Science proves that you should wear glittens

They're the mullet of cold-protective clothing. Half glove, half mitten — really, fingerless gloves with a handy mitten flip-top.

They are also fantastic.

Now, partly, this is a matter of personal opinion. But partly, it's just good science.

Before you spend your weekend outdoors, or take your next chilly commute, let's talk briefly about glittens — and the science that makes them superior hand covering.

There's really two things going on here.

First: Mittens are warmer than gloves.

I spent years feeling like I failed at gloves. Even high-quality Isotoner-type things couldn't keep my fingers warm. At least, not for very long. After 10 or 15 minutes, my fingers would start to go numb and cold. The only way I could keep them comfortable was to slide my fingers out of the finger holes and ball up my hand inside the wide part of the glove. (At which point you become Edward FloppyFingers.)

And there's a very good reason for this. It has to do with the way we get cold.

Everything wants to be the same temperature. Hot things and cold things want to match, rather than be different. At the same time, it takes energetic work to make things hot — whether that's a furnace pumping in your basement, or the sun burning in outer space, or your body metabolizing food. Without those inputs, everything is cold. (Eventually, everything will be cold. Inevitable heat death of the Universe and all that.)

So hot things are special. And when they come into contact with cold things, heat moves from the hot thing to the cold thing, and the hot thing cools down. In fact, the bigger the difference in temperature between the hot thing and the cold thing, the faster the hot thing is going to become cold.

There are several ways that this heat transfer can happen, but when we're talking about your hands and the cold air, we're talking about convection — the transfer of heat between a solid object and a fluid. (My husband, an HVAC engineer, refers to this as, "One of my three favorite kinds of heat transfer.")

Cold air moves over your hands. Your hands and the air try to become the same temperature. Your hands get cold. You can't stop this process, but you can interfere with it, and that's what hand coverings are all about. Insulation — the cloth of the glove or mitten — creates a barrier between your warm hand and the cold air.

It's not a perfect barrier. But now the thing that is most in contact with your hand is closer to the temperature of your hand. With less of a temperature difference, heat transfer slows down.

But there's another factor that affects heat transfer — surface area. The more surface area on the hot thing, the more it comes into contact with the cold thing, the faster it loses heat. Gloves put more surface area in contact with cold air than mittens do. So they won't keep your hands as warm as the same amount of insulation in a mitten will. What's more, gloves force each finger to fend for itself. In a mitten, fingers are in direct contact with other fingers. They can share heat through the solid-object-to-solid-object process of conduction and help keep each other at a relatively stable temperature.

Downside to mittens: You can't use your cellphone, or your house keys, or really anything that requires you to be more dextrous than the average 18-month-old.

Second: Glittens offer more manual dexterity than mittens.

With the science firmly established, we now get into the personal preference portion of this review. From my experience, glittens offer all the warmth of mittens, plus the manual dexterity of gloves. In fact, with their help, I've stood outside in Minneapolis at a bus stop for 30 minutes while playing with my Android phone. I had to switch hands a few times. But, overall, my hands and fingers stayed warmer, longer — even with occasional fingertip exposure to the cold air — than they do when completely covered by gloves.

In mitten mode, my fingers are better protected and they can heat up each other. In glove mode, I can work my phone's screen. It's a win-win situation. And it's all thanks to thermodynamics.

A Harvard animation by Dale Muzzey demonstrating the importance of surface area to heat transfer — and other things.

Image: IMG_6027crop, a Creative Commons Attribution (2.0) image from 97793800@N00's photostream