branded chemicals are different from the generic published formulas for several reasons. The published formulas are made available to help those that wish to to mix their own processing chemicals. The materials listed need to be widely available. The manufacturer may have an unique in-house component that works better than the generally available material so the in-house material is used.
The goal of the commercial and published formulas is to provide SIMILAR photographic results. Identical is a lofty goal. Identical results are not achieved in photographic products. With careful examination there are ALWAYS differences.
Also, the performance requirements placed on a commercial product are stricter than mixed-at-home product i.e. storage tolerance, tolerance to a variety of water contaminates, manufacturing requirements, etc.
A manufacturer may have a proprietary ingredient that will improve the product's photographic performance. This is the case with most if not all Kodak chemicals as well as Ilford's ID11 Plus.
Manufacturer's may also include a trace material to aid in identifying the source of the chemical product. There are instances where counterfeit chemicals have been detected and also cases where there are complaints on chemicals when the chemicals were actually made by someone else.
Component measuring isn't an issue for photochemicals. It is a greater issue in film emulsion manufacturing where accuracy is even stricter. To deal with parts per billion accuracy there are two totally separate approaches that are both needed. Purity of the components and addition of tiny amounts.
There are some components in film at very low levels that help performance. If the level is increased it will totally destroy the film's performance. Mercury is well known for this. It is immaterial whether the Hg comes from a measured addition or is an unintended contaminate in a raw material. The most accurate way to deal with this is to use nearly Hg free materials and then add exactly how much you want to be present.
This is easier said than done. Mercury and other contaminants to AgX are present in many required components so it has to be removed. In "the old days", (1970's) some known contaminates were required to be present in the raw materials. This meant that gelatin from animals that were fed specific food were required to make a specific product.
For addition there are multiple chemical preparation and addition workstations. The workstation that is used depends on the handling requirement i.e. worker safety, contaminate characteristics, and of course material quantity. For parts per million additions there is a separate weighing and addition station that is used to precisely and accurately makes additions.
This is described in: makingKODAKfilm.com
A calcium sequestering agent is needed for carbonate developers and also for developers that contain a large amount of sodium sulfite. In the first case calcium carbonate may precipitate and in the second case calcium sulfite.
While borates cannot be used with catechol and pyrogallol, pyrophosphates are ok.
Don't worry about any of the extra ingredients in Dektol and other commercial versions of developers. Kodak is not hiding a magical ingredient from the user. Some "extras" are used to achieve a stable powder mix, others to help the stabilility of the mixed developer, etc. For example, Microdol contained an antisludging agent.
Dektol evolved from a 2 part developer packaged in cans or jars. to a 1 part developer packaged in a foil packet. To do this it was necessary to move from D-72 to Dektol in formulation. The developer had to survive mixing in all sorts of water except sea water.
The sequestrant was one of the first additions and after that it was necessary to learn how to mix HQ and Metol with the other ingredients and keep them from decomposing. This is a long hard process that involves essentially encapsulation or isolation of the various ingredients to prevent interaction. The developer is also made up under an inert atmosphere.
I have posted more details on this in a similar thread. This commentary keeps coming up. Everyone is curious. Let it be nted that D72 gives results that are identical to Dektol in contrast, Dmiin, Dmax, and speed. Capacity and longevity are another matter, and that is why I tested Liquidol against Dektol and not against D72.
Gordon Hutchins chose metaborate for his PMK formula, so I guess he went against that advice.
Originally Posted by Gerald C Koch
The extra ingredients in packaged developers don't worry me, I was just curious to know more about them. Thanks Gerald. :)
I have not tried Liquidol, does it mirror Dektol/D-72?
Originally Posted by Photo Engineer
There is an example posted here, but basically Liquidol has about 2x - 4x the capacity and tray life compared to Dektol. I have gotten usable results after 120 hours keeping in an open tray. Dektol is virtually dead by then. OTOH, I find that it does not do well at high temperatures. It is foggier than Dektol. That can be corrected by use of Bromide or BTAZ.
I forgot to add in the previous post that Dektol differs from D-72 in about 3 ingredients. One is the "stabilser" to permit the developing agents to be mixed with the other ingredients, the other is the sequestering agent(s), and the third is a "buffer" to improve tray and tank life. You might also say that the inert gas used to mix and pack it is an ingredient as well. I guess you could also say that about the mixing or blending method itself is unique.
Tossing a bit of Glycin into D-72 extends its life quite a bit. A bit like Ansco 130. I've never read any explanation for the action.
D-72 also lasts longer at 1:1 and if it has extra S. Carbonate added to it.
I wonder what a combination of ascorbate and Glycin would do? I feel an experiment coming on...