Rodinal
Rodinal is the trade name of a developer for black and white films based on p-aminophenol, developed by Agfa and now manufactured by ADOX .
history
Rodinal was patented on January 27, 1891. The main innovation was that the film developer was no longer supplied as a powder, but as a liquid concentrate that only had to be diluted in the correct ratio. The invention of the Agfa employee Momme Andresen established the photographic division of the Agfa company and is the longest ever product for photography on the market . Rodinal is even listed with an entry in the Guinness Book of Records .
After the separation of Agfa into ORWO (GDR) and Agfa (Leverkusen), Rodinal was sold in the GDR as ORWO R09 (recipe number Rodinal number 9). Agfa Leverkusen has improved the recipe several times and most recently produced it in Vaihingen (Enz). When Agfa went bankrupt in 2004, ADOX took over the production of the Agfa formulation . ADOX now also owns the naming rights to Rodinal.
Components
The main components of the product available today contain the following chemicals:
- p-aminophenol as a developing substance
- Potassium hydroxide to adjust the pH value
- Potassium sulfite
- Na4EDTA
- Potassium bromide
Recipe
Rodinal's original recipe was published in 1892 and is included in the patent. The recipe has been improved several times. When the Allies looted the Agfa plant in Wolfen in 1945, the recipe that was currently used at the time fell into their hands. In the report of the Combined Intelligence Objectives Sub-Committee , it has since been read:
Wasser 75 ml p-Aminophenol 5,5 g Kaliumsulfit sicc. 4 g Kaliumhydroxid 4 g Kaliumbromid 1 g Na4EDTA 2 g Wasser auf 100 ml
Today, because of the better properties, one would rather use free p-aminophenol and no -hydrochloride. It is best to first dissolve the potassium hydroxide in 4 ml of water and then add it. Only then, in the now alkaline environment, does the p-aminophenol dissolve in it.
use
Rodinal is supplied as a concentrate and must be diluted before use, with dilutions in the ratio 1 + 25 (1 part Rodinal plus 25 parts water), 1 + 50 and 1 + 100 being common, with higher dilutions leading to a slower development process, but increase the apparent sharpness of the film. The edge effect occurs in a wide range regardless of the frequency of the developer movement. Stand development and rotation development, however, give poorer results. Dilutions of 1 + 100, 1 + 200 or even more are used for the stand development, i.e. without any tilting or moving. The diluted solution cannot be reused after use and should be disposed of in the pollutants.
The development process can be accelerated by increasing the temperature, and the contrast of the film can be controlled by adjusting the time . However, a higher temperature is not advisable, as otherwise the film grain will be accentuated even more.
The following tables show the development times for Agfa films in Rodinal with a 30 second tilting rhythm. In the first minute must be moved continuously. The development is also reflected in the use of speed: if you want to develop an Agfa APX100 in Rodinal 1 + 25, you can use a slightly higher speed of 125 ASA (instead of 100 ASA) when exposing the film.
Dilution 1 + 25 at 20 ° C
| Movie | gamma | time | ISO |
|---|---|---|---|
| Agfa APX25 | 0.65 | 6 min | 20/14 ° |
| Agfa APX100 | 0.65 | 9 min | 125/22 ° |
| Agfa APX400 old | 0.65 | 7 min | 400/27 ° |
| Agfa APX400 new | 0.65 | 10 min | 320/26 ° |
Dilution 1 + 50 at 20 ° C
| Movie | gamma | time | ISO |
|---|---|---|---|
| Agfa APX25 | 0.65 | 10 min | 25/15 ° |
| Agfa APX100 | 0.65 | 17 min | 160/23 ° |
| Agfa APX400 old | 0.65 | 11 min | 500/28 ° |
| Agfa APX400 new | 0.65 | 30 min | 320/26 ° |
Agfa recommends using a minimum of 10 ml of Rodinal for the development of each film (135 film or 120 roll film). With a dilution of 1 + 50, 510 ml of working solution must be prepared. Contrary to the opinion of many photographers that 5 ml per film is sufficient, one is always on the safe side with the information from Agfa. A dilution of 4.7 ml Rodinal and 235 ml water is often used, as the filling volume of a Jobo can is exactly 240 ml for a 35mm film .
Edge effect
At the edges , i.e. H. At the transitions between light and dark image areas, the developer is used up more quickly in the latent dark areas in the negative than in the light areas. The used developer inhibits the development at the edge and thus ensures a fine, light line that intensifies the impression of sharpness.
One way to maximize the edge effect could be to dilute Rodinal a lot and let the film stand for a long time. A similar effect is used today in image processing to improve the subjective impression of sharpness of a photo.
durability
According to the manufacturer Agfa, the Rodinal working solution should be used up quickly. The developer concentrate oxidizes after a very short time in the air and noticeably takes on a brownish color. Fresh rodinal is clear and colorless. The storage container with the concentrate should therefore always be filled with a protective gas ( propane / butane , heavier than air) after removal . It is also possible to add glass balls until the container is full to make up for the loss.
In practice, however, Rodinal in concentrated form has proven to be a particularly unproblematic developer in terms of durability. Even rodinal that is already deep brown is still working perfectly and completely normally as a developer. There are reports that an opened bottle of Rodinal was found when a school's photo lab was closed. The concentrate was deep brown in color and was in a brown glass bottle with a yellowed paper label, which has not been sold for several decades. This developer immediately delivered the same results as fresh rodinal.
At the bottom of the bottle of concentrate always are a few crystals . However, this has no significance for the durability or effectiveness of the developer , but they should not be added to the developer container. From filter is easy with a coffee filter possible.
Derivatives
In addition to the various Rodinal derivatives that are offered by different manufacturers, there is the option of preparing a developer based on Rodinal yourself. The simplest version of the so-called Parodinal consists of water, paracetamol tablets ( acetaminophen ), sodium sulfite and sodium hydroxide . In this way, a developer can be produced in a simple manner from cheap and widely available ingredients, which in its characteristics comes very close to Rodinal. In addition, in contrast to p-aminophenol, paracetamol is much less dangerous for the environment and your own health.
Web links
- Story of Agfa Rodinal ( Memento from February 11, 2002 in the Internet Archive )
- Rodinal self-approach
- Parodinal self-approach
- ADOX Rodinal
Individual evidence
- ^ History of Rodinal. Retrieved August 5, 2019 .