WordNet records no synonym and no antonym for art paper. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a high-quality paper (usually having a filler of china clay)
Synonyms, antonyms and the broader and narrower relations for art paper come from Princeton University’s WordNet. Full sources and licences.