I have 4 plastic resin chairs that I've had forever. They are very sturdy chairs yet I couldn't sit in them because after years of sitting in the sun every time you touched them you came away with green powdery stuff all over you.
I don't knew where I saw it but I came across an idea to use one of these to restore the chairs
I figured I had nothing to lose if it didn't work because these weren't getting used any way. I didn't do the best job on these but all you do is run the torch back and forth across the surface as if you were spray painting
The chair on the left is the after and the one on the right is before I did anything to it. I should have scrubbed all the dirt off better before I did this but I have to say that it made a huge difference. We can actually sit in these chairs again. The second one I did I did a little bit better job on.