"What finish will let purpleheart keep its purple color?"
That is a good question. I don't really know. The manual I have at hand claims that it is exposure to air, and specifically refers to wax as being effective (it is vague about other finishes).
Do keep in mind that some twenty species are involved which will differ in chemical composition, and thus in degree of reaction.
Over time this question was posed various times on the wreck, and no clear consensus emerges. First coats are mentioned of shellac, oil, etc with varying results. Some people has objects that remain purple for years.
It might be worth putting this question again to the NG. Steve Knight has been making planes of purpleheart for quite awhile now and sold them to members of this NG: it might be interesting to see how well they keep their color. AIUT, Steve makes a selection for one particular kind of purpleheart. PvR
"Max Mahanke" schreef
and I imagine would agree with your entire posting. However, when faced with the question, what causes purpleheart to revert from the vivid purple to its purplish brown color over time he didn't know for sure. In researching this on the web, one camp says exposure to UV over time and the other camp says oxidation. The UV camp says use a finish with UV blockers and the oxidation camp says use a water-borne finish.
remedies for each sound reasonable; or is UV and oxidation one in the same, that is, does UV accellerate oxidation which in turn causes the color change. I accept the Budhha's statement that all life is impermanence - I just want to do my best at slowing it down as much as I can.