This isn't a complicated thing, but it's kind of an involved story, and I have pictures, so what the heck.
I've been infusing gin for a while now, and sealing the bottles with electrical tape. It actually looks OK, but I've thought I could do better. The photo essay described above shows my process for sealing the bottles with heat shrink tubing. I thought about writing a long and complicated blog post describing the process, but I think the pictures make it pretty obvious. Here's a few extra notes… First of all, finding 30mm heat shrink tubing is tough. It turns out that the main seller online is http://monoprice.com, which I've used successfully for cables in the past: all the other sellers seem to be just buying from them and reselling, as evinced by the photos on their pages :-). Which is fine, except that Monoprice was out of stock for a couple of months, and worse yet they only sell a 100' roll. (You can tell you're in the US when you're getting 100' rolls of 30mm tubing.)
I ordered my tubing the day it became available: $15 + $8 shipping, more than I could understand at first. It came in a giant box, with a ton of packing: I guess heat shrink tubing is delicate :-). The delivery guy showed up on the snowiest day of the year here, which was kind of neat, if totally unnecessary.
Then the next disappointment: the Monoprice tubing has a bunch of printing silk-screened onto the outside. Clearly not OK aesthetically. The printing is not water-soluble. Rather than trying ethanol, acetone, or (Heaven help us) xylene, I figured out that I could turn a short piece of tubing inside out. Problem solved.
Most of the rest of the process is straightforward. Note that you'll be heating the neck of the bottle: if you don't get a good lip over the top of the cork, it can (and did) shoot out of the bottle and straight into the air. The heat gun I'm using is way more than you need: I'm using it on its low heat setting, and trying not to linger anyplace. The tubing shrinks quite easily.
So there you are. Enjoy! (B)