I asked Chemist husband what kind of fumes the PVC might give off.  He thinks Hydrochloric Acid, I will definitely try this outside with a fan to be safe.  We painted PVC white pipes black to match our cutain once.  The man at the hardware store told us to sand it a little and prepare it with a special basecoat to help the blank paint stick.  It stayed on very well, but I don't remember the basecoat product we used, it was many years ago. For foam I spray with spray adhesive before spray paint and that keeps it from flaking off, maybe some adhesive basecoat would work on PVC to make paint stick better.

Thanks for that Snail. I mentioned the fumes in this vid as someone commented on another vid I did using PVC. I did not know what fumes it gives off so I thought I'd play it safe. It does smell just a little as it heats , but I do not find it offensive. When you think water pipes are PVC which you drink from, it should be  reasonably safe. I just did not know what it produces on heating. Hydrocloric acid is basically the acid in your stomach.. so I suppose this has the safety seal of approval. like silicone... the smell it gives of is acetic acid, or what is in vinegar, so it is pretty safe  also. Thanks for investigating for me.
   By the way, oil based paint flakes or scratches off; vinyl house paint sticks best. At least in my interior decorating days that is what we used to best effect...but in the long run, plastic being plastic, not  much sticks for the long haul.

They make a spray paint for plastic. It might work for PVC , It seems to hold well on plastic  out door furniture.

Julie - maybe H.L., but haven't seen them. If they have them it will be by the Science fair project stuff.  Anywhere that sells stuff for Science fairs should have them.

Shawn, I said I would try doing a white PVC eyeball, so I did. White works well. Pressing other PVC into it  for iris and pupil does not work.The PVC does not 'give' enough, and does not stick. You can glue with plumbers PVC cement though so in the following photos you can see that, Iris stuck on. It was molded though to make it sit  flat. The pupil I 'inserted' by drilling a hole in the iris cutting a darker circle , heating the dark disk, then pressuring it into the hole to make a snug fit, then sanding it flush. It will polish up sort of OK as much as PVC will.

   

Looks cool. I love the colour of the iris, too!

Doesn't look to bad. I wonder if painting it with clear gloss would work to give it some shine?

Rika, yes it is a nice color, but if you use just pvc for your colors, you will be limited to green, orange, yellow, white and dark grey, as those are the standard colors that pipes and things come out in, at least here anyways. Painting would then be in order, or use another material for the iris. But the white works for the base eyeball at least. And yes I suppose Shawn that painting and laquering would do.  I did not buff the eye up to its maximum gloss by the way. You could also try  furniture polish to give it an extra sheen.I personally will not be using the eyeball shiney like that for a couple reasons, although some may do so.
   First is attatchment. They would have to be glued on, and gluing is not the best with camerawork unless your character is a short term one off, as gluing eyes and features always come off eventually. They don't last a series. Sewing is always better.I may come up with a system to get them to stay on that would be better than gluing, but we are not there yet.
   Second, Shiney eyes can look cool, but on camera if they are too shiny, they can 'glint' and sparkle, which can be distracting. So up until now I have used cloth coverings. We have had problems in the past with shiny  glasses, and you have to adjust lighting sometimes to redirect reflections. I must give fingernail polish a try for  coloring to see how well it  sticks to PVC, and also try inserting the iris, so that it does not stand out so much.

To attach these, since you are already drilling a hole to create the iris why not extend that through the white of the eye. Then use a bolt as your pupil. It goes down through the iris then through the white eye ball. Put a nut on to tighten this all down. If you get a long enough bolt then you can have an attachment to the head much like the commercial eyes. Simply poke the bolt through the fabric and foam then put a washer over bolt then a nut to tighten down. When I started composing this reply I was thinking that the slot in the bolt would have to be filled in somehow but duh.... carriage bolts are not slotted.    http://www.google.com/search?q=carriage+bolt

I know it's the simplistic easy way out but my vent puppets have googly eyes and the couple hand puppets I've made I have used them too.  Cheep at the dollar store and they move around.  They started making some more advanced ones shaped like real eyes but I have only seen Small ones.

Interesting Shawn. I was thinking maybe trying a round PVC plug glued into the back side of the eye, with a bolt through before gluing it... or sewing the  plug like a button, to the head first, then gluing the half sphere eyeball onto the PVC plug(with plumbers PVC glue). The PVC plug would need to be a snug fit, but I can see it working.