Seriously. And, in the long run, a marker is far cheaper than purchasing a gazillion disposable cups over the course of a lifetime.

What you need

1. Sufficient glasses for all your guests.
2. A permanent marker that contrasts with your beverage. (So it can be easily seen.)
3. Alcohol in some form. Rubbing alcohol is what I normally use, but I’ve used hand sanitizer in a pinch. Vodka also works. Whatever.
4. A cloth to apply the alcohol with.
5. A BSides Chicago 2014 badge, or other bottle opener.

What to do

If you’re having a small shindig, just give each guest the marker and a glass as they arrive. Have them write their name or some sort of identifier on their glass. The only rule is that it must be on unmarked surfaces. If you or they write on any etching, marking or similar, that writing will be part of that glass forever.

Nobody wants that.

Anyway, with a larger shindig, or one where people will come and go randomly, I advise a sign. The last party like this I threw, the sign made it much easier. Just tell people to select a glass and write their name on the unmarked portion of their glass.

Over the course of the evening, some folks will find that their name has been rubbed off. That’s fine, just have them rewrite.

At the end of the party, or the next day (or in one very sad case we discovered recently, an unknown amount of time well over two months later), use the alcohol to rub the marking off the glass. It will come off easily, leaving no sign behind that there was ever permanent marker on your glass! Then just wash as normal.

What about the cloth? Well, it doesn’t come out in the wash for awhile. Sometimes never. So use a cloth you don’t mind being stained.

Why does this work?

For the same reason water WON’T get the marker off your glass, actually.

I learned the first part of this trick in general chemistry lab, more than a decade ago; before I knew how it worked, I was being told to mark glassware in the teaching labs with a grease pencil on the glass, but not etched, parts of beakers and flasks. I didn’t know why, and as I wasn’t the person cleaning most of the glassware, I didn’t figure it out for ages. (Until I took Organic Chemistry a bit later.)

Very basically (and I’m skipping a lot), molecules come in a few types. The ones relevant to this post are polar, non-polar and a hybrid of the previous two. Specifically, hybrids are larger molecules that are polar on one end and non-polar on the other. The molecules that make up cell membranes are like this, as are a class of products called surfectants (Many detergents are surfactants.)

The difference between polar non-polar molecules comes down to electrons. Polar molecules result from a situation in which the electrons in a molecule spend more time on one “side” of the molecule than the other. This means that even though the molecule has a neutral charge overall, one side of it is slightly negatively charged and the other side is slightly positively charged. Much like a pair of magnets, this will end up with parts of the molecules that will attract each other and parts that will repel each other. Non-polar molecules are better at sharing, so they have no sides with minor charge.

However, because of the charged and not so charged nature of each type of molecule, they do not mix well.

Water is a polar molecule, and is a good solvent for other polar things. (Meaning it breaks them apart well.) But it has no ability to dissolve non-polar things. Thus, it can’t dissolve the marker’s ink. (“Washable” colored markers are, I suspect, more polar than the average marker.)

But a good non-polar solvent CAN break apart the marker’s ink, and can do so easily. Now, technically, alcohol is just a little polar, rather than non-polar, but its effects around the house are often much closer non-polar than polar. And it’s a great solvent. You can probably think of a time you’ve cleaned something with alcohol (and, indeed, I recommend keeping “cleaning vodka” under the sink at all times, for some stubborn things), and this is just that sort of cleaning.

Your dish soap is a hybrid molecule (a surfactant, specifically), and so will eventually break down the marker’s ink (promise!) but it’s not nearly so easy. I’ll be honest that I don’t know why this is. But because it’s not so easy, I don’t wait on dish soap.

Other notable things

It shouldn’t surprise you to know, the thing that makes beer fun is… alcohol¹. Which breaks down permanent marker. So, yes, some dribbles of beer can get you a situation like what you see in the glass below. I stuck my finger in the beer, then dragged it down my name to get this shot. Nothing more.

I want to mention a couple interesting things I discovered in working on this post regarding metallic Sharpie colors vs non-metallic colors. I found that silver doesn’t write on glass for love or money. I also found that the other two metallic colors, copper and gold, work wonderfully and show up fabulously on dark beer. The catch? Sometimes they are a right pain to get off. Not at all undoable, but hard. I don’t know what the difference is. You can see in the photo below, though, that the red and green letters came off FAST and the copper @ and the gold “cook” took much more work.

Finally, the oils on your hands will also slowly break down the marker. This is why I mention having to, on occasion, rewrite people’s names on the glasses above. Some folks have to rewrite more often than others. I have no idea if this is simply due to the way they hold the glass, body chemistry, or some other factor. But be aware of it.

And enjoy your next party in style, while impressing your friends with this little bit of “magic.”

Further reading, should you so desire, can be found at Wikipedia, as always, under Chemical Polarity.

¹ Notice I said “vodka” was a fine alcohol with which to remove the marker. ➥