The typical process for opals that come from Queratero in Mexico is to let them dry out for several months or longer on a sunlit windowsill. Those that do not crack or go milky can a be sold. Trapped water molecules have a lot to do with the appearance of opal, and apparently yours do not retain the water necessary to make them translucent and/or give them fire. It is pretty typical for opal to be displayed in jars filled with water and having a curvature that magnifies the stones within. It is also typical for the savvy buyer to ask to see the stones outside the vials of water. Fire opal, the kind with no play of color which is faceted for its color, should be displayed and sold dry for the obvious reason you have seen. I don’t know of any way to seal in the water reliably. I would chalk this up to experience and go on to enjoy other stones and to educate myself further. Ethiopian opal, interestingly, loses its play of color when wet, but regains it when it dries. That’s quite disconcerting when you start to cut one and the fire all disappears! -royjohn