Superglue: Be careful with it!Superglue is awesome.

Originally discovered in 1942 by American scientists who were trying to come up with good transparent gun sights during WWII, superglue is the “sticks to everything” goto adhesive for all your gluey quick-fix needs.

And frankly, until you’ve superglued two fingers together, you really haven’t lived…

Anyway, there’s probably a lot about superglue that you’ve never heard before. So, read on, and then you can go impress your friends with your amazing knowledge of cyanoacrylate adhesives!

About superglue

First of all, superglue refers to various types of cyanoacrylate (CA) adhesives. There are quite a few different kinds for specific applications.

Superglue works by rapid polymerization in the presence of water – usually, humidity in the air. This trait also helps explain why superglue is so good at gluing people parts together, as the human body consists of a whole lot of water!

It also explains why that darn tube of superglue never lasts very long once it’s opened…

Keeping superglue fresh

You know how it goes: open new tube of superglue, use it once, and put the cap on carefully. One week later, you try to open the tube and find it’s all gluificated together – even if you made sure no glue was left in the applicator tip. So, you use a pin to poke a hole, etc.

In short, superglue only has a shelf life of about 12 months – if you’re lucky – for UNopened tubes. The minute you open it, humidity gets into the tube, and it starts slowly polymerizing inside. Once opened, you’ll be lucky if the tube lasts a month.

So, it’s pretty pointless to buy a big tube of superglue unless you’re going to use it all at once!!

You can extend the shelf life of superglue by storing it in the fridge. Cold temperatures will slow the “self-gluing” a bit. Or, stick it in the freezer… Just make sure to allow the glue to warm to room temperature before opening it and using it. Otherwise, you’ll get even more condensation inside the tube, and it will shorten the 30-day Already Opened Limit.

How to superglue stuff

Use thin layers.

The thicker the layer, the less likely the polymerization process will result in a good bond. That’s why the liquidy superglue always works better than the gel variety (also, the gel type has additives).

Obviously, try not to glue your own parts together. If you do, use acetone to dissolve even dried superglue.

Incidentally, always have some acetone on hand. It’s great for dissolving superglue, expandy foam, and removing stickum from just about anything. If it’s sticky, acetone will remove it.

What not to superglue…

Do not try to use superglue on cotton, wool, or leather. Using superglue on these natural materials will cause a potentially wild exothermic reaction. In normal people speak, that means heat – and possibly fire!

Granted, you need to use a lot of superglue to start a fire like this, but it’s still good to know… especially if you’re stranded on an island with only cotton balls, a crate of superglue, and a bunch of raw bacon.

Superglue also doesn’t work well on some other materials, especially glass. There are special superglues for glass, but in my experience they don’t work very well.

Generally, superglue seems to work best on more porous materials, but not so well on very smooth surfaces.

Plastics: If it’s ABS plastic, forget it. Usually, the type of plastic is printed somewhere on it, along with a recycling symbol – or not. Most everything is made of ABS plastic these days, which requires either a special glue, or plastic welding with a soldering iron. For other plastics, test if possible. Sometimes it works, sometimes it doesn’t…

Crazy uses of superglue

Fillers: You can use saw dust to fill cracks and crevices in wood, and then add some drops of superglue. You can also use baking soda + superglue to make a hard, glass-like material for filling. Another similar trick: bone dust + superglue! Check it out:

Note that at least with the baking soda  + superglue trick, the reaction releases a bit of heat… Nothing to be terribly concerned about, but FYI.

Arrows: Wanna know how they glue fletching to arrow shafts? Superglue!

Fingerprints: Heat some superglue, and the fumes produced will react with the water in the air and harden on fingerprints, making them visible. Probably don’t want to try this one at home, as the fumes are toxic and can irritate certain conditions like asthma.

Nuts and bolts: Insert bolt, screw nut on the end, tighten. Then put a drop or two of superglue between the nut and the threads. Ta-da! Note that this does not permanently bond the nut and bolt – you can still use a wrench and unscrew the nut. But it does act as a kind of chemical lock washer.

How strong is superglue?

Which reminds me…

When two surfaces are superglued together, the tensile strength is rather high. In other words, it’s hard to pull the two surfaces directly apart after they’re glued.

On the other hand, two superglued surfaces can be more easily separated by a shearing force. To illustrate:

Tensile vs Shear StressSo, if you superglue two objects together, you’ll have a hard time pulling them apart. But if you shear them apart (sideways), it will be much easier to break the superglue bond. This also explains why you can superglue a nut to a bolt, and still remove it later: because turning the nut on the bolt threads is effectively a shearing stress.

Underwater gluing?

Yes, sort of. There are a few gotchas…

Many people say superglue is water-resistant, whereas others classify it as “weak” in terms of water-resistant adhesives.

There are special superglues that are more water-resistant, which probably clears up some of the confusion: not all superglues are the same thing!

But for true underwater repairs, there are much better, special-purpose adhesives one can use.

Note that generally speaking, water and especially heat are the two enemies of the most common type of superglue. Even then, you really have to consider the application: just how water- and heat-proof a bond do you need? A bond at room temperature that gets wet sometimes is a much different application than a bond subjected to boiling water 12 hours a day…

Gluing wounds shut

Okay, this one you’ve probably heard about. BUT… It’s tricky. There are official medical superglues, and all of them are different than the superglue you can buy at the hardware store.

In short, you CAN superglue small wounds together with the regular stuff. It works.

Just be advised that there are many different types of superglue, and the medical ones are different for a reason. One reason is patents, I’m sure… But another reason is skin irritation.

Is superglue toxic?

With a name like “cyanoacrylate adhesive”, you might think, “Sounds like cyanide – EEK!”

Well, some superglues have been known to cause skin irritation – even chemical burns – for some people. Also, the fumes are nasty and can irritate conditions like asthma for some folks.

Personally, I don’t use superglue for items I’m going to eat or drink from. It just seems like good old fashioned common sense given that there isn’t a lot of agreement on toxicity issues. When I hear, “Further study is required”, I assume it’s a good idea NOT to ingest it or coat myself in it. 😉

Is it really permanent?

Yes and no.

If you superglue two objects together, under normal conditions they’ll stay stuck together for a loooong time.

For things like superglued fingers, it’s really not the horror it appears to be. Fact is, human skin cells are continually shedding and growing, so your fingers would naturally come unstuck as your skin replaces itself.

Removing superglue

That’s why the guy in the above photo won’t have to spend the rest of his life with an old cell phone, toothbrush, and ping pong ball stuck to his face.

Just don’t get superglue in your eyes! That’s bad, bad juju… Continually flush with water, and call the paramedics. This is one Superglued Parts case where you cannot treat it yourself.

Have some superglue tricks and tips? Share in the comments below!

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