Fortunately for us wood workers and tinkerers, one of mankind’s most
indestructible substances — polystyrene — is easy to repurpose into glue.
And since several people have commented on my end grain end table project asking for the secret recipe to my homemade glue, I’m here to provide. However, I’m going to force you to read this entire thing before I get to the point, so bear with me.
I work a lot with polystyrene, partly because it can be found everywhere, but mainly because it is nearly indestructible by natural processes.
But before I get into the glue making (which is painfully easy and can be summed up in one line) I’ll tell you how to identify polystyrene.
1. Expanded polystyrene, also known as Styrofoam, can be found everywhere. If you need some, take a walk by a river or an unmaintained beach. It’s used as packing material for all that stuff that’s now falling apart, so it’s kind of like a repair kit included with your coffee pot.
2. Regular polystyrene is usually labeled with a “6” in that little recycle symbol that’s stamped into most plastics. Most of those plastics are clear food containers and the lids from fast food cups. If there is no number on the plastic, look for the letters PS. My experience suggests that glue made from solid polystyrene makes a stronger glue than the stuff made from foam.
So, to make glue, as promised, in one line:
Add polystyrene to acetone. The resulting goo is glue.
Now, the details:
Acetone is a naturalish chemical that can be found in paint stores and in fingernail polish remover. According to Wikipedia, it’s mostly harmless to both the environment and to people.
However, it’s super flammable, so don’t be a dumbass. But it does evaporate quickly, so it serves our purpose well.
Also, the bubbles coming off the polystyrene are air, nitrogen or whatever was used to inflate the foam. Still, this is a project probably best suited for the back porch.
Since acetone is used for most chemical processes, it will always be produced in significant amounts. A quart, which will make about a gallon of glue, will cost you about $10. Sorry about that. But this dissolved polystyrene is pretty cool stuff, and I think you’ll get a lot of use from it.
There is no real formula or mixing ratio for the glue. Once polystyrene dissolves in the acetone, it condenses at the bottom as a slimy awesomeness of sticky. It’s this stuff that works as glue.
Add glue wherever glue needs to be added. Clamp and let dry overnight. The glue will harden back into polystyrene, but embedded in the wood. The result is glue stronger than the wood it is holding together.
Don’t rule this out as a wood filler, either. It’s tough and can be dyed and painted. I think it could also be used as a finish, but I have never tried it and take no responsibility for ruining the hand carved velociraptor you’ve been working on. Also, please post the raptor photos.
Acetone will not dissolve:
2. PET bottles
However, plastics such as soda bottles are designed to use as little material as possible. So they tend to be susceptible to about anything. Really, you’re best using a glass jar with an airtight lid. I also think a plastic glue bottle would work, but I have never tried it. (EDIT 2-27-11: Yep… old glue bottles work perfectly!)
You’ll want to keep the glue in the acetone solution, as it will harden back into plastic if you allow it to dry. You can use a stick to dig out the goo and smear it on whatever you’re gluing (a light smear will suffice) or squeeze it out of the bottle like you would with regular woodworking glue. It is a bit thicker, so you may still have to smear it around some.
And that’s it. Thanks for reading!
EDIT 6/21/11: I finally had a chance to do some actual shear testing in the lab. The glue does fail before traditional carpenter’s glue, but has a holding force of about 750 PSI. The wood does not fail before the glue, unlike other glues. Maybe this would be a good material for temporary fastening, or something that would work for non-structural gluing. Your call. Thank you to everyone who read this!