The formula for Rodinal R09 has never been officially published by Agfa. In the "Agfa" Book of Photographic Formulae, published by the Berlin Aniline Company in 1910, the company tells us:

As "AgfA"-Rodinal contains only traces of carbonic alkalies, the use of distilled water for dilution is not necessary. In connection with the use of "Agfa"-Rodinal the following remarks should be carefully noted:

In addition to neutral sulphite and water "Agfa"-Rodinal contains only an alkaline salt of Paramidophenol, but no excess of caustic alkali.

PDF Rodinal 1910

However it's possible to make formulae that's close to the current versions.

Original Rodinal contained p-Aminophenol (once called Paramidophenol by Agfa) and this was formed by precipitation of the free base from p-Aminophenol hydrochloride using sulphite and carbonate (hence Agfa's comment "contains only traces of carbonic alkalies".


The formula for Rodinal has changed and evolved presumably as high grade p-Aminophenol free base became commercially available, allowing Rodinal to be completely free of carbonates.

J. Desalme published a " Concentrated Paraminophenol Developer of the Rodinal Type" in 1913, this was later included in L.P. Clerc's book "Photographic Theory and Practice".

Sodium Carbonate & Sodium Sulphite are added to a solution of p-Aminophenol Hydrochloride which precipitates the free base, which is filtered and collected.

The paste of p-Aminophenol free base is then added to a solution of Sodium Metabisulphite and Sodium Hydroxide added until all the free base is dissolved, finally a small amount of Metabisulphite is added until the first crystals of p-Aminophenol free base begin to form again.

This mirrors Agfa's own description of early Rodinal, and accounts for the traces of carbonates, and the "no excess of caustic alkali". (J. Desalme was a photographic chemist specialising in aminophenols and other developing agents particularly for colour processing).

Now we reach a point of contention "Free base" or "Hydrochloride", genuine Rodinal has always been made using the Free base of p-Aminophenol . (50g of p-Aminophenol is equivalent to 66.2 g p-Aminol hydrochloride). There is no evidence to suggest that Rodinal of any form has ever contained p-Aminophenol Hydrochloride.

The MSDS sheets for both Rodinal and Calbe R09 show clearly that both developers contain p-Aminophenol free base (CAS 123-30-8) and not p-Aminophenol hydrochloride (CAS 51-78-5).

Making a Rodinal substitute with p-Aminophenol Hydrochoride will leave free chlorides in the solution, and neutralise more Hydroxide, the amount of developing agent would need to be increased along by a factor of 1.33 and also more KOH added.

Data on early Rodinal is hard to find but in a thread on Photo.Net "Edward Zimmermann" wrote:

The formulas for Rodinal, resp. R09 (1964 to present), have never been published. The patent is for Paramidophenol developers and there are many recipes making the rounds since the late 1800s. One of the most famous is attributed to Eder. From my copy of Spörl and Neumann, "Fotografisches Rezeptbuch" 1943 edition, p.50):

N16:

  • Paramidophenol 50g
  • Kaliummetabisulfit [Potasium Metabisulfite] 150g
  • Wasser 625ccm (ml)

Then a solution of

  • Ätznatron [Sodium Hydroxide] 215g
  • Water 500ccm (ml)

is slowly added untill the cloudyness breaks. According to the book it says this is typically around 350ml.
Then the solution is diluted with water to make 1 liter.

My note: 350ml of the Sodium Hydroxide solution contains 150.5 gms Sodium Hydroxide.

The same formula was published in the British Journal Photographic Almanac (1910 & earlier) as:

Paramidophenol.
ONE-SOLUTION

Potassium metabisulphite 300g
Distilled water 1 litre
Paramidophenol 100g

Dissolve in the above order and add gradually:
Caustic soda or potash to dissolve the precipitate first formed.

For use, dilute 1 part. with 10-20 parts of water.

No final volume of solution is given but it's likely to be 2 litres if you want the equivalent of early Rodinal.

It's important to note that these sources clearly indicate the use of the free base, as they go on to also include p-Aminophenol Hydrochloride film developers. These are in the 1910 "Agfa" Book of Photographic Formulas, the 1910 BJP Almanac and Ed Zimmermann's book all from quite different sources & countries.

However other versions of this formula appear in various books from the early 1900's onwards, but using p-Aminophenol Hydrochloride, because of the difference in Molecular Weight and the effects of the additional Hydrochloride they won't be quite the same. Dr M. Andresen, of Agfa, who discovered & patented p-Amaninopheol and designed Rodinal published it himself in the "AGFA Photo-Handbook" he did not claim it was similar to Rodinal, listing it as - Formula 21: Concentrated single solution. (As above proportions but using p-Aminophenol Hydrochloride).

L.P.Clerc and others indicate that Potassium Metabisulphite was the preferred source for the Sulphite in Rodinal, Potassium salts are used in preference to Sodium because of their greater solubility in water which becomes far more important in concentrated developer solutions. Metabisulphite and Hydroxide form Sulphite in solution.

At some point before or during WWII Agfa began using Potassium Sulphite and also adding Potassium Bromide and an anti-foggant to Rodinal. It's entirely possible that Agfa modified Rodinal so that it was more suitable for roll & particularly 35mm films which became cfommon in the 1930's.

Some have made the assumption that this formula might be "Classic Rodinal" but if we compare it to a modern MSDS's it's only close s to Calbe's R09 MSDS for the p-Aminophnol.

P-Aminophenol 50g - 5%
Potassium Metabisulphite 150g - 15%
Sodium Hydroxide - very approx 150g - 15%
Water to 1 litre

Calbe R09 MSDS

P-Amininophenol 5%
Potassium Sulphite 30%
Potassium Hydroxide 4%

However Potassium Metabisulphite is quite acidic in solution and will neutralize a considerable proportion of the Hydroxide. Replacing it with Potassium Sulphite cut's the amount of Hydroxide needed very substantially. Potassium Metabisulphite 5% solution has a pH of 3.8 - 4.6, while a similar Potassium Sulphite solution has a pH of 9 - 10

Only one parameter seems to stay constant from early published alternatives through to Orwo/Calbe R09 - the fact that Rodinal is a 5% solution of p-Aminophenol free base in a sulphite solution, with no excess of alkali. It's reported that the Calbe product usually has a few crystals of the free base in the bottom of the bottle, which indicates no excess of Hydroxide.

The British RAF report into the "Agfa Film Factory - Wolfen" reported by G.C. Brock, London : H.M.S.O. gives a formula for Rodinal as:

Dissolve 34 kg of para-aminophenol in 340 litres of water. Add 558 kg of a 30% solution of potassium sulphite at 55C followed by 50 kg of a 34% potassium hydroxide solution, then 5.52 kg of potassium bromide in a little water. Add 42 g P.1347 (an Agfa-specific anti-foggant). Filter and allow to stand for 14 days.

Knowing the Specific Gravities etc this seems to be around:

p-Aminophenol 34kg
Potassium Sulphite 128.08kg
Potassium Hydroxide 12.57 kg
Potassium Bromide 3.75 kg

We aren't given a final volume, but if we relate this to the 5% p-Aminophenol of the Calbe MSDS this works out as:

p-Aminophenol 5%
Potassium Sulphite 19%
Potassium Hydroxide 1.85%
Potassium Bromide 0.77%

But the Calbe/Orwo version of R09 is the pre-WWII formula and it's MSDS is

p-Aminophenol 5%
Potassium Sulphite 30%
Potassium Hydroxide 4%
Potassium Bromide - not included (below 1%)

Unfortunately we can't really completely trust the RAF report, none of the Allied F.I.A.T. reports about Agfa products is entirely accurate, after all some Agfa employees were former members of the National Socialist Party (Nazi's). There is insufficient Potassium Hydroxide to react with the p-Aminophenol free base, and it is possible the resulting solution was then adjusted until the free base had just fully dissolved.

Patrick "Gadget" Gainer has published "EZ Rodinal" which in terms of its ratio of p-Aminophenol to Potassium Hydroxide is probably close to Calbe R09 as there will be no excess of Hydroxide, the weights in brackets have been scaled to give a concentration of 5% p-Aminophenol.

EZ Rodinal

To 400 ml water, add:
Sodium sulfite (anhyd) 85 g (106.3)
p-Aminophenol base 40 g (50 g)
Stir well. Add
Sodium hydroxide 13.8 g or Potassium hydroxide 19.2 g (24g)
Add water to make 500 ml. (1 litre)

If EZ Rodinal; is adjusted a little further by adding 300 g of Potassium Sulphite in place of the Sodium Sulphite, some Potassium Bromide added plus some Benzotriazole and Potassium Hydroxide added slowly until the free base just dissolves

EZ Rodinal New (Calbe R09 substitute)

To 800 ml water, add:
p-Aminophenol base 50 g
Potassium sulphite (anhyd) 300 g
Potassium hydroxide 24 g
Potassium Bromide 0.8 g
Benzotriazole 1% 10 ml
Water to make 1 litre)

This would be a lot close to the pre War formula and Calbe RO9, although this is itself now being made in a more concentrated form so that the dilutions & dev times are more comparable to Agfa /A&O Rodinal (post 1964)

Patrick's second Rodinal substitute formulae is close to the Bayer/Agfa/A&O MSDS data-sheets for modern Rodinal:

p-Aminophenol 4.1% (A&O)
Potassium Sulphite 30-40%
Potassium Hydroxide 2.7% (A&0)
Potassium Bromide 1-5%
Anti-foggant - not specified
pH 14

Gainer Rodinal Substitute

To about 750 ml of water at room temperature, add
p-Aminophenol 38 g
Sodium sulfite (anh) 160 grams
Sodium hydroxide 23 grams
Water to 1 liter.

This is on the right track, you need to use the free base and an excess of Hydroxide unlike the older R09 formula which has nearly 20% more p-Aminophenol and also requires using at a higher concentration to get equivalent results.

In a post about Patrick's version a comment was made about the pH at 1:50 being roughly 11.6, Agfa Rodinal has a stock concentrate pH of 14 and a dilute pH of 11.55 so if this is the case Patrick's formula is about right, except too little Sulphite and there's no Bromide or anti-foggant.

Agfa's modern Rodinal 1964 onwards uses an excess of Hydroxide and as a consequence is more active despite the lower level of p-Aminophenol than the previous formulae. Calbe R09 concentrate has a pH of 11.8.

This is what I would use as a starting point for a good modern substitute:

Rodinal Substitute

p-Aminophenol.(free base) ................... 41 g
Potassium sulphite (anh) ..................... 348 g
Potassium Hydroxide ........................... 27 g
Potassium Bromide ............................. 10 g
Benzotriazole 1% ............................... 10 ml
EDTA Na4 (optional) ........................... 6 g
Water to make .................................. 1 litre.

If necessary adjust to pH 14

Some notes:
The balance of the Bromide & Benzotriazole may need adjusting upwards..
The mixed developer should be left a couple of weeks before use.

Contrary to what has been written in some books Rodinal has always used the free base of p-Aminophenol although in the early days this was prepared from the Hydrochloride first.

Ian