Hmm, not sure if my post got deleted, or if I didn't post it.
Anyway, using foil over the mouth will keep any dust from settling inside the bottle during storage, sure. Those caps you bought were also undoubtedly intended for "recapping" opened bottles to be stored in the refrigerator, and were never designed to see heat.
Once the hot air cools, it contracts and pulls in atmospheric air. No more sterility, even with a tightly crimped foil cap.
Dry heating bottles doesn't clean them either. If it's not clean from debris, you'll never be able to sanitize it. Those bits of stuff are perfect breeding grounds for the junk that floats around in the air that just got sucked in to the bottles as they cooled, too. Scrubbing or a jet of hot water/B-Brite/PBW/Oxi-Clean Free is the only way to dislodge the garbage that beer leaves behind inside a bottle. You can't see it, but it's there.
Drastic heat-cycling also affects the long-term durability of glass. No bottle is structurally perfect, and the imperfections - scratches and thin spots - will become weaker and weaker. One day you'll open your case of bottles to find a fallen soldier and a mess on the bottom of the box. No fun. I've been there.
A quick rinse of sanitizer just prior to bottling is ideal even after baking, just to rinse any dust. Star-San can be reused, and it only takes a small amount poured into the bottle to be effective. Pour it from one bottle to the other, or use a
Vinator like this. I use a vinator and I'll blow through 2 and a half cases of bottles in under 10 minutes - with a hangover. Thing is stupid easy to use. Surely you're using Star-San or some kind of sanitizer for your equipment, right? Why not redirect a few ounces for your bottles?
The bottle is where your beer develops, matures, and if appropriate, ages in. Why not ensure the utmost cleanliness and give your beer a proper resting place? There are better places to cut corners and save time on. And if you don't like cleaning bottles, well, that's what minions are for! You'd be surprised at how well free beer motivates people.
Whatever you decide, just make sure you do it the best way you can. As long as you enjoy your beer, then what is anyone gonna say to change your mind, right?
I can still try though, can't I?
as an aside...
Sometimes you don't (or can't) spend the money on sanitizer
This terrifies me. Brewing without sanitizer is like riding a motorcycle at 100mph with no brakes in the rain sitting backwards and blindfolded while under out-of-body hypnosis. I've been broke, I know how it is, but if you can't scrounge the 4 bucks for Iodophor or 7 bucks for Star-San, you should probably be spending what little cash you have on things like food, not a luxury item - and hobby - like homebrewing.
Sorry if that came out harsh. I come from a place of love!
