Dyeing: Buy material that is 100% solution dyed acrylic. This means that the dye is added to the fabric while it's still in a liquid state. The color is in the actual fibers, not printed on top of the fiber. This will ensure a brighter, longer-lasting color that won't bleach out in the sun.
Breathablilty: how quickly a material will dry when it's wet. The longer the water sits on fabric, the quicker mold and mildew will grow.
Water Repellent: Water repellent does not mean water-proof. But it does mean that liquids will bead up and not immediately soak into the fabric, giving you extra time to wipe up spills.
Protective Coatings: Many outdoor textiles are treated with an exterior "coat" of protection. Crypton, for example, offers a wide range of materials and products with proprietary technology that are resistant to odor, stains, mold, mildew and bacteria. Sunbrella, another well-known name in the outdoor textile world, sells their products through a wide range of stores like Pottery Barn.
Cleaning & Maintenance: Be sure to follow the manufacturers recommendation for cleaning outdoor materials. Usually a regular dusting or rinsing with cold water should take care of surface dirt and debris. Spot cleaning is also recommended for more stubborn stains. Sunbrella recommends applying 303 Fabric Guard after washing as the soap and water combination will remove some of the outer protective layers and will reduce the ability to repel water.
What's Inside Counts: Last but not least, be sure that the cushion filler is also designed for outdoor use; otherwise the cushions will mildew from the inside out. Look for a layered polyester material like these fillers from Cushion Source.
Making It Last: Buy performance material from a reputable source that gives clear instructions as to the performance expectations as well as maintenance. You will be happier with your outdoor cushions if you take the time to regularly clean them. In the off-season, be sure to store your cushions in a dry environment and away from the elements. This will ensure a much longer-lasting product.
Recommended Sources: Many companies like Crate and Barrel and West Elm offer pre-made cushions made with outdoor-appropriate materials. If you like DIY projects, source outdoor material from places like Ballard Designs, Joann Fabric and Craft Stores , Holly Hunt and Bella-Dura.
(Image: Pottery Barn)
(Re-edited from a post originally published 4.21.11 - CM)