the comment that these things are uncleanable, has been largely invalidated in recent times with the advent of 'Magic Balls'. Small pots of these copper coated balls - which are sold specifically for cleaning decanters and vases - may be used with or without a liquid additive (i.e. metal polish) - and can achieve very good results. I would, however, agree that there remains a small percentage of glass pieces that, either due to glass make up, or chemicals in the water, will defy improvement by this method, in view of the 'damage' that has occurred to the glass. If it is just a matter of
cleaning, then these copper balls should do the trick