Water vs Solvent borne
Paints and varnishes are made up of 4 types of components: 

• Pigment
• Binder
• Solvent
• Additives

See article "What is Paint?" for details .

The binder may be dissolved in the solvent, as in a solvent-based gloss paint. The solvent may be an organic solvent or it may be water. Alternatively, the binder may be in the form of an emulsion suspended in water.

The terms solvent-based or water-based are not, strictly speaking, accurate. The coating is not `based’ on water or solvent, but is either dissolved or suspended in it. The terms `water borne’ and `solvent borne’ are more accurate descriptions.

Solvent-borne decorative paints tend to have a slower drying time than water-borne due to the nature of the binder. This is usually based on natural oils, such as soya bean oil, which reacts with the oxygen in the air to form a tough durable film.