how can I put an antique wash on an acrylic painting?

Answer 1

You'd be best to use one of the transparent earth tones such as Raw Sienna, Transparent Brown Oxide or Transparent Gold Oxide. Check the label to see if the colour is transparent so you won't lose any details in the painting beneath.

Add a bit to some polymer gloss medium (do not thin the paint with water!) mix it well to avoid streaks, and apply in broad strokes. Better to use a few coats of thin colour than one thick one. Let the layers dry well between coats.

Good luck