How does Glue work

Q. How does glue work
A. If you look at most surfaces through a microscope, you will find that they are not smooth. What an adhesive does is work to fill in the gaps and build a bridge between two surfaces. The adhesive must then harden, so that the bond stays together.

Q. What different types are there
A. There are three main types of adhesives; Water based, Solvent Based, Chemical curing

Q. What's the difference
A. Water based adhesives are made of natural or syntehtic polymers, mixed in water, and are used when one of more surface is porous
(e.g. wallpaper paste). They are slow to dry and will not stick non-porous materials like plastic. Water based adhesives are typically made of Water - Polymer - Thickener - Additives to improve strength - Biocide which stops them fading in strength with age.

Solvent based adhesives are a synthetic adhesive polymer mixed in solvent. They are used to stick non-porous surfaces and are fast drying.

Chemical curing adhesives involve creating a chemical reaction, and sometimes this involves the use of an additional ingredient as a 'hardener'. They are particularly powerful and are also fast bonding.

Q. And so they all stick one surface directly to another
A. No. There are two general types of bonding - direct and contact.In direct bonding the adhesive directly between two surfaces.
In contact bonding, you apply a layer of adhesive to each surface, and then the two layers of adhesive are put in contact to stick to each other.

Q. Superglue is new, but surely the process has been around a long time
A. Yes, as ever, the Ancient Egyptians and the Romans were the first to come up with practical adhesives. And even famous
Cabinet Makers like Chippendale used glue for their furniture.

Q. So the Romans used chemical reacting polymers then
A. No, they used ground animal bones, flour and water. The development of modern adhesives based on plastics were only developed this century.

Q. Plastics, metals.. what else
Skin - intentionaly as opposed to accidentally with superglue. Adhesives are now used to stick skin together after operations, making safer, smother joins and bypassing the long process for stitches to heal.

Q. Why doesn't Superglue stick to the tube
A. Here's why...