Picked up a bottle of Rodinal

Uncle Bill

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I read an article that it remains perfectly usable after it has turned from the straw colour to that of tea. My bottle of Rodinal looks like well steeped earl gray tea, is it still ok?

Bill
 

reellis67

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Should be fine. Mine routinely gets dark and I've not seen any problem developing with it like that. There are stories that float around about 50 year old half-full bottles still working fine, but no one can proved hard evidence to substantiate it, at least that I've heard. I think you will be fine just the same - the stuff is just about eternal in my experience, but if you are really concerned about it, try a test roll first.

- Randy
 

Travis Nunn

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My half full bottle of Rodinal is pretty dark and I've noticed no ill effects.
 
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Uncle Bill

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Thanks for the reassurance Travis. I have read that Rodinal has a long....really long half life. Its time to branch out from HC110.

Bill
 

Donald Qualls

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The Parodinal that I make from acetaminophen tablets doesn't have anything like the longevity of Rodinal, but it still works when the *working solution* looks like moderately strong tea -- the concentrate, at that point, looks like cold coffee or flat cola. Some have reported keeping this homebrew for six months without loss of activity, and I'm no longer sure the drop-off I saw in my first batch was actually significant; it might just as easily have been due to the method used to process that last batch of film.

Genuine Agfa or A&O Rodinal ought to still work when the concentrate is as dark as espresso, as long as a few of the crystals remain in the bottom of the bottle.
 

Petzi

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What's so interesting about the bottom of your bottle?
 

reellis67

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Sounds like the middle of a bad joke doesn't it?

I can't see if there are still crystals down there or not due to the color, but every sheet/roll turns out fine so they must be down there...

- Randy
 

gainer

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Get some p-aminophenol base from Photograper's Formulary or elsewhere. If you can't see crystals, put a little of that in the bottle. It won't clear it up, but it will put crystals in the bottom of the bottle.
 

Gerald Koch

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Donald Qualls said:
Genuine Agfa or A&O Rodinal ought to still work when the concentrate is as dark as espresso, as long as a few of the crystals remain in the bottom of the bottle.
Click to expand...
Once Rodinal is made the existence or non-existence of crystals in the bottle has no effect on its keeping qualitites.
 

Bruce Osgood

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The little bit of Rodinal I have left is brown and works very well. I shake it up before diluting to working strength, is this perhaps a no-no?

Originally Posted by Donald Qualls
Genuine Agfa or A&O Rodinal ought to still work when the concentrate is as dark as espresso, as long as a few of the crystals remain in the bottom of the bottle.
 

Gerald Koch

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After a bottle of Rodinal is opened and exposed to the air, carbon dioxide may be absorbed by the solution. This lowers the pH of the solution causing some of the paraminophenolate salt to decompose back to paraminophenol base which precipitates. The strength of the developer is a bit less but unless a large amount of CO2 is absorbed it should be fine.
 

Bruce Osgood

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So, shaking up the bottle prior to mixing is ok?
 

Gerald Koch

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The small amount of paraminophenol precipitate should dissolve when the concentrate is diluted. However, I would be tempted to filter the working solution before use to catch any remaining solids that might still be there.
 

gainer

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OTH, should not oxidation of p-aminophenolate cause increase of pH and conversion of some of the precipitated p-aminophenol base into the salt?
 

Donald Qualls

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gainer said:
OTH, should not oxidation of p-aminophenolate cause increase of pH and conversion of some of the precipitated p-aminophenol base into the salt?
Click to expand...

This is the reason (or so I've understood) for keeping the crystals -- they're critical to ensuring a reserve of developing agent against oxidation. The brown color is due to oxidized developing agent; the developer keeps working because, as some oxidizes, more dissolves. And even if you keep the bottle for twenty years, unless you routinely open it without removing any concentrate, you'll use it up before you run out of crystals in the bottom.

Randy, the big thing is, if you (for some reason) decant the liquid from the original bottle, be sure to shake or stir immediately before pouring, so that you carry over the crystals to the new container. According to folks who know a lot more about developer chemistry than I do, they're what gives the Rodinal its longevity.
 

Gerald Koch

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Fresh Rodinal should not contain any solids as it is filtered before bottling by the manufacturer. The small amount of solid that later forms is insignificant as a source of developing agent compared to the amount of developing agent in solution.

The pH stated by Agfa in their MSDS is ~14. That is about as high as can be obtained in aqueous solution. The pH is so high that when Rodinal was supplied in glass bottles it actually etched the inside of the bottles much like concentrated sodium hydroxide solutions will. The silica in the glass is acidic enough to be dissolved under these conditions.
 

gainer

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Assuming that it is mostly superstition that crystals in Rodinal behave like a replenisher, still what can it hurt to cater to the superstition? Excess p-aminophenol jusr lies there like lump for the most part. Aerial oxidation of the stock solution through exposure of the liquid contents to the gaseous contents of the bottle, considering the concentration of the stock, doesn't seem to me to be much of a threat to activity.

How much fully oxidized p-aminophenol does it take to make half a liter of Rodinal stock be really dark? Not much, I think, considering the agent is related to many dyes.

The MSDS specified pH probably refers to the stock. I don't think much of the uncombined KOH would be found in the solids you might recover from vacuum evaporation of the stock. Put the water back in and you could detect all the ions of the chemicals you put in to make the stock. Still, putting a finger into Rodinal stock is probably (I'm guessing) not going to be the same as putting your finger into KOH solution. It doesn't take a lot of KOH to make a liter of solution with pH near 14 anyway. You might find that amount in some soft soaps you put in your hair. A very little ascorbic acid will bring the pH below the point where development takes place in my lifetime. I got some complaints to that effect from some who tried my suggestion of adding vitamin C to Rodinal without noting that I said to use the ascorbate.

What most of us who have used Rodinal know from experience is that color is no clue to activity. Initial pH is high, but buffer capacity is not so high. There are enough recipes for home made Rodinal that no one is quite sure which is the Real McCoy (or the German equivalent.) All these recipes work given the right development time. It's fun to play with, and in the right hands is capable of seriously good work.
 
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