My garden furniture is a good quality hardwood which was purchased and treated 2 years ago. After a couple of summer's use, I decided to give it a clean up and bought the restorer from Cuprinol. It was £12.99, so quite expensive but I was hoping to get rid of the "weathered" look. You will see from the picture on the front that it claims to turn the "weathered" grey look back to the original colour.
The product was extremely easy to use and does not have a noxious smell as many products do, it is a quick process - paint the gel formula on, work into the wood with an abrasive sponge and leave for no more than 15 minutes. Wash off.
Disappointingly, the furniture looked no different after I had used the product, I can only assume it was because the product had already been treated with a stain two years ago.
My advice - if you have an untreated "weathered" piece of furniture, give it a go as it is easy (although not cheap), but if your furniture is already treated with a stain or varnish, it won't be effective - even if it looks weathered in places.
Also, do a test patch and do not leave on for more than 15mins. I did this on my first test patch and the wood began to blister.
Removes grey wood to reveal new wood.