How to properly apply Bio-Cellulose sheet masks from Timeless Truth. Here we are using the Apple Stem Cell with Marine Collagen sheet mask, which helps to prevent premature ageing. Take out of the packet, and unfold the mask. Remove the paper backing, and apply the gel mask to the skin. Then remove the mesh cover from the top of the mask, and smooth over to ensure good contact with the skin. Leave on for 20 minutes for best results.