Could you explain how chemicals and processing work?

[Frostice100]

Hello, i am new in analogue photography and this is my first post on this site. I am fairly young and i wasn't during the film era.
I started shooting film some months ago. Mostly Kodak ColourPlus 200 and FujiChrome 200 (cheap and easy to find, just for starters, since i live in a small town and all the labs here have only those two to sell). I have experimented with afga APX 400 and still have many other films i want to try.
My question though has to do with chemicals,I've decided that i'd like to process my own film (probably B&W mostly).To my knowledge all i need is a developer,fixer,use water for stop bath and of course a tank. Yet for colour film processing all I find is kits. Why is that? Why do they have kits with all the chemicals inside. Isn't there a general way of processing colour film. Everyone seems to use a kit. Also why does colour need a certain temperature also?
Could you explain how developing works, why we use those chemicals and why so many differences.I know in general what each chemical does but what happens in the film in a more technical level, why do we use what we use and how can i learn?
Thank you for your time and patience

 

[Mick Fagan]

Firstly, welcome to the forum.

B&W film in simple terms is one layer of emulsion, you only need to develop one layer, fix it, then hang it up to dry after washing.

Colour negative, which is what produces colour prints, has a minimum of three layers, with some having four layers. Each colour has it's own layer and the developer and the process has been designed to process each layer at the same time, even though each layer is treated a bit differently as one is on top, one is below that and maybe another two layers under the second layer.

Colour developing requires precise timing of the process, as well as precise temperature to get the ultimate correct negative. The chemistry for colour film requires very precise measurements and mixing to work correctly; colour processing kits mostly eliminate possible mistakes by people. That is the main reason for colour processing kits. The other main reason for colour processing kits is sourcing the chemicals to mix up the developer, bleach and fix in a package that can be delivered to different countries around the world.

In a nutshell, B&W developing is like keeping a single cylinder moped with one or two gears running, compared to a big diesel automobile with an automatic gearbox. You can make many mistakes with the moped and it will still run, but make sometimes only a tiny mistake with the big automobile and it will probably stop running.

Hope this helps.

Mick.

 

[Frostice100]

Colour developing requires precise timing of the process, as well as precise temperature to get the ultimate correct negative. The chemistry for colour film requires very precise measurements and mixing to work correctly; colour processing kits mostly eliminate possible mistakes by people. That is the main reason for colour processing kits. The other main reason for colour processing kits is sourcing the chemicals to mix up the developer, bleach and fix in a package that can be delivered to different countries around the world.
Mick.

Thanks Mick, glad to be here and thanks for the answer
Could you also tell me what's the difference between all those kinds of developers,fixers etc. and why people use more that the 2-3 basic chemicals?

 

[removed account4]

hi frostice100
its kind of a complicated process to be honest ..
text books have been written on the subject.
https://www.photrio.com/forum/forums/b-w-film-paper-chemistry.85/
https://www.photrio.com/forum/forums/color-film-paper-and-chemistry.86/
look for posts written by "photo engineer" he's a retired kodak photo chemist
and he explains pretty much everything you have an interest in knowing
as for why are there so many different kinds of developers &c..
that's like asking why there are different kinds of cars or bicycles ..
some developers are high or low contrast, some are for movie film, or negative film
some are using old chemical formulas some are new tech .. but they all pretty much
do the same thing .. they make the invisible latent image, visible.
the fixers are all pretty much the same .. either the original "hypo" ( sodium thiosulfate )
or the higher capacity faster working ammonium thiosulfate ( speed fixer )
have fun!

 

[Mr Bill]

Yet for colour film processing all I find is kits. Why is that? Why do they have kits with all the chemicals inside. Isn't there a general way of processing colour film. Everyone seems to use a kit. Also why does colour need a certain temperature also?

Hi, mostly color processes were not designed for hobbyists. The big users have always been photofinishers, and they don't use their chemicals in the same way that hobbyists usually do. A photofinisher mixes up their chemicals one time to start up a large machine, and thereafter only add relatively small quantities of "replenishers" to keep the machine "in spec." (A replenisher is much like an extra strength version of each chemical, but mostly too strong to use "as is.") Anyway, the chemical suppliers you are looking at are mostly specialized in supplying small-scale hobbyists who are best served by a ready-to-use kit. So that's probably what you're seeing.

There really is no "general way" of processing color. As Mick indicated, there is a fine balancing act going on, which is mainly only successful when following the specs set out by the process designer, generally Eastman Kodak - see process C-41 (film) and process RA-4 (paper). The specs for using these are given in the appropriate "Z" manuals for these, which can be found online.

When processed according to the specs, color films should be able to be optically printed (meaning with an enlarger) onto the appropriate color paper without too many problems. But if the film is NOT processed "just right," there will almost certainly be some problems with the prints - mainly some colors will not stay the same from shadows into highlights; it's called a "color crossover."

If you look through this site, you'll see that some people have done color film processing at different temperatures and seem satisfied; about all I can say to that is that they are most likely not too finicky about the color. OR they just scan the film, whereby nearly anything is correctable, depending on your skill.

 

[Mr Bill]

I know in general what each chemical does but what happens in the film in a more technical level, why do we use what we use and how can i learn?

There is an older book, originally from the late 1950s, I think, by George Eaton of Kodak, which is, I think, about as good an introductory book to photo chemistry as there is.

I don't know how readable you'll find it, but you can see it online here (developers start on Page 35) - https://archive.org/stream/photchem#page/n36/mode/1up

 

[Sirius Glass]

Welcome to APUG Photrio.

Start with XTOL for black & white development. It is very forgiving, just make sure the chemical bottle seals out the air. This is also why I use XTOL.

 

[MattKing]

Thanks Mick, glad to be here and thanks for the answer
Could you also tell me what's the difference between all those kinds of developers,fixers etc. and why people use more that the 2-3 basic chemicals?

Welcome to Photrio.
If you are asking about black and white processing, there are a couple of additional chemicals that have practical advantages.
A stop bath is a good idea because it is better at stopping development, and it extends the life of the fixer that follows it.
Film needs to be fully and completely washed. There are wash-aid chemicals like Kodak Hypo Clearing Agent that speed wash times and ensure complete washing.
And some sort of wetting agent like Kodak Photo Flo helps you avoid drying marks that appear when film doesn't dry evenly.

As for the differences between the types available, different developers give slightly different results. They also offer different advantages, such as economy, long life, capacity, ease of preparation. Sort of like different cars that appeal in different ways.

Stop baths come in two different general types - acetic acid based and citric acid based - and mostly can be used interchangeably. The citric acid versions smell less.
Fixers come in two different general types - rapid fixer (ammonium thiosulfate based) and regular fixer (sodium thiosulfate based and formerly known as "hypo"). The rapid fixers are faster and better with some films, but are only sold as liquids. The regular fixer can be bought as a powder.

Many of the chemicals from many of the manufacturers can be used interchangeably. It often makes sense to make purchasing decisions based on practicalities like local availability, expense, convenient packaging.

 

[Frostice100]

hi frostice100
its kind of a complicated process to be honest ..
text books have been written on the subject.
https://www.photrio.com/forum/forums/b-w-film-paper-chemistry.85/
https://www.photrio.com/forum/forums/color-film-paper-and-chemistry.86/
look for posts written by "photo engineer" he's a retired kodak photo chemist
and he explains pretty much everything you have an interest in knowing
as for why are there so many different kinds of developers &c..
that's like asking why there are different kinds of cars or bicycles ..
some developers are high or low contrast, some are for movie film, or negative film
some are using old chemical formulas some are new tech .. but they all pretty much
do the same thing .. they make the invisible latent image, visible.
the fixers are all pretty much the same .. either the original "hypo" ( sodium thiosulfate )
or the higher capacity faster working ammonium thiosulfate ( speed fixer )
have fun!

Thanks, appreciate the help. Indeed you're right 'photo engineer' seems rather experienced.Checked some of his posts.It's just all this chemistry and all these things that i simply can't get my mind around to understand.

 

[Frostice100]

There really is no "general way" of processing color. As Mick indicated, there is a fine balancing act going on, which is mainly only successful when following the specs set out by the process designer, generally Eastman Kodak - see process C-41 (film) and process RA-4 (paper). The specs for using these are given in the appropriate "Z" manuals for these, which can be found online.

Hi.Thanks for the answer.
What are the Z manuals? Are they manuals for developing colour and the chemicals you need to use to accomplish it?
Can you give me a link?
Thanks again

 

[Frostice100]

Welcome to APUG Photrio.

Start with XTOL for black & white development. It is very forgiving, just make sure the chemical bottle seals out the air. This is also why I use XTOL.

View attachment 189981​

Thanks for the recommendation
I just looked XTOL on google. Seems like a nice film. What if i push it. Will i get more grain?

 

[Frostice100]

Welcome to Photrio.
If you are asking about black and white processing, there are a couple of additional chemicals that have practical advantages.
A stop bath is a good idea because it is better at stopping development, and it extends the life of the fixer that follows it.
Film needs to be fully and completely washed. There are wash-aid chemicals like Kodak Hypo Clearing Agent that speed wash times and ensure complete washing.
And some sort of wetting agent like Kodak Photo Flo helps you avoid drying marks that appear when film doesn't dry evenly.

As for the differences between the types available, different developers give slightly different results. They also offer different advantages, such as economy, long life, capacity, ease of preparation. Sort of like different cars that appeal in different ways.

Stop baths come in two different general types - acetic acid based and citric acid based - and mostly can be used interchangeably. The citric acid versions smell less.
Fixers come in two different general types - rapid fixer (ammonium thiosulfate based) and regular fixer (sodium thiosulfate based and formerly known as "hypo"). The rapid fixers are faster and better with some films, but are only sold as liquids. The regular fixer can be bought as a powder.

Many of the chemicals from many of the manufacturers can be used interchangeably. It often makes sense to make purchasing decisions based on practicalities like local availability, expense, convenient packaging.

Thanks for the information

 

[removed account4]

Thanks, appreciate the help. Indeed you're right 'photo engineer' seems rather experienced.Checked some of his posts.It's just all this chemistry and all these things that i simply can't get my mind around to understand.

ive given up trying to understand, it makes it much easier in the end to just remember a few
things ... ( ignorance is bliss ! )
film in camera, expose to light, develop FIRST only expose to light again after you FIX ..
et voila !
works every time

best
john

 

[MattKing]

Is your question: "how do the chemicals and processing work?"
or is the question: "how do I use the chemicals and do the processing?"
The answer to the first question requires the sort of knowledge that chemists and engineers have.
The answer to the second question is something lots of us can help you with!

 

[Frostice100]

Glad to see i am not the only one. Thanks mate

 

[Frostice100]

Is your question: "how do the chemicals and processing work?"
or is the question: "how do I use the chemicals and do the processing?"
The answer to the first question requires the sort of knowledge that chemists and engineers have.
The answer to the second question is something lots of us can help you with!

I suppose it's the first one. I just want to understand why we use those chemicals into more depth, but the deeper you go, the more complicated it becomes.

 

[Prof_Pixel]

Using Google can help a lot. See for example https://en.wikipedia.org/wiki/Photographic_processing

 

[Mr Bill]

What are the Z manuals? Are they manuals for developing colour and the chemicals you need to use to accomplish it?
Can you give me a link?

Kodak's Z-131 manual is essentially the "operator's manual" for their C-41 process, which is the standard process for color negative film. It gives just about all the info an experienced lab operator would need to deal with that process, using Kodak chems, of course.

Hi, you'll find the Z manuals here - http://imaging.kodakalaris.com/professional-photographers/labs/chemistry

Most of the information is far beyond what you'll need, but everything you DO need (assuming Kodak branded chemicals) is most likely there. Commercial lab operators would most likely be using replenishers, so need starting rates for their configurations, etc. Most likely you would be making single-use batches, then throwing them away, so possibly you would only want the processing time and temperature range for each chemical. I dunno for sure how far you'll want to go.

If and when you get ready to take on color negs, make sure you understand the difference between what the trade calls a "tank solution" vs a "replenisher." If you have the option to buy a C-41 "developer" it is most likely a ready-made tank solution, exactly what you want for one-shot developing. If, instead, you buy a "developer replenisher," then you also need the appropriate "starter solution" to convert it into a "tank solution" (aka developer).

 

[Photo Engineer]

Perhaps I can help a bit here.

B&W processing forms a silver image (neg or pos) and you remove the left over silver halide. This requires a developer and a fix. A stop is useful and a wash is needed at the end.

For color, there are indeed 3 major layers but they are broken up into as many as 21 minor actors and they all have to move in the same way at the same time to make the proper color. To do this, you need a color developer and at the end, you must remove not only silver halide, but silver metal to make a clear image. For reversal, you also need a first developer. So, we have color develop, bleach and fix for films, but each chemical bath is affected by the previous bath, and therefore washes and even stop baths are used between them. At the end, you wash, but then you add a stabilizing agent to keep mold and fungus from attacking the images. You see, silver metal kills bugs so B&W films and prints are ok, but color has no left over silver and so a stabilizing agent is needed to kill those bugs.

The chemical reaction in B&W is simple... Developer + exposed silver halide gives you silver and oxidized developer. In color it is much the same, but then the oxidized developer goes on to react with a "coupler" which is incorporated in every color film. Each coupler is chosen to either make a dye or to correct color and there can be many many of them in any color product. Then, you have to remove the silver metal to make the dyes brighter, and to improve grain and sharpness.

How was this for you???

PE

 

[Mr Bill]

I suppose it's the first one. I just want to understand why we use those chemicals into more depth, but the deeper you go, the more complicated it becomes.

I'd again refer to the George Eaton book I referenced; it's a good foundation, assuming you can follow it. I haven't hardly been in it for thirty years or so, but on reviewing again, one of the best features is that he is so concise - you don't have to read through a lot of fluff to get the good stuff. And... he never steers you wrong, like so many books occasionally do. Anyway, with that foundation, you're ready for more in-depth literature. (This is on the assumption that you want to get a fairly thorough understanding and are ready to work for it.)

Fwiw, you really do not need this level of knowledge to do good work. The standard instructions from Kodak, or whoever, mostly suffice for that. And you can experiment with different developers, etc., and evaluate prints with only a "cookbook" level of knowledge. At some point, I guess it's whatever satisfies your intellectual curiosity.

 

[Frostice100]

Perhaps I can help a bit here.

B&W processing forms a silver image (neg or pos) and you remove the left over silver halide. This requires a developer and a fix. A stop is useful and a wash is needed at the end.

For color, there are indeed 3 major layers but they are broken up into as many as 21 minor actors and they all have to move in the same way at the same time to make the proper color. To do this, you need a color developer and at the end, you must remove not only silver halide, but silver metal to make a clear image. For reversal, you also need a first developer. So, we have color develop, bleach and fix for films, but each chemical bath is affected by the previous bath, and therefore washes and even stop baths are used between them. At the end, you wash, but then you add a stabilizing agent to keep mold and fungus from attacking the images. You see, silver metal kills bugs so B&W films and prints are ok, but color has no left over silver and so a stabilizing agent is needed to kill those bugs.

The chemical reaction in B&W is simple... Developer + exposed silver halide gives you silver and oxidized developer. In color it is much the same, but then the oxidized developer goes on to react with a "coupler" which is incorporated in every color film. Each coupler is chosen to either make a dye or to correct color and there can be many many of them in any color product. Then, you have to remove the silver metal to make the dyes brighter, and to improve grain and sharpness.

How was this for you???

PE

This was indeed a very expository post , and a very helpful one.So, for black and white, its a developer to show the image and a fixer to remove any traces of silver halide in? For colour though, you have a developer, a fixer and it would be great if you had a stop bath and a stabilizing agent. Could you explain more the use of each chemical in both black and white and colour. Also...what do you mean 'remove silver metal as well'.Whats the difference between silver halide and silver metal.
Thanks for the answer, got a better understanding!

 

[Frostice100]

I'd again refer to the George Eaton book I referenced; it's a good foundation, assuming you can follow it. I haven't hardly been in it for thirty years or so, but on reviewing again, one of the best features is that he is so concise - you don't have to read through a lot of fluff to get the good stuff. And... he never steers you wrong, like so many books occasionally do. Anyway, with that foundation, you're ready for more in-depth literature. (This is on the assumption that you want to get a fairly thorough understanding and are ready to work for it.)

Fwiw, you really do not need this level of knowledge to do good work. The standard instructions from Kodak, or whoever, mostly suffice for that. And you can experiment with different developers, etc., and evaluate prints with only a "cookbook" level of knowledge. At some point, I guess it's whatever satisfies your intellectual curiosity.

I skimmed through it a little. It actually seems very interesting and very easy to understand. I hadn't found an easier explanation such as this before. I'll certainly read it. Thanks for the book!

 

[RattyMouse]

Thanks for the recommendation
I just looked XTOL on google. Seems like a nice film. What if i push it. Will i get more grain?

XTOL requires you to make up a 5 liter batch. That's a huge volume unless you are going to process a lot of film quickly. I would never recommend XTOL to a beginner. Instead, Kodak HC-110 is a far more suitable choice. You can make up as much developer as you need it and it is very very cheap and easy. I would not get too hung up on which developer is best. They are 98% the same. It's not worth the stress trying to get that extra 2%.

 

[RattyMouse]

Perhaps I can help a bit here.

B&W processing forms a silver image (neg or pos) and you remove the left over silver halide. This requires a developer and a fix. A stop is useful and a wash is needed at the end.

For color, there are indeed 3 major layers but they are broken up into as many as 21 minor actors and they all have to move in the same way at the same time to make the proper color. To do this, you need a color developer and at the end, you must remove not only silver halide, but silver metal to make a clear image. For reversal, you also need a first developer. So, we have color develop, bleach and fix for films, but each chemical bath is affected by the previous bath, and therefore washes and even stop baths are used between them. At the end, you wash, but then you add a stabilizing agent to keep mold and fungus from attacking the images. You see, silver metal kills bugs so B&W films and prints are ok, but color has no left over silver and so a stabilizing agent is needed to kill those bugs.

The chemical reaction in B&W is simple... Developer + exposed silver halide gives you silver and oxidized developer. In color it is much the same, but then the oxidized developer goes on to react with a "coupler" which is incorporated in every color film. Each coupler is chosen to either make a dye or to correct color and there can be many many of them in any color product. Then, you have to remove the silver metal to make the dyes brighter, and to improve grain and sharpness.

How was this for you???

PE

PE, if all the silver is removed from color film, what is it that is making the visible grain?

 

[Mr Bill]

Whats the difference between silver halide and silver metal.

There is a group of chemical elements called halogens; they can combine with silver one-to-one, forming a so-called silver halide. The common ones in photography are mostly silver bromide and silver chloride. These do not behave as pure metals, but have their own characteristics. This situation is not unlike that of sodium chloride, aka table salt, which behaves completely differently from its components - sodium and chlorine.

Anyway, in film, silver bromide (mostly) crystals are specially treated to be sensitive to light. When the light-struck crystals are immersed in "developer," the chemical reaction converts them to metallic silver (with bromide ions being released into the developer solution). Note that developer does not (mostly) affect the silver halide crystals that were not exposed to light.

Now, an important thing about the "fixer" is that it can dissolve a silver halide, but not silver metal. So the metallic silver image is safe from the fixer, but all of the remaining silver halide, which could pose a problem for the permanence of the silver image, is dissolved and washed out of the film.

This is the basic gist of how a b&w image is developed and fixed. For a color image we also develop a silver image, but midway through the process we no longer need, nor want the silver image. We use a so-called "bleach" which also (typically) contains surplus bromide ions; the bleach "oxidizes" the metallic silver, which is then happy to take on bromide as a partner, becoming a silver halide again. And as already mentioned, the fixer will be able to dissolve the silver halide and remove it from the film.