Dating old gin bottles
The presence of iron oxides imparts this dark coloration.
Early American glass blowers were from the European continent and brought with them this technology which had been used since at least the early 1600s.
The square cross section design of a case gin allowed for the efficient packing and transportation of these bottles in wooden cases, each containing from 4 to 24 bottles.
The dark color was desirable to help protect the contents from sunlight and spoilage and was a result of the impurities in the sand used to make the glass.
The molten glass was then flared out, rolled over and finished by flattening the top with a wooden paddle.
This technique was in common use from the late 1700s until the mid 1800s and indicates that this month's sea glass shard is at least 150 years old and possibly older than 200 years.
MOST VALUABLE BOTTLES The Most valuable Black glass bottles are those from the earliest period.
The form was called the shaft and globe so named for the bottle shape.