I have been an Antique dealer and appraiser for 32 years now and many people have asked me where they can go and get classes to become an appraiser or help them be a better collector. While there are some colleges with courses, they are few and far between. When I first started there were no courses and darn few reference books of any kind. Instead I learned by collecting and by talking to advanced collectors and dealers, who loved antiques like I did. These people were willing to share their hard gained knowledge with me just because of that mutual love of antiques.
So part of the reason for this blog is to pay them back by sharing some of my knowledge with others like they did. I want to reach people who care about antiques to share more than just the mechanics of identifying old from new, or how to value something. I also have selfish motives for doing this. I think the more people know about antiques the better they will be as customers, and it will help keep the whole antiques and collectibles market healthy.
Antique Glass Basics
We have evidence of antique glass beads in Egyptian tombs going back to 4500 BC. The basic formula for glass is silica sand and heat. If you have a big enough bonfire on a beach you can melt some of the sand and turn it to glass. That is probably what gave the idea to the first glass makers. The problem is it takes a lot of heat, about 2400 F. So glass making required a kiln or furnace to be able to reach high enough heat to be practical.
By Roman Times, there was glass manufacturing all over the world with several areas mass producing everything from bottles to decorative items. Glass tended to be high-end, like perfume bottles, while pottery filled the low end needs like food storage. The early Egyptian glass pieces were just lumps of glass that were hollowed out or worked by chipping or abrasion similar to how natural rock was used.
Eventually blowing glass into a shape was invented and improved over time. To blow glass a metal hollow tube gets a “gather” of molten glass on one end out of the furnace. Air pressure from a man blowing into the tube causes an air bubble to form in the center of the gather and by turning the tube and continued blowing the bubble grows and a hollow vessel is formed. Continued heating and manipulation with wet wood paddles, and other tools allows this hollow object to be shaped. It is broken off the blow pipe and cooled or it is attached to a metal “pontil” rod by a small bit of molten glass for additional shaping.
Free blowing and shaping was time consuming to learn and it took years of practice to become a master blower. This was fine for luxury items but for mass production this was a problem. To speed things up, molds were made and the glass was mouth blown into them. This took far less training and experience and thus was faster and cheaper and allowed the first type of mass production of glass items. By the 1820’s mold blowing machines were in use, which lasted until the 1840’s when mechanically pressed glass machines started to replace them.
This basic information helps when you are trying to identify what type of glass you have:
* Hand blown glass will show some variations in thickness and shape.
* It will usually have a pontil mark if it was shaped after initial blowing.
* The left over glass from the pontil rod is broken off and can be left rough, ground smooth or reheated so rough/sharp edges are round.
* All or most all American and English antique blown glass have ground pontils, mid to low priced continental European glass was more likely to be left rough or fire treated.
* Mouth mold blown glass (oldest) will have mold marks up the sides, though tops and lips tend to have hand shaping that obscures the marks.
* Look for more variations in pattern and thickness than machine mold blown pieces.
* Also look for “whittle” marks on the glass, these are streaky lines in the glass, (slightly indented) that are caused by a cold/wet mold quickly cooling the hot glass.
* Machine blown glass usually has 3 or 4 mold seams and a ground pontil on the base.
* Pieces with 2 mold marks tend to be pressed glass or late machine blown pieces.