The easiest thing to do is to repaint them with one of the new "for plastics" spray paints. I have used FUSION and I noticed that Lowe's/Home Depot are now carrying another brand that comes in tons of different colors. I'd just scrub off the dirt and repaint to cover the stains. The Fusion that I used on some chairs a couple of years ago has held up well.

I have seen spray bottles of strap cleaner in the stores. A patio store or even Home Dep. might have it. Frankly, I wipe my chairs down but I don't worry about what is under the straps. We're in a milder climate than yours and the set sits out year 'round.

Yo Ken, if your still around your up on this one. Far as Composites go I am with the Larry/whoever We are for the most part. Composites are really no longer using recycled material because there is just not enough of it so most of the raw stuff is virgin,the energy used to make composite is an enviro no no, when its time to remove the project composite is not real big on bio degrade its tricky to burn shreading it would be silly. Bottom line composites are not so enviro freindly. Info like that might suggest its not all that good to clean it either, with anything. I dont agree>> composites will out last Ipe, left to go silver/gray Ipe is as close to no maintance as a person can get. With the softer composites like Choice/MoistureShield even trex= tjunk I have found a coat or two of TWP 116 seals up the decking,locks in the color and keeps mold,mildew,stains from causing major problems. Of course not needing to do this is the reason the Wallet goes for composite in the first place. I my own self dont like composites at all for the reasons stated in several posts here and on other sites. Welcome aboard Larry!!! Sorry I dident understand your intent at the begining . John

Krylon also sells Fusion primer which I think is clear in color. Once you've sprayed your plastic with Krylon plastic primer, you can use any other spray paint over it. I LOVE Rustoleum Painter's Touch Ultra Cover spray paint. On the front of the can it says 2 x coverage. I like it because it comes in lots of lucious colors both satin and gloss. I just bought a can of satin finish "aubergine". What a GREAT color! And, it's about 1/2 the cost of Krylon Fusion. It definitely does 2 times the coverage...a can of it seems to last forever. I have had mixed luck with it over-wintering outside on plastic pots here in wet, cold, rainy Washington State, on the plastic pots I DIDN'T prime with Krylon plastic primer. Things I DID prime with Krylon primer did just fine, and are holding up well. Locally, Home Depot sells it for something like $3.25 per can, Joanne Fabrics sells some of the colors for $5+ per can. Lowes doesn't carry it.