Issue 46: Explanation about referring to use of materials in events and procedures

Techniques often imply the use of specific materials, or certain materials require respective techniques. When describing a production or modfication, the CRM gives preference to the documentation of the technique, which in turn implies the use of certain materials, e.g. "gold embroidery", "gilding". Not all materials are however captured directly by the technique, or the technique does not depend on more specific choices for the material, like the purity of the gold etc. If the technique is specific, i.e. a well defined plan or procedure, then material use can be documented as part of this procedure. It may be useful to have an additional property about the individual use of material in a production or modification. (see issue below). Materials actually embedded in an object are documented for the object directly. However, not all materials end up in the product, like solvents, detergents etc.