Dating antique milk bottles
The bottom of a bottle is usually the thickest part, retaining more temperature throughout the production line.Because the bottom is hotter, it is also more fluid and has a tendency to sag, forming a shape like a spinning top which makes it unstable on flat surfaces.
This is because there is little dating information to be gleaned from simply the base profile, though the profile can assist at times with the typing of a bottle.Simply put, this is the shape of the bottle base when viewed straight on and is usually the cross-section shape of the bottle body, though there are exceptions to the latter.Giving a bottle an arched shape at the bottom means that if it does sag, it can do so without touching the bottom.(British Glass 2004) In conjunction with the finish (lip), the various attributes and features found on the base of a bottle allows for some of the better opportunities for the manufacturing based dating of a bottle.
This potential for datable features is very useful since bottles are more often than not lacking embossing - an attribute which can often enhance dating opportunities.Also, shape is extremely variable and usually only loosely connected with age and function.