Ron, sorry I hadn't checked the Formulary's website I'd made a note that it was an alternative source since Rayco closed up. I wonder if it's a difference in manufacture between US/Europe a bit like Sodium Bisulphite & Sodium Metabisulphite, or perhaps it's just availability.

I don't think there's many people left who make up their own colour chemistry any more so demands probably very low.

Ian