diff --git a/js/moleculesandlight/view/ObservationWindow.js b/js/moleculesandlight/view/ObservationWindow.js
index 9d86f21c..75a25535 100644
--- a/js/moleculesandlight/view/ObservationWindow.js
+++ b/js/moleculesandlight/view/ObservationWindow.js
@@ -103,7 +103,6 @@ define( function( require ) {
     this.returnMoleculeButtonNode = new RectangularPushButton( {
       content: buttonContent,
       baseColor: 'rgb(247, 151, 34)',
-      opacity: 0.99,
       touchAreaXDilation: 7,
       touchAreaYDilation: 7,
       listener: function() {