DIY Rodinal, are the crystals needed?

Rafael Saffirio · May 26, 2022

Hi, I did my second batch of homemade rodinal https://varezers.org/rodiynal/ in the first batch I keep the crystals on the bottle but I had to filter the diluted developer before using it because it has a lot of stuff floating, Can I just filter the whole batch after waiting 3 or 4 day and the bottle it? or the crystal are somehow needed?

AgX · May 26, 2022

In an equilibrium state a precipitate could be taken off, without effect on that equilibrium.

BUT this would apply only as long the environmental situation is not changed.

Bronson Dugnutt · May 26, 2022

Try warming the entire bottle in a water bath to re-dissolve the crystals before performing a mechanical filtration to remove other solids. Crystals of sodium salts will form in such a highly concentrated solution, potentially altering the pH of the remaining liquid and affecting developer activity, especially at high dilutions.

I have a batch of homemade rodinal formulated with potassium hydroxide that is about 3 years old with no signs of crystallization, owing to the potassium salt's higher solubility.

revdoc · May 27, 2022

When I make parodinal, I often get undissolved sodium sulfite crystals, especially if the temperature drops. There is enough sulfite in the developer without them, so they can be left or removed.

The original Rodinal uses metabisulfite rathe than sulfite, which is more soluble than sulfite. That is why you don't always see any crystals in the commercial product.

Raghu Kuvempunagar · May 27, 2022

Rafael Saffirio said:
I had to filter the diluted developer before using it because it has a lot of stuff floating,

If the crystals were Sodium sulphite, they should have dissolved readily in the diluted developer. I suspect that the floating stuff is probably not sulphite. Btw what colour do the crystals and floating stuff have?

Rafael Saffirio · May 27, 2022

revdoc said:
The original Rodinal uses metabisulfite rathe than sulfite,

I had no idea about the metabisulfite, is the same amount as sodium sulfite?

Raghu Kuvempunagar said:
Btw what colour do the crystals and floating stuff have?

Like this

Raghu Kuvempunagar · May 27, 2022

Oh you're using Paracetamol tablets! The floating stuff could be some filler material (i.e. inactive ingredients) in the tablets.

Marcelo Paniagua · May 27, 2022

Raghu Kuvempunagar said:
Oh you're using Paracetamol tablets! The floating stuff could be some filler material (i.e. inactive ingredients) in the tablets.

So ok to filter. Normally use some cotton or Even coffee filter in a regular basis. I don't think there in any effect. Do high dilutions all the time and performance is consistent enough.

DIY Rodinal, are the crystals needed?

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