Almost all of us own at least two outdoor plastic lawn chairs, more properly called resin chairs, if not a whole dining set. Most of us watch them get dirtier and dirtier every year, until we finally scrap them for something cleaner. Sitting out in the weather tends to somehow grind them into a grey mess which doesn't want to wash off very well.
In the photo you can see the grey mess next to a half painted one that was just as grey. One day I sat down to study what works and what doesn't work in trying to clean them. There are a number of special cleaners on the market and although I keep testing, only one of them worked well, called PatioClean but it was not a miracle worker either. Nothing works without a lot of elbow grease and PatioClean dissapeared from the shelves because people found it was easier to buy new inexpensive chairs rather than spend two hours a chair to clean them.
Don't use solvents to clean
First let me tell you that some nasty solvents can get down to clean resin when used together with steel wool. The solvent tends to soften the surface and the steel wool actually removes a layer of everything. But it is a nasty job and not really much faster than other less toxic methods.
Get the grime off first
The real starting point is a ScotchBright pad. Actually in this case although the real brand name ones last a bit longer, it is probably wise to go to the dollar store and buy a whole pile of the imitation nylon pads -- they don't last as long but we are going to throw them out rapidly anyway.
Surprisingly enough you should not start with any cleaners at all. Water down the furniture and attack it with wet nylon pads. At this first layer of work you are just wasting any of the special cleaning products. Much of that grey grime comes right off and in some cases, or some spots, it comes right down to clean. Keep rinsing and as soon as the pad isn't having an effect, change the pad. When a fresh pad isn't helping much, stop. If the chair still looks grey, that means that the resin itself has chemically changed on the surface, you are no longer trying to remove dirt but need to remove chemically discoloured resin.
Clean to the original colour, or paint
Now you have two choices: cutting down to the original colour and waxing -- or painting. The cleaning and waxing method is still a lot of work to get a really "new" chair out of the effort and until I find a really effective chemical cleaner for resin furniture, I would suggest attacking the chair with a power sprayer -- no elbow grease required! Painting is quicker, but paint wears off and sometimes peels. You can start to clean and then decide to paint -- as long as you totally rinse off any cleaner. But you cannot start to paint and then clean.
With a high pressure water spray, adding soap to the spray is really not necessary, and a lot easier on the grass. What you want to do is to actually remove a bit of the plastic that has become discoloured. The strayer will leave a bit of a rough surface. You might want to give it a light hand sanding just to smooth it out, and/or apply a wax. There used to be waxes for resin furniture but if you can't find them, use a car wax. The great advantage of all of this work is that you have a really nice feeling chair, the wax makes it silk like comfortable on bare skin, and you can repeat the process for years if you like. Don't wax it if you decide to paint it to either get it whiter, or to change the colour. If it is waxed and you want to paint, they sell "wax wash" in the paint stores, designed to remove wax from floors before refinishing.
If all that elbow grease is too much work for you, it is time to paint. Now that the easily removable layer of grime is gone, give it a light scribbing with TSP, throughly rinse and dry. There is a paint made specifically for plastic resin outdoor furniture called FUSION by Krylon and is easy to find in renovation centres. It comes in a wide variety of colours so you can really go design crazy if you care to.
Notice the handle on my spray can in the photo above. Once I discovered the CanGun1 spray can handle I will never wear out my finger, my thumb and all other things that I try to continue to push that little spray can button with. This is not only the best control system for all spray cans, but has the best leverage of all handles I have tested, goes on and off of the cans easily and securely. One important working tip is to slide the handle clip straight onto the can -- and then slide it straight off the can. If you try to force it up or down going on or off you can break it. Just push straight forward and it will not stress the mounting.
With this handle spray can painting is a joy, not a chore.
Paint where there is no wind and no direct sun. Painting on the lawn will save a lot of clean-up of overspray (you can mow it off!). The key to a smooth and lasting job is a lot of very thin layers of paint. Very thin layers appear at first to be fruitless as you can hardly notice the colour changing. The advantage of very thin layers is that they dry very quickly, don't sag and end up stronger than one coat thick layers.
Always be moving when you activate the spray and always be moving when you stop. If you swing back and fourth -- always stop straying before reaching the end and start spraying after starting to move in the back swing. Never spray with the can stopped as that is one of the primary sources of dripping or drooping paint, too much paint in one place.
Don't paint so closely as to be able to see a liquid accumulation of paint on the surface -- don't paint so far away as to allow the paint to dry before it hits the surface -- generally 6" from the surface and moving parallel to the surface so that your gun is always 6" away for an even spray. If your spray can gives out a flat rather than a round spray, always move as if that flat spray was a brush. To find out how your can sprays, spray a very short burst straight onto a piece of scrap -- it will draw your spray pattern.
Once the paint is dry for a day or two you can give it that slick feeling finish, and a bit of extra weather protection by applying the PatioClean Wax. Just remember that you will have to scrub off all the wax if you ever want to repaint.
You'll have to calculate what your cleaner or paint costs and what your elbow grease is worth when you think of choosing between restoring or replacing those outdoor chairs and tables. At least you now know that they can be salvaged.