It's easy to mistakenly buy something in the wrong size, even when you're shopping for yourself — and especially so when you're perusing pre-owned items. The reason why is simple: clothes are bigger today than they were 50 years ago. The United States, and thus the brands operating within its borders, did away with its codified size scale in 1983, kickstarting the sizing free-for-all we face today. By virtue of there being no universal sizing scale, what was considered a small pre-1983 is no longer if you adhere to today's understanding of the size.
But that's not even the whole issue. Nowadays, no two brands construct clothing with the same sizes in mind. A large at J. Crew, for example, might be a medium at Buck Mason. Are you following? Look at Esquire Magazine's 2010 piece, "Are Your Pants Lying To You? An Investigation." In it, a size 36 pant from H&M really had a 36-inch waist. The size 34 pant from Old Navy actually measured out to 39-inches. That's vanity sizing, "the practice of assigning smaller sizes to articles of manufactured clothing than is really the case," the Oxford English Dictionary states. Even if you've studied up on the intricacies of each company, your mastery of sizes doesn't translate to vintage clothes. They're two different languages.
So, if you're buying new, it's best to try things on and form your own understanding of the given brand's label methodology — and maybe you already have. Perhaps you're here because you accidentally shrunk your shirt in the wash. Way to go. But don't worry, this fix is for you, too.
For those of you shopping vintage T-shirts, measurements — like "pit to pit," as Monarch Studios owner Sean Flynn, puts it — are your best guidance. If you're buying a graphic T-shirt printed on an obscure blank by a now-defunct company, there's no way of copping two to compare sizes. Hell, the one you're bidding on could be the last of its kind. So what happens if the T-shirt — or pants, because this method works on them, too, with varying degrees of success depending on the material — you just bought is too small, because it's labeled a men's large but is truthfully a tight medium or tagless altogether? You stretch it. Here's how.
First, buy a bucket.
Get a bucket big enough to fit the T-shirt you're going to stretch.
Fill the bucket.
Fill the bucket with warm — basically hot — water. Next, pour in a teaspoon of hair conditioner. Don't stress over buying an expensive iteration. Mix until combined.
Put the T-shirt in the bucket.
Put the T-shirt in the bucket.
Let it sit.
Leave the T-shirt in there for half an hour.
Slide your arms inside the shirt as if you were putting it on, but don't. Stop short of sliding your arms through the armholes. Open your arms, stretching the torso horizontally. Do it gently and without pushing too hard where your hands might be. Just as hangers leave raised marks on the shoulders of shirts, pressing too hard on one spot can leave a permanent peak.
How I see it, you have two options: pin the neck of the T-shirt under something heavy and gently pull at the hem, starting at the edges and working your way in; or, hold opposite corners of the T-shirt (top left shoulder, bottom right hem) and alternate tugs. The former will work for increasing the length by at least one size, while the latter grants just a little wiggle room.
Let it dry.
Don't toss your T-shirt in the dryer. That'll undo all of your hard work. Let it air dry. But, if you can feel or see conditioner still, rinse it out.
Try it on for size.
Once it's dry, give it a try. But remember: you can really only stretch a T-shirt two sizes — ~four inches pit to pit and ~three inches length-wise. Any further and you're better off selling it to someone else (who wears that size) instead.