Rodinal

Rodinal is the trade name of an exiled from the Agfa developer for black and white films on the basis of p -aminophenol.

History

Rodinal was patented on January 27, 1891. Main innovation was that the film developer was no longer supplied as a powder, but as a liquid concentrate that had to be diluted only in the right proportion. The invention of the Agfa- employee Momme Andresen founded the photographic division of Agfa and is the longest on the market for product photography at all. So Rodinal is even listed with an entry in the Guinness Book of World Records.

After the patent expires, the product was copied by other manufacturers and sold under different names, for example, by the company calbe which 09 produces a derivative according to the original original formula with their product R and markets. Rodinal itself was several times slightly modified over time by Agfa in the recipe. The recipe is known.

Components

Available today the product contains as main components the following chemicals:

• P- aminophenol as developing substance
• Potassium
• Na4EDTA
• Potassium bromide

Recipe

The original formula of Rodinal was kept secret from Agfa good reason more than 50 years. When in 1945 the Allies plundered the Agfa plant in Wolfen, they noticed the recipe in their hands. The report of the Combined Intelligence Objectives Sub-Committee, there have since read:

Water 75 ml p-aminophenol 5.5 g Potassium sicc. 4 g 4 g of potassium hydroxide 1 g of potassium bromide Na4EDTA 2 g Water to 100 ml Today would be used due to the improved properties rather free p -aminophenol and no hydrochloride. The potassium hydroxide is dissolved best first in 4 ml of water and put it on then. Only then, now in an alkaline medium, it dissolves the p- aminophenol.

Use

Rodinal is supplied as a concentrate and must be diluted before use, with 25 dilutions (1 part Rodinal plus 25 parts water), 1 50 and 1 100 are common, with higher dilutions result in a ratio of 1 to a slower development process, but increase the apparent sharpness of the film. The edge effect occurs over a wide range, regardless of a frequency of developer movement. However, state development and rotary developing arising worse results. Dilutions of 1 100, 1 200, or even more, are used for stand development, ie without any tilting or moving. The diluted solution can not be reused after use and pollutant disposal should be supplied.

By increasing the temperature of the development process can be accelerated, can be controlled by adjusting the time of the contrast of the film. This is not recommended from a higher temperature, as otherwise the film grain is accentuated even more.

The following tables show the development time for Agfa films in Rodinal are listed in 30 seconds Kipprhythmus. In the first minute must be continuously moved. The development is also reflected on the utilization of sensitivity: so who wants to develop an Agfa APX100 in Rodinal 1 25, a slightly higher sensitivity of 125 ASA ( instead of 100 ASA) in the exposure of the film to use.

Dilution 1 25 at 20 ° C

Dilution 1 50 at 20 ° C

Agfa recommends using Rodinal for the development of each film ( 135'er small picture or 120'er roll film ) a minimum quantity of 10 ml. At a dilution of 1 50 so therefore need to be set equal to 510 ml working solution. Contrary to the opinion of many photographers, that 5 ml per film is sufficient, one is with the details of Agfa but always on the safe side. Often a dilution of 4.7 ml of Rodinal and 235 ml of water is used as the charge of a Jobo - box corresponds exactly to 240 ml for a miniature film.

Edge effect

At the edges, that is, at the transitions between light and dark areas, the developer is consumed on the latent dark spots in the negative faster than the light. The used developer inhibits the development on the edge and thus provides for a fine bright line that reinforces the impression of sharpness. Some photographers swear by it, to let Rodinal greatly to dilute and available to the film for a long time, so that the edge effect is maximized.

Durability

Rodinal is to be used quickly by the manufacturer Agfa. The developer concentrate is oxidized after a very short time in the air and rapidly assumes a brownish color. Fresh Rodinal is clear and colorless. The storage container with the concentrate should always after removal of a protective gas (propane / butane, heavier than air) are filled.

In practice, however, Rodinal has proven to be particularly problematic developers when it comes to durability. Even already deep brown color tinged Rodinal works as a developer nor properly and completely normal. There are reports that an already opened bottle of Rodinal was found in the resolution of the photo lab of a school. The concentrate was deep brown in coloring ago and was in a similarly brown glass bottle with aged paper label, as it is no longer sold for several decades. This developer delivered right away the same results as fresh Rodinal.

At the bottom of the bottle of the concentrate are always a few crystals. However, this has no importance for the durability or effectiveness of the developer, but they should not be filled with in the developing tank. Filtering out is easily possible with a coffee filter.

Derivatives

Besides the various Rodinal derivatives that are offered by different manufacturers, there is a possibility to set a value based on Rodinal developer himself. The simplest version of the so-called Parodinal consisting of water, acetaminophen tablets ( acetaminophen ), sodium sulfite and sodium hydroxide. In a simple way, thus from cheap and widely available ingredients, a developer will be made ​​, which is very close to its characteristics Rodinal.