We had this question about painting a kitchen item:
That was apparently closed and then reopened by the community after editing included a picture and (slightly) more clarifying language. I don't know if the edits were the specific reason for the reopen.
So, I'm wondering where we draw the line at "canvases", if we'll call them that. Many artists will paint things such as reclaimed wood, clothing, toys and dolls, rocks.
These different materials all have different considerations for what types of paints or sealants made be used on them, based on the material itself or its application.
In this question, the surface was immediately clear (plastic), and so was it's application (it needed to stand up to wear and cleaning like you would a kitchen appliance.) The edit only further emphasized this. So, I'm still a bit confused!
Aside from this painting question, we also have upcycling, which will most likely deal with similar issues: unconventional items using materials that may need special consideration.
Where do we draw the line on what's an acceptable work material or medium?