If the rug pad was marketed not to stain floors, then you need to bring your concerns to the manufacturer of the pad. Unfortunately, a good deal of what is offered for sale here in America comes from you know where, so your chances of getting the rug manufacturer to own up to this damage is remote. Perhaps the store where you purchased it may help? This kind of staining, whether it occurs on vinyl flooring or in your case your wood floor, is usually due to the rubber content in the backing chemically changing the surface of the flooring resulting in the stain you see. These stains usually fade when exposed to air and light, but that is not always the case.

I have never had a problem with the rubber waffle type pads ruining my wood floors. Rubber on vinyl will discolor the flooring. You can buy fabric backed rugs and since it will not be in a traffic area you won't need to worry about it slipping but it will not scratch the floor. If you get one with a rough back I would still use something under it because it will slide when you move the table for your laptop use and then you will end up with scratching the floor eventually.

graywings, I gotta tell you, I don't see how you were able to fit a 5 x 7.5 polypropylene rug in your washer, or any washer known to man for that matter. Maybe if I cut it into quarters? Not even then. You know when a few towels or throws can cause the washer to get off balance and rock? This would have caused some catastrophic bomb-worthy event. I washed it yesterday. First I hit it with the jet setting on my hose. I used a lot of water. It wasn't even wet underneath!!!! So more water. Then I used Scrubbing Bubbles (green cap) and an iron brush. Then plenty of rinsing. Finally it was completely saturated. I had planned to put it on 4 sawhorses to dry. That little 5x7.5 rug was so heavy with water that it couldn't be lifted. Not remotely. It had become THE THING!!! I managed to wiggle the flattened sawhorses underneath so it would be slightly elevated off the patio tile. Yesterday was sunny, warm and windy. I figured it was a good day for drying. Hah!! This morning I could tell some water was gone because it was slightly easier to move. I managed to get it on the standing sawhorses and water started seeping out. This is gonna take days. It has to be absolutely pristinely dry before I'll put it on my hardwood floor. Lesson: I will not do this again, at least not with a polypropylene rug that holds water like a sponge. So glad I didn't try this with my 10x13 rug. Ouch!!! After I moved the table and chairs and before I took it outside, I took a Before photo. It actually looked pretty good. I didn't see any dirt or grime come out. I suspect that rug was a lot cleaner than I'd imagined.

Natural rubber will most likely stain the surface. I have not heard of PVC doing that, but with all the crap that comes to us by way of China, I would not be surprised. The best nonstaining rug pad option I found was those manufactured under the name WunderGrip out of New Jersey.