How did William Blake combine text and illustrations on a single etched plate?

William Blake combined text and illustrations on a single etched plate through a unique process he called "Illuminated Printing".1

To achieve this, Blake drew his poems and their accompanying designs directly onto a copper plate using a liquid that was impervious to acid. Once the design was drawn, he etched the plate with acid. Because the areas protected by the acid-resistant liquid remained, the design was left in relief, allowing it to be surface-printed.123

This method of relief etching enabled Blake to function as his own compositor and printer, integrating his handwritten text and artistic illustrations into a single, cohesive printed work. He used this technique for many of his major poetical works, including Songs of Innocence and Jerusalem.312