Rare glass onion bottle restored after 300 years

Two glass onion bottles that have survived under the waters off Florida’s Atlantic coast for 300 years have been successfully freed from their ocean crust and restored to their luster. Conservators at the Florida Department of Historic Resources’ Bureau of Archaeological Research Conservation Laboratory salvaged these rare 17th-century glass objects by removing a thick layer of nodules and reinforcing the fragile surface.

The bottles were recovered from shipwreck sites off the coast of Indian River County in 2021 and 2022. The specific ship cannot be identified, but it was part of the Spanish Plate Fleet of 1715, which transported gold, silver, gems, tobacco, chocolate, spices, and indigo from the New World colonies to Spain. Eleven ships of the fleet were destroyed by hurricanes off the coast of Florida.

Onion bottles are made using the free-blowing technique: glassblowers inflate molten glass through a blowpipe rather than using a mould. Each piece produced using this technique is unique in shape, size, thickness and weight. They were traded for their contents and utility items. On board the ship, these bottles may contain alcoholic beverages consumed by crew and passengers.

This type of bottle is fragile and rarely comes out intact. They’re usually broken up in shipwrecks, and if they do somehow make it to the ocean floor intact, they’ll be constantly roughed up by tidal forces. When they are impacted, they also become coated with sand, shells, and various other marine life. Over time, nodules and continued exposure to seawater can cause the glass surface to delaminate (i.e., pieces of glass flake off).

Administrators spent seven months clearing and stabilizing the fragile vessels.

After careful slow cleaning and drying, the bottle remained intact and then reinforced with Paraloid B-72, an acrylic resin-based hardener commonly used for glass and ceramic preservation. Applying a few coats stabilizes the remaining pieces of flying glass and gives the bottle a shiny look that you can see in the processed photo.

The newly restored onion jar is now available for display at a local museum through the Florida Department of Historic Resources’ Heritage Loan Program.