Blake wrote his Descriptive Catalogue in 1809 in conjunction with his exhibit of his works in his brother James' home. He explains here why he choose not to paint in oils but chose tempera or watercolor instead.
Descriptive Catalogue, (E 530)
"CLEARNESS and precision have been the chief objects in painting
these Pictures. Clear colours unmudded by oil, and firm and
determinate lineaments unbroken by shadows, which ought to
display and not to hide form, as is the practice of the latter
Schools of Italy and Flanders"
One of Blake's temperas, a dramatic scene from the Garden of Eden is in the collection of the Victoria and Albert Museum. Eve must have been as brave as she was beautiful and gullible to accept any gift from Blake's serpent. The sleeping Adam recalls to mind the sleeping Albion of Jerusalem. Look for symbols of the fall, materiality, dominon by the feminine and mystery.
Victoria and Albert MuseumGenesis 3
 Now the serpent was more subtil than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?
 And the woman said unto the serpent, We may eat of the fruit of the trees of the garden:
 But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die.
 And the serpent said unto the woman, Ye shall not surely die:
 For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.
 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
 And the eyes of them both were opened, and they knew that they were naked; and they sewed fig leaves together, and made themselves aprons.