I love you because... Message in a Bottle Key Ring

Step 3 'Patina' the Letters

You could use a chemical oxidizing agent here, but it's much simpler and more accessible to just color in your letters with a black permanent maker. After you've thoroughly filled each letter in, use steel wool or a fine grit sanding sponge to sand off all the marker on the disc. Because they are recessed, the letters will remain darker, and now you also have a nice, industrial look to the disc!