Cobalt Blue Poison Bottles: How to Tell Old from Reproduction
Cobalt blue poison bottles are among the most collected pieces of pharmacy glass. They are also widely reproduced, so a few careful checks are worth making before you buy.
Why poison bottles were blue and ribbed
Cobalt oxide colours glass a deep blue. In the 19th century, laws in Britain and the United States began to require that poisons be labelled, and many makers supplied bottles in coloured glass, with ribbing, diamond patterns or embossed wording, so that a poison could be recognised by sight or by touch, even in the dark. Not every blue bottle held poison, and not every poison bottle is blue: green and amber examples exist too.
Read the seams and the lip
Look at the moulding seams. On many older bottles the seam stops at the neck and the lip was finished by hand. A seam that runs straight over the top of the lip points to machine production, which became common in the early 20th century. A hand-finished lip is a good sign, but it is not proof on its own.
Check the base
A rough, circular scar on the base (a pontil mark) is typical of earlier hand-finished glass. Look for honest wear too: fine scratches and scuffing around the base rim where the bottle has stood on shelves for decades. A base that looks perfect, with crisp edges and no wear, deserves a closer look.
Common signs of a reproduction
Be cautious of very uniform glass with no bubbles or ripples, an unusually bright and even colour, embossing that looks soft or blurred, and an "aged" finish that is the same everywhere. Ask the seller for photos of the base, the lip and a close-up of any embossing, and compare them with bottles in museum or auction archives.
Find examples on eBay
Browse cobalt blue poison bottles and embossed poison bottles on eBay, and use the photo checks above before you bid.
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More guides
- How to Identify and Date an Antique Apothecary BottleA practical checklist for reading an old pharmacy or medicine bottle: how it was made, its color, embossing, closure and condition, plus what to ask an eBay seller.