Resins, tar, glues and shellacs (derived from insects) are all used in the binding of other materials or as a protective coating. Tar is also used as a protective support material during manufacturing. For example, hot resin, tar or bitumen can be poured onto a wooden holder. Metal materials that are to be decorated are pressed into the hot liquid. After cooling, the wood older makes it easy to hold the decorative material, such as silver, during the embossing or engraving process. Similar to the lead, reheating the resign or tar liquifies it allowing the finished pieces to be removed from the holder. The prized characteristic of these materials are that they harden into a strong strong finish. Similar materials derived from plants and insects, such as sap, latex and mucilage are used for similar purposes but are not considered to be resins.
RESIN
PLANT
Many plants secrete material for protective purposes.
FOSSIL RESIN
Amber is fossil resign from coniferous and other tree species. It is as hard as stone and used mostly for decorative purposes. Subfossil resigns such as copal, kauri gum, dammar and similar resigns become tacky when touched with a solvent. These types are sometimes used as a binding material
INSECT RESIN
Shellac and lacquer are resins derived from insects.
OIL AND TAR RESIN
Pitch is derived from petroleum, coal tar, and some plants. The terms pitch and tar are generally equialent and used interchangably. Pitch may also be called biumen or asphalt. When derived from plants, it is considered a resin if the focus is on chemistry. For our purposes, pitch has an important as a support material for the decorative process in manufacturing. The dry heating of wood causes tar an pitch to drip away from wood. Pitch is also an important material for water proofing.