I use protective gas which effectively prevents oxidation. Gourmet (wine?) shops sell these gases for half empty wine bottles (solitary drinkers exist), Tetenal (Germany) makes product -"Protectan", if my memory serves me right, specially for photographic purposes or you can use plain butane gas as used for filling lighters etc. All are heavier than air.
Using butane is extremely dangerous, not only is it a fire hazard, but the chances of having a bottle of chemistry explode is quite high, getting embedded with plastic shrapnel is bad, having that shrapnel coated in potentially toxic liquid, could be deadly.
