Resins when separated and purified are often hard transparent or translucent hard, brittle solids or slightly soft semi-solids. They are heavier than water and by the action of heat they soften and fuse, yielding clear, adhesive fluids. Specific gravity of resins varies from 0.9–1.25. They are usually transparent when pure and become opaque when water is present. They burn with a characteristic smoky flame. Resins are insoluble in water and rarely soluble in light petroleum and more or less soluble in alcohol, ether, acetone, chloroform, carbon disulphide, chloral hydrate solution, fixed oils, and volatile oils. On evaporation, solutions of resins deposit a varnish-like thin film.

Chemically, resins are constituted of a complex mixture of resin acids, resin alcohols, resin phenols, esters, and inert resins The element nitrogen is not included in the composition of resin components.

Resin acids (abietic acid in colophony, commiphoric acid in myrrh) represent a large proportion of diterpenoid oxyacids, combining the properties of carboxylic acids and phenols. They occur both in the free state and as esters. They are soluble in aqueous solutions of alkalis forming soap-like solutions or colloidal suspensions. Their metallic salts are called resonates and these are extensively used in the manufacture of soaps and varnishes.

Resin alcohols or resinols (benzoresinol in benzoin, storesinol in storax) occur in the free state or as esters in combination with simple aromatic acids such as benzoic, salicylic, cinnamon, and umbellic acids. Complex molecules of high molecular weight called resinotannols (siaresinotannol in benzoin, peruresinotannol in balsam of tolu) precipitate ferric salts similar to tannins.

Resenes are complex neutral substances without characteristic chemical properties. They do not form salts or esters and are insoluble in and resist hydrolysis by alkalies.

Depending on the predominance of constituents, resins may be classed as acid resins (Colophony, Guaiacum), ester resins (Benzoin, Burgundy), or mixed resins (Mastich, Shellac).