Making signs on a CNC is a fun process for hobbyists, and can be a great money-making service for professionals. Sign painting is a nice way to make those characters “pop” from the background, and ensure that your sign is noticed by passers-by. With sign painting, however, there can be challenges with paint bleeding. The process of carving the characters in the sign exposes end grain.
What do we as woodworkers know about end grain? It’s like a bunch of straws, open for business and waiting to suck up whatever moisture is available. So, when you spray the characters with paint, the end grain can wick up that paint, pulling it outside of the area that you had designed as a “paint zone”. When that happens, you will see noticeable streaks of paint projecting outside of your characters. Yuck!
The best way to avoid this is to satisfy the thirst of the end grain with something that won’t produce those nasty looking streaks. How can you satisfy the thirst when you are sign painting?
Seal the deal. By applying clear sealer as George shows in this video, you will fill the end grain and prevent the capillary action from sucking up paint later.
Two coats if needed. Applying a second coat is good and cheap insurance. Your only opportunity to add a second coat of sealer is immediately after applying the first coat, and you won’t know whether you need it until after the paint is applied. So, either practice on some scrap, or just go for it and add the second coat while you have the chance.