Gold foil on a mockup is a metallic finish whose reflections follow a light source. It looks real when the light direction and the sheen match the scene it sits in.
Prepare the foil shape
Use the logo or monogram as the foil area. Any image works: Muckup turns it into a black-and-white mask.
Add the foil to the layer
Click the sparkles at the right of the layer and choose Gold, Silver or Copper, or hold ⌥ while dropping the shape on the layer.
Choose flat or raised
Flat foil reads as a hot-foil stamp. Raised foil adds depth. Add Sheen for a slight ripple that reflects the scene.
Match the light
Turn the light around the mockup and watch the reflections move, or click Match the Photo to align it with the scene.
Export
Export the mockup, or the whole project with the same light on every scene.
Silver, copper and blind effects
The same steps work for silver and copper. For a blind emboss or deboss with no ink, hide the print with the eye on the layer thumbnail and keep only the finish.