The Wrong Paint

• Ordinary eggshell, satin, semi-gloss and gloss latex paint are fine for interior shelves that aren't forced to endure direct sunlight, rain and cold weather. These types of water-based paints won't prove resilient on exterior shelves. Though the finish may look attractive and durable at the outset, over time, significant fading and premature wear will begin to appear.
  
  

Acrylic Paint

• A quality exterior acrylic latex paint will prove more durable than ordinary latex paint. This particular type of paint will hold up against ultraviolet rays and harsh weather conditions. Unfortunately, it may not remain durable when subjected to duress. If the shelves are forced to hold heavy items, chipping and fading may occur.
  
  

Acrylic Enamel

• Acrylic enamel is well suited for exterior shelves. It can expand and contract in varying temperatures and will not fade when exposed to sunlight. It is also very glossy and hard. These characteristics allow it to endure abrasion and hold heavy items.
  
  

Primer

• If you apply any type of paint directly over bare exterior shelves, rapid paint failure will ensue. To prepare the shelves for adequate adhesion, apply a primer base. Acrylic primers are well suited for exterior wood shelves; however, the primer will not bond to exterior metallic shelves. Choose a rust-inhibiting metal-etching primer for metal shelves, or you'll have no chance at achieving strong paint adhesion.
  
  

Considerations

• If you use an acrylic enamel, you do not need to apply any sort of clear sealer. However, if you choose an acrylic paint, you can apply a clear polyurethane sealer to help protect the finish from premature wear. Ensure the sealer is water based, or cracking and poor adhesion may result.