The basic materials and media from which an object is constructed.
How to record
Use a single term, without punctuation or capitalisation. Maintain a list of standard terms. Describe the medium and support of ‘2 dimensional’ works. Do not describe surface coatings (eg varnish on paintings) unless they are of special interest. Do not include brand names.
wood; tempered steel; canvas; ebony; oil
As many times as required for an object.