My understanding of ketchup was that before they developed modern preservatives, a ring of crusty ketchup would develop at the top of the bottle (similiar to the crusty ketchup around the cap when it gets old and dries out) while the bottle sat on store shelves. In order to mask this crust, Heinz used a tall and thin bottle, because a smaller area will develop a less crust, and then they put a paper ring around it to hide it from view.
Welcome to the Straight Dope Message Boards, Barnable, we’re glad to have you with us.
When you start a thread, it’s helpful to other readers if you provide a link to the column in question. Yes, it currently appears on the front page as a “classic,” but in a few days time it will sink back into the Archives (it was written back in 1983.) So, a link helps keep us all on the same page, and saves searching time. Here’s what I presume you’re commenting on: http://www.straightdope.com/columns/read/172/why-are-ketchup-bottles-tall-and-thin-while-mustard-bottles-are-short-and-fat
No biggie, you’ll know for next time; and, as I say, welcome indeed!