6% sodium sulfite ???

6 grams of sulfite per 100 ml of water will give a 6% solution. If you need to make a percentage solution you can figure it by the number of grams per 100ml of water. 10 grams in 100ml of water is a 10% solution. 100 grams in 1000 ml of water is the same strength, just a larger quantity.

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With the Rodinal, mix the sulfite first in the total volume of water & then measure out the developer and add the sulfite solution to it to dilute to a working solution.

That's 6g sulfite in 100ml water, or 60g per liter. Or, roughly, a full plastic 35mm film cannister. The concentration isn't critical at all.

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Often using Rodinal results in a decrease in EI by up to a stop (from the manufacturers rating) when the film is developed to a "normal" CI. Adding a small amount of sodium sulifte (10g-25g/L) can bring the speed up a half-stop or more. More sodium sulfite adds some solvent effect but Rodinal-developed negs will still be grainier and have higher acutance (but less fine detail) than negs developed in a "standard" developer such as D-76 1:1.

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I always add the Rodinal to the water first, then the sodium sulfite; I doubt it really makes any difference.

Unless it's stated otherwise, a percentage mixture of a solid in solution is always assumed to be weight per volume (W/V). So as the others have already said, it's 6gms of Sulphite per 100ml of water. Sodium Sulphite dissolves very easily in warm water, and you'll have no trouble mixing it.<br>Just to be perfectly clear: The 6% solution of Sulphite is with respect to working strength Rodinal, after it's been diluted 1:25 or 1:50, not 6% Sulphite added to the concentrate. 6% Sulphite in the concentrate would have no visible effect at all.

You may want to consider making a 12% solution of sodium sulfate by dissolving 12 grams of solid in enough water to make 100 ml of solution. You can then dilute this in half when you make the working strength Rodinal.

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For example, if you make 500 ml of working strength developer, then you would reduce the amount of water by 250 ml and use 250 ml of the 12% solution instead. This will result in a final concentration of 6%. This might be easier than dissolving the powder each time.

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Dave

Hi all, thanks for your responses. I hate to append my question at this point, but my original reason for asking the question was I thought I would try to turn Rodinal into a solvent developer for a finer grain. The wisdom of this seems to be debateable. So now the question is, is it worth adding 6% sodium sulfite to Rodinal, and if so, when do you do it. For instance, do you add it only when you are using Rodinal in dilute mixes, when you are using it as a compensating developer? Or is it just cheaper and easier to use D76 in the first place. Thanks, David

As has been indicated above, Rodinal is essentially an acutance developer - it is grainy. Adding the sulfite is generally more to gain some speed (the sulfite has some solvent action which makes it easier for the developer to access some of the latent image speecks). Increasing the sulfite might increase the solvent effect but the decrease in graininess will not be immense. If you want fine grain, you might do better to stick with D76, D23 or XTOL. If you want some sharpness with a minimum sacrifice of fine grain, try D76 at 1:1 or 1:3. Alternativelt, look at staining developers based on pyro or catechol e.g., PMK. The reason those will give you fine grain is because a) you will literally underdevelop the silver image (since much of the image density comes from the stain) and b) the stain fills the spaces between the silver specks to further reduce perceptions of grain. Good luck, DJ.

If you want finer grain you'd do much better to use D-76 or ID-11 at dilutions of 1:1 to 1:3.

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Although adding some sodium sulfite to Rodinal will reduce the graininess slightly, the operative term is "slightly."

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Also, a very careful examination of the negs at high magnification will show that while the Rodinal negs have more acutance, the D-76 negs actually resolve somewhat finer detail. Rodinal sort of raggedly eats the edges of detail.