Complicated mixtures of organic substances with glassy or solid liquid properties. Resins that remain liquid after the leakage are called balsams, hot hard resins (the resins in the sense of the term) that harden in the air due to the leakage of substances. The mostly intensive and pleasant balsamic smell is caused by numerous essential oils, for example terpenes. Various resins such as myrrh were therefore used in ancient times to flavour wine. The most famous resinous wine is probably the Greek retsina. Most resins are found in coniferous woods. They are obtained from plant or animal materials or are produced artificially. They have the ability to polymerise.
Examples of resins of vegetable origin are gum arabic and starch, while those of animal origin are albumin (from protein), casein (from milk) and gelatine (from cartilage and bone). One of the synthetically produced resins is PVPP. Due to their adsorptive effect, special synthetic resins are used in winemaking for ion exchange. This is used, for example, in fining (removal of colour defects), filtration (removal of bacteria and yeasts), and for deacidification, acidification and removal of tartaric acid.