What a great question! Another example of something that just "is"
until we think to question.
Despite the fact that your question appears on email forwards like
"The Authoritative Unanswerable Questions"
< http://www.jimpoz.com/jokes/authoritativeQuestions.html >, there
really is a solid explanation. Margo Lloyd of Bell Carter Foods,
quoted in the Cincinatti Enquirer, states it succinctly:
?Black olives, technically known as black ripe olives, come in a can
because we actually cook them in the can. Olives go in, a brine or
juice is added, cans are sealed and they then go into a continuous
cooker. Glass simply can't hold up to the intensity of the cooking
Green olives, meanwhile, are processed differently ? they're
pasteurized but not cooked, then put in jars with brine added."
"Green olives in jars for a good reason" by Jim Knippenberg
< http://www.enquirer.com/editions/2001/06/25/tem_ask_a_stupid.html >
For further evidence that you're not the first to question this
practice, check out this thread on AskEarth.com, where members engage
in speculation on this very topic:
< http://askearth.com/go/view_request?request=108885 >
Finally, you may enjoy this olive info clearinghouse:
An ode to olives - olive lovers unite
< http://www.emeraldworld.net/olive.html >
I used the following search combinations to answer your question:
olives jar versus can
how olives made processed
reason olives sold in cans
Please let me know if you require clarification. All the best!