Bidda,
I have no credible ideas on how to remove the effect, if possible to do so. I have seen many suggestions about denture cleaners, bathroom cleaners, vinegar etc., but it appears that 9 times out of 10 those methods do not work, but people still enjoy passing those suggestions on anyway.
Myself; I pretty much leave that sort of thing where I find it, since I prefer to buy nice, good condition glass items, rather than science projects that may not be resolved, leaving me with something I paid good money for on a gamble and end up not wanting in the end. I just play it safe I guess and never allow myself to be too desperate to have something, meaning I collect glass as a leisure time activity only, so the searching and waiting are just as enjoyable as the finding.
Mike