Plastic furniture is everywhere---it is the garden furniture of our age. Unlike wood and metal furniture, plastic has been notoriously impossible to refinish, so otherwise acceptable pieces of furniture end up in landfills for no reason other than that they begin to look a bit "tired." Breakthroughs in paint technology are providing new products that will breathe new life into old plastic garden chairs and tables.
Add ammonia and detergent to a pail of water, and scrub your garden furniture well---particularly in crevices where dirt can accumulate. Rinse well; set in the sun until perfectly dry. Paint will not adhere to wet surfaces.
Look furniture over carefully for obvious scratches, and sand until not quite smooth. Continue sanding very lightly over the whole surface. You do not want it to be rough, but you do need to have some "tooth" for the paint to adhere. Paint will fill very light scratches.
Place old newspapers on the ground outside, and prop cardboard behind your garden furniture to catch over spray from paint. Wear a paint mask, safety goggles and disposable gloves. You may also want to wear old clothes or a paint smock.
Follow manufacturer's directions to spray paint and recoat furniture with paint especially formulated for plastic---both Krylon and Valspar (available in most paint and craft stores) make excellent products for this purpose. Usually 2 or 3 light coats, with drying times from 15 minutes to 1 hour between coats, are all you need, but be sure to buy enough to finish the job in one go as paint colours can vary from batch to batch. Allow to fully dry as recommended before using furniture.
Dispose of newspapers/cardboard, and gloves in trash. Use up the paint---on other projects if possible, otherwise follow hazardous waste disposal guidelines to get rid of unwanted leftover paint and cans. University of Missouri extension service says, "Never put liquid paint into the trash or pour it down the drain... Paint disposed of this way can contaminate our water resources and the environment."
Share leftover paint with local charity organisations whose budgets are often slim. They will appreciate the donation, and you will save a trip to the hazardous waste department.
Always paint in a well-ventilated area to avoid harmful fumes.