Re: gum preservatves
What you describe is often used as a "classic" catalyst for polyester monomers in order to create a solid reacted resin. The dimethyl pthalate is a plasticizer for many resins. As you suspected, neither of these are preservatives. The MEK peroxide is closer to rocket fuel as a matter of fact.
As for a preservative, if you like the thought of essential oils have you tried clove oil? This was used and is used for preserving things like hot hide glue so that it doesn't "go off" quite so quickly. As I am not a gum printer (yet) I can't say that it would work for you.
Judy Seigel wrote: