Mr. B.’s fourth grade teacher wants empty 2-liter soda bottles for a classroom ecology study. Being a classroom parent, I didn’t stop at one Coke Zero bottle for Mr. B. but have plunged on to get more. The only hassle is the label. Most of it can be cut off, but it always leaves some where the glue is.
The glue comes off easy enough with WD-40, something I discovered years ago trying to get dried glue off fiberglass. But the label residue itself, ugh, what a pain. Scrape, scrape. Mrs. Charm suggested immersing the bottle in hot, soapy water. I even left it soaking overnight. Didn’t work.
This fellow managed it with slightly-cooled boiling water poured into the bottle. I may have to try it, though it sounds like a great way to ruin, or at least deform, the bottle’s thin plastic. If there’s a surefire trick here, I have yet to find it. Anybody have any suggestions?
UPDATE: Have noticed several visits from folks seeking info on this subject. Therefore will add that I wound up doing in the neighborhood of twelve bottles and this process works best: cut off the label and spray the label residue with WD-40. Let it soak a while and then use a razor blade in a holder to scrape it off. Corner of the blade works best. Once the label is off, spray more on the glue, wait a bit and then wipe it off. Wash and dry the bottle to get the WD-40 off.
THE TEXAS SCRIBBLER 
The warm, soapy water used to work fine when the labels, per se, were glued on paper. They are not made of paper any more, they are (most likely) polyethylene. The bottle itself is (probably – they used to be, at least, last time I analyzed one it was) polyethylene-terepthalate, PET. PET can take a lot of heat. Boiling water temp, not much of a problem, though it does weaken as it heats.
WD-40 should work for all of it, as mostly all adhesive polymers are oil soluble.
Lots of tennis shoes, for instance, if polyethylene, is about 20% by weight some sort of oil. They’ve probably changed the recipe by now, but probably only as to the variety of oil, i.e., aromaticity/paraffinicity.
Technical enough for you, Scribbler?
jd
As usual you have me on the chemistry explanation, JD. Sounds like I should try the boiling water, slightly cooled. I have been using the WD-40, but it still involves a lot of scraping to get the label residue off. Thanks.
Er… alcohol? Vodka, if no ready pure alcohol?
Alcohol might work, but I decided to stick with the WD-40 after JD’s explanation of the label being oil-based. Also switched to using a razor blade for the scraping. The combination works pretty well, though the whole process still takes a while.