Yes, it will contract when you put it in the freezer, but the most pressure differential this can possibly cause is 14.7 PSI, and Boston rounds up to 500 ml in size have no problem handling that pressure.All my nic is in a 50/50 base so it contracts considerably when frozen. I am trying to figure out the safest way to bottle it for freezing that won't result in a lot of shattered glass. I'm thinking that I should decant it into the bottles chilled, fill each bottle 3/4 full and top with argon. Any thoughts?
I use 120ml bottles almost exclusively. I've never had one break going into our coming out of the freezer. I do nothing special like pre-chilling, and some of my bottles have been though a bunch of cycles. I re-use bottles every time I make a big batch of vaping-strength unflavored liquid, and I keep all of that except one bottle at a time in the freezer. My unflavored is 65VG, rather than 50/50, but I've seen straight PG and straight VG both contract at freezer temperatures, so I don't think the ratio makes much difference.