Therr are many types of glue including: PVA, gluesticks, super glue, etc. Im wondering, why some are better than others and why some glues don’t work at all? The typical school glue stick can sometimes barely glue a sheet of paper to another while some glues can stick buildings together.
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Adam Savage did a lovely section on this in Every Tools a Hammer.
To answer you’re question though, different glues work differently, but at the base mechanics for most glues, we have something that is either “wet” and has a lot of long spindly things, think jelly fish. When these “dry” those long spindly things tighten up and grab things.
This certainly applies to pva, wood glue, and super glue.
This also sort of applies to epoxies, just instead of drying, one of the ingredients makes the long bits shrink down and grab stuff.
For why some are “absolutely horrible” theres different needs for glues, for your example, it would be terrible to use construction adhesive on craft paper, school glue sticks are nice because after they dry, the glue remains flexible. Meanwhile, super glue has basically no flexibility upon curing, and epoxies can be hit or miss.
Also note, some glues spindly bits simply don’t grab onto certain materials, or they don’t really grab onto each other.
Different kinds of glues stick things together in different ways. A lot of them (like Elmer’s glue or wood glue) seep into tiny holes in each material. When they dry, the two items are bonded together by the glue.
Others work by chemically bonding the two surfaces, or in a similar method to Elmer’s, but using a two-part epoxy to harden the bond, rather than drying.
Glue can work a couple different ways. In most cases it’s a non-solid material that hardens between the two objects you want glued together, and before hardening it seeps into all the little pores and holes of the material. This is mechanical adhesion.
Some glue is especially effective on certain materials, for example, wood glue is way better on wood than on plastic. This is because wood glue is made with the chemical structures of wood in mind in order to bond at a greater level. This is dispersive adhesion.
Some glues will take dispersive adhesion to the next level by chemically reacting with a material in order to create hydrogen bonds – a particularly strong chemical reaction – to stay bonded. Ever gotten gorilla glue on your hand and had to remove it, and your skin felt super soft afterwards? That’s because it bonded to the top layer of your skin and you had to rip that top layer off to get rid of the glue.
As for the efficiency of the glue, school grade glue sticks are made with a lot of filler and shitty cheap material, so it’s not going to work as well as a wood glue or industrial grade adhesive.
Different types of glues.
Some glues harden and simply bind.
Some glues stick to a surface.
Some glues chemically alter the surface and bind to it.
Se glues melt things and fuse them together.
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By altering the composition or chemicals in the glue, you can make it more or less sticky. More or less flexible, or brittle and breakable.
So many different types. A terrible glue is just an incorrect choice.
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