Do you know what makes a gluey substance
stick to something else?
You may be surprised to hear that there’s no single, simple answer—but that’s not so surprising if you consider how many different types of glue there are and how many different ways in which we can use them.
Here are four theories of how things can stick.
1) Adsorption is a surface sticking effect caused by small, attractive forces between the adhesive (yellow in graphic) and the substances it’s sticking (red and blue).
2) Chemisorption involves chemical bonds forming between the adhesive (orange in graphic) and the substances it’s sticking together.
3) Diffusion sticks two things together when molecules cross the boundaries from one into the other and vice-versa.
4) Mechanical adhesion happens when a glue (green in graphic) fills the space between two substances and the cracks inside them, creating a strong physical bond.