The chemical used in photography?
What is the chemical used to make photographs permanent?
- photogLv 79 years agoFavorite Answer
There are a number of different chemicals dependent on the type of film, and the materials used in developing and printing.
There are the chemicals used to make the film, the developers, the fixer and the stop agents.
The different chemicals themselves used in developing and printing are also mixed in different proportions depending on manufacture/type of film and effects.
- Camera GuyLv 69 years ago
In BW paper developing you usually have 3 separate chemicals.
Once exposed from the light of a enlarger, the developer changes the exposed silver that is in the enlarging paper to black, or shades of gray depending on how much light the paper received. The standard developing time is set to 2 minutes at around 68 to 72 degrees. This can usually be done with what is called a safe light on, usually red, some deep orange and you can watch the process happen in the tray as it develops. You rock the tray or gently move the paper until the end of 1 minute and 45 seconds, then you lift the print out of the developer and let it drain for the remaining 15 seconds and slip it evenly but quickly into tray # 2..
The Stop Bath - is a mild acid smelling liquid, somewhat like vinegar. It is Acetic Acid. It's one and only purpose is to halt or stop the developing process like, right now..! Stop it dead in it's tracks. The reason is, you don't want your image to continue developing after the set time or it can look different, over developed, and NOT what you want. The stop bath step is about 1 minute long.. but can be 5 minutes or so if needed or wanted because you are busy elsewhere (potty..?)..
At this step the paper is still sensitive to "white light" and will fog and be ruined if lights are turned on. The last chemical step allows the print to finally see "daylight"...
The 3rd step is the Fixer, and this too is a mild acid and between it and the stop bath they give a darkroom a smell that many have come to actually love and be "addicted" to.. Anyhow, the Fixers acid content dissolves all the un-used light sensitive silver still in the BW print, leaving all the exposed silver, the black and gray stuff, the image, alone. It also hardens the emulation somewhat to make it more durable as well. The fix process is timed at 5 minutes and while 6, 8 or 10 is not harmful, it's also not advised.. It IS a mild acid and can bleach the print some what.
After the print has been in the fixer for at least 2 or 3 minutes you could turn the white lights on now, if you wished. After the 5 minutes you remove the print, draining off the excess fixer into the tray and then slip the print into a tank of fresh ever changing running water for 15 to 30 minutes to make sure you wash ALL the fixer off. There IS a 4th chemical step you could use to reduce rinse time and this is a chemical step that neutralizes the acid in the fixer thus allowing a shorter rinse time, saving water.
If the fixer is not fully removed there is a very good chance your prints WILL yellow with age and if on real paper, fiber base stock, the paper can crumble and acid rot like old newspaper.
There are and can be a gazillion variations to this, but this is basically it..
- david fLv 79 years ago
While the other answers have outlined the chemistry of traditional photography pretty well, the chemical which does what you ask, that is, making traditional photographic prints permanent, is water. H two O. It is used to wash away the residues of all the other chemicals after the print has been developed and fixed. Without it, the print will not be permanent. It will rapidly discolour or fade, or both.
- CynthiaLv 45 years ago
The emulsion (coating) on black and white film and photo paper is made largely of silver salts - sometimes called silver halides because the compounds are made of silver plus a halogen. Silver Chloride and Silver Bromide are silver salts. When light hits the emulsion, it starts a chemical reaction whereby the halogen separates from the silver, leaving the silver behind - which appears black. If you leave the film or photo paper in a bright light for a long time, it will eventually turn dark, but generally a developer is used to accelerate the reaction. After the film is developed, the chemical reactions are temporarily stopped with an acedic acid solution or plain water. - A fixer of sodium thiosulfate is then used to stop the chemical reactions completely. Just as table salt (Sodium Chloride) is soluble in water, Silver Salts are soluble in the fixer.- but the black silver is not. As a final step, the film or paper is washed with water to remove the chemicals, leaving only the silver behind.
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- loLv 69 years ago