Final answer:
The word 'fastidious' is an adjective that describes the painter.
Step-by-step explanation:
The word 'fastidious' in the sentence is an adjective. An adjective is a word that describes or modifies a noun or pronoun. In this case, 'fastidious' describes the noun 'painter', indicating that the painter is very careful and meticulous.
Learn more about Parts of speech