Gold on silver


I’m sure this has been answered several times but I haven’t been
successful finding anything in the archives…

In the book “The Jeweler’s Directory of Decorative Finishes” there
are photos (page 49, Bangle Stack by Diana Porter) of a few silver
bangles that have words etched into them. The book states: “22k gold
has been applied to the areas that have been etched away to create a
glowing recess of words.”

My question is. What is the technique used to get the gold into the