15

Conventional wisdom says yes, you should use a stop bath. The stop bath is a very weak acid (similar to white (distilled) vinegar) and is used to neutralise the developing agent. This guarantees two things: You can be sure that you won't have any additional development happening after the developer bath. You won't contaminate your fix with developing agent. ...


8

I think it was the EktaSpace that was invented to hold all colors of films. Since silver halide color papers are still used as media for printing from digital, there are also color profiles of photographic papers floating around the Internet. See https://www.drycreekphoto.com/icc/ for examples. These should give you some idea. As you can imagine, ...


6

One way to check is to take a small piece of undeveloped film (you can use a bit of film leader) and put it in the suspect fixer (this can be done with the lights on). It should turn transparent in less than 1/2 the recommended fixing time. To turn it on it's head- the fixing time should be at least twice the clearing time (some say 3 times the clearing time)...


6

Cold reduces reciprocity failure, and is used particularly for astrophotography. See http://en.wikipedia.org/wiki/Photographic_hypersensitization#cite_note-15. My own experience with Kodachrome (RIP) was that very cold weather reduced the blue-green cast of nighttime skies and cityscapes. Note that this could lead to frostbite, by the time the camera is ...


6

You can use the same container and mixing utensils and thermometer etc. for mixing. This is valid provided you take care to rinse well between solutions. Also, the items must not be porous (ceramic etc.). If you are in doubt regarding your ability to properly rinse, you can still proceed if containers and utensils are seasoned. To season, save small ...


5

The volume of the powder is so minor compared to a gallon as to not matter in practical cases. Don't worry about it. This small error in concentration is overshadowed by other sources of error: Your ability to measure the temperature and then chose the correct developing time. Keep in mind that temperature can change over the few minutes of the ...


5

SILVER use in photographic emulsions was a practical and cheaper concession after gold and platinum. While I have never used any of these materials, personally, I have seen prints of plates made from them on display at the George Eastman House in Rochester, New York. They may still be there. Platinotypes [sp?] had twice the greyscale of silver which seemed ...


5

It depends how far past the expiry it is, and how it's been stored. Different types of developers also degrade at different rates. Some developers will work just fine for years after their expiry date, others may be completely useless after a few months. The first noticeable difference would be in the development time. Old developer will take longer, so you ...


5

I foud this graphic on photo.net, in a thread discussing the same topic: I can't vouch for its veracity, but it looks reasonable. Both of the depicted films are a bit wider than AdobeRGB in the reds, but much shorter in green. But see the discussion on the next page, deeply saturatd greens require high densities and thus dark colours, which this chart doesn'...


5

Check the color of the fluid in the bottle. If it's dark or black, discard. If clear (amber OK) place the bottle of concentrate in a bowl of hot water from the kitchen sink. As the temperature elevates, shake periodically, as this will speed the re-dissolving of the crystals. Worried it's bad? Cut off a snip of the tongue for testing. Make a tiny volume of ...


5

R09 - or Agfa Rodinal - is a developer known for longevity. I have friends who use East German R09 (30 years or so old bottles) with great success. But it is long lived in more than one sense - it has been around for ever (since 1890'ies) and the patents that once covered it have long lapsed. Over the years there were several variants produced - some still ...


5

You are basically on the right track. If you have a powder mix, as is common for black and white developers, the different substances are not uniformly distributed, but depending on grain size, density and perhaps even grain shape. It may work, but in general, you can't divide such a powder mix and expect the ratio of the different substances to remain the ...


5

Photographic chemicals are generally robust however they will lose their effectiveness over time. Exactly how long will be their shelf life is a variable. Developers tend to have the shortest shelf life. This is because the developing agents are relatives of benzene which was initially synthesized from coal. These agents have an affinity for oxygen. They ...


5

The 30 seconds is "wet time". In other words, you pour in the stop bath (or dunk the film in), this stop bath solution for 30 seconds (time in this solution is not critical). This Adox stop is an indicator stop. In other words, this solution contains an indicator dye that changes the solution to blue (indigo) when exhausted. The rest of the story -- ...


4

The various chemical solutions of the photo process can be safely stored in glass or high density polyethylene (HDPE). Nalgene is a trade name for this material by Fisher Scientific. It is important to consider the lids and caps; they should also be resistant to these chemicals. Keep in mind that polyethylene bottles other than Nalgene are also acceptable. ...


4

I think using a bath tub for development is a bad idea. you won't be able to clean the bathtub perfectly, after some time you will have some stains in hard to clean areas as far as I know the particular benzene derivative contained in Rodinal is not known as carcinogen, but many similar chemicals are and I would not expose naked bodies of innocent people ...


4

The fix solution you seek is one of the most inexpensive chemicals of the black and white process. You can use most any fixer formulas. In other words, fixer for X-ray, fixer for film and paper. You might buy some from a local camera shop or photo studio. In any event, the stuff is benign. You be at ease, allowing your students to work with it. It has the ...


4

The problem with photo chemistry is that it changes and becomes unusable. The rate of change is best controlled by limiting the amount of exposure to air and warmth. Control the air by storing in the smallest bottle needed and making sure it has a good seal. Control for warmth by storing at room temp, or even better, in a fridge. I’d say that, yes, you ...


3

Film photography embraces the use of chemicals. For the most part, the chemicals we use are benign; otherwise the darkrooms of the world would be labeled as a hazardous workplace. Not to say there is absolutely no danger as the potential to mishandle chemicals is with us always. There are a plethora of developer formulas, all have advantages and ...


3

The first successful fixer is sodium thiosulfate. In the 60’s when ammonium thiosulfate became available it became the fixer of choice because it operated about twice as quick. Nowadays ammonium thiosulfate is the norm, however, either will work. Now color film and color paper use carefully selected organic dyes. These dyes blossom if the pH (acidity – ...


3

The capacity of the C-41 process as published by Kodak is 60 rolls of 35mm 24 exposure per gallon. This works out to about 12 rolls per liter. In other words, if the solution is fresh and you wish to process 100 rolls at the same time, the volume needed can be calculated as 100 ÷ 12 = 8.3 (8.3 liters). Under batch processing conditions, if you are not ...


3

Didymium gets its name from being composed of two of the lanthanide elements, praseodymium and neodymium. These are not particularly poisonous, and are quite safe bound into solid glass. B&H Photo-Video mentions that Tiffen and Lee sell these filters as "enhancing filters" and Singh-Ray calls them "intensifying filters". You might also try a sodium ...


3

Today those of us not in the color reproduction industry as a profession tend to talk and hear a lot more about certain color spaces that a particular imaging device can or cannot support than our counterparts heard before the digital imaging age. Saying an image device (such as a camera) supports a standardized color space means it is capable of producing ...


3

I am not sure if the following works for an actual answer because I figure that it will take an actual chemist or at least a professional photographer that has many years of experience to tell. But since this is too long for a comment, I decided to post it as an attempt to an answer. I tried googling for an answer to this question and the closest ...


3

Alkali earth metals have some photosensitivity. Not nearly as good as AgX, though. I'm assuming you realize that silver halide is not a single material, but refers to silver in combination with any of the halides: fluoride, chloride, bromide, iodide. Usually alternative processes use various combinations of these.


3

Developers contain several chemicals that are sensitive to oxygen. The chances are that they deteriorated a bit. D76 is not so expensive or not so special and I would recommend to get a new one. If you decide to use it anyways, check the color of the solution after you mix it together. It should be pretty much colorless. Any (likely brown) coloration is a ...


3

The unmixed powders, such as XTOL or D-76, in their original sealed packaging can be expected to last several years. However, with age does come increased risks of issues. If the powder remains as fine grains and pours smoothly, then that is a good sign that there were no issues in storage. If it is clumpy, has uneven texture or colours, then treat with ...


3

Adding a top coat of hot liquid paraffin is in the "how to do it books" for storage of photo chemicals. I did this 50+ years ago in my home darkroom in the water heater closet. Better is adding clean marbles or using plastic storage bottles and squeezing the air out. I have used nitrogen filled bottles. I have used nitrogen filled storage tanks. I have used ...


3

The specific difference between the Cinestill 2-bath developer kit and the Tetenal 3-bath developer kit is that Cinestill leaves out the final stabilizer bath, or more precisely label it as 'optional'. They claim in their data sheet that modern C41 films contain embedded stabilizer chemicals, which are released during the first two baths, so that a separate ...


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