It has a nice bouncy feel, is very comfortable and stylish.
Use the normal Chinese or Korean innertubes you thought were made in the U.S.
They contain lots of lampblack and other stuff that makes them UV resistant and not slippery.
The highly elastic natural rubber innertubes common in some warm countries are great for spearguns and slingshots but will break if left in the sun. Those innertubes are often red in color.
The black chair seat seen in this picture has been used and abused for several years in a busy room. It's just now starting to break down a bit, but is still comfortable.
Here's what to do:
1) Get a whole bunch of similar-sized innertubes from your local friendly bike store.
2) Cut them at the valve and cut the valve stem off.
3) Weave them in your favorite chair caning pattern, stretching them tight.
4) When you get to the end of an innertube, tie another one to it with a square knot. Arrange for all the knots to be on the underside of the chair.
5) Sit and enjoy the extreme comfort.
6) Stand and be acclaimed by throngs for your fine chair. Can you say "wabi-sabi"?
This chair could also be the subject of a "turn a normal chair into a rocking chair" instructable, but the pictures are pretty self-explanatory. The rockers are barrel staves.
Step 1: The Underside
While we're thinking about undersides of things, how about the underside of chairness itself?
Is a chair something to sit on?
Or is something to sit on a chair?
This was a major difference between Plato and Aristotle.
Plato held that chairs were embodiments of the ideal of chairness, which had its own existence.
Aristotle held that the ideal of chairness was a generalization made by us based our experience of real chairs.