Our foundry has suggested the following regarding Boaz Vaadia Bronzes:
When installed outside, bronzes
naturally change color as they age. If one desires to minimize this natural
reaction (some people like the change), it is recommended that the bronzes
be waxed four times a year at the beginning of every season. The wax that
is recommended is either "Johnson" or "Butcher's White Diamond" Clear Paste Wax. This wax can be
purchased in any hardware store and can be applied with a natural hair
brush (do not use any brush which is abrasive and can scratch the surface.)
In very severe weather conditions additional waxing is recommended.
For more detailed information please download this PDF document.