Shelf life of Neofin blue?

Getting ready to try this developer out, but have not used it before. How is its shelf life once it's diluted in water?

In short - Not very long.

Perhaps a day or so but then that's it.

The developer should be used within an hour after dilution.

BTW, if you obtained the developer from Photographers Formulary it's not Neofin Blue. The formula for this developer was proprietary and was never published. What you have is the Beutler formula or someone's guess.

The formula for Neofin Blue has changee several times over the years since its introduction. The latest MSDS from Tetenal lists potassium carbonate, DTPA Na5, metol, phenidone, and hydroquinone. The sodium sulfite is not listed since it is not considered to be dangerous.