What causes my white outdoor furniture to leave white chalky marks on my clothing when I sit on it? How do I get it to stop?
Janis from Corpus Christi, TX
Although all paints will chalk over time, some types have a tendency to chalk sooner. oil base paint, oxidize faster than most acrylic and latex paints. In most cases, an acrylic paint is a better choice for exterior painting.
Another aspect is the quality of the paint. A general rule is "the more expensive the paint the more and better the resins it has". The resins are the binders that hold the pigment. When they degrade the pigment is at the surface and appears chalky.
Cheaper paints will degrade faster. An example is exterior 100% acrylic paint verses a latex paint (or acrylic/latex combo paint). The best exterior paints on the market are 100% acrylic, not late.
Removing the Chalky Residue
This powdery residue must be removed and possibly primed before applying any finish paint. The rules are very simple.
To remove the residue use a pressure washer and mild, environmentally friendly, soap. Most pressure washers have the ability to dispense cleaners while washing. Use proper pressure washing techniques. Allow the soap to sit on the surface for 10-15 minutes then rinse completely. Repeat the rinsing until all soap residue is gone. Keep the pressure at 1500-2000 psi.
Allow the surface to dry completely, usually 12-24 hours. If the amount of chalking paint was excessive or a lot of residue still remains on the surface you will need to apply a quality primer that is appropriate for your application. In most cases an acrylic primer will be a better choice with a severally chalky surface.
Don't be overly concerned if a little residue is still on the surface. Chances are some will remain, even if you physically scrub your entire house.
My grandmother has green plastic lawn chairs that she has been having the same troubles out of; we had to spend the summer sitting on towels. We finally purchased some spray paint that is especially made for plastic and it worked wonders. It's been over a month and there has been no peeling or cracking. You didn't mention if yours are plastic or metal...I've seen a similar happening with metal. They also make the paint for outdoor metal too though.