Making art cannot be taught. What can be taught are techniques in artmaking; how to use certain media or tools effectively, the right kinds of supports (surfaces on which to paint or draw) depending on media, or procedures for optimal results. No one can be taught how to make art. Making art is an amalgamation (I daresay) of the understanding of the elements of art and the principles of design, facility with media and techniques, and most importantly having something to say. That latter condition is very important, otherwise the thing is simply decoration. As a consequence, good art is like a good poem with something worthwhile to say, articulated well.
A bottle decorated prettily is not art. I hazard to say that it is likely that those who present decorated bottles (pretty or not) as art have not bothered to study this art thing with any depth. Had they done so, they would understand that art speaks and a decorated bottle says nothing. Art may speak to its formal aspects or it may speak of something worldly or personal. It may speak with depth or superficialness. Nonetheless, it speaks. Art has a history of transformations. So, no objections to discarded materials being used in the making of art. Picasso and the bicycle handle and seat turned into a bull’s head is my favourite example of found things being elevated to art. Picasso explained that he found the two together in a jumble pile and immediately his mind made the transformation. He welded the two together and today the results continue to tickle the imagination. Who would have thought the thing that gave comfort to one’s bottom and the thing that gave stability when balanced on two wheels in a line could together yield the bull the matador may one day contend with in the bull ring? But Picasso was a lover of the sport and bulls reappear in his work.
