Do you know why antique bottles turn purple? It’s a question that many people have, and the answer is actually quite interesting. Contrary to popular belief, the color isn’t caused by mold or age. In fact, it has nothing to do with the bottle itself! The secret lies in the glass used to make the bottle. Keep reading to find out more about why antique bottles turn purple and how you can prevent it from happening to your own collection.

Why do antique bottles turn purple?

The reason why antique bottles turn purple has to do with the way that light interacts with the glass. Manganese was commonly added to glass during the production process in order to make it clearer and more durable. 

However, over time, exposure to sunlight causes the manganese to break down. This reaction manifests as a purple hue on the surface of the glass.

When did they stop putting manganese in glass?

Manganese was a common additive in glassmaking until the early 20th century. It’s what gives antique bottles their characteristic purple hue. 

However, manganese is also quite reactive and can cause problems in the manufacturing process. 

As a result, it was eventually replaced with other materials. Today, you’re unlikely to find manganese in glass except in antique bottles.

How long does it take glass to turn purple?

This depends on the amount of Manganese present in the glass and the level of exposure to sunlight. In general, it takes several years for the reaction to occur. However, if the bottle is kept in a sunny spot, the process can happen much faster.

Is purple glass valuable?

The value of purple glass depends on a number of factors, including the age of the piece and its condition. Generally speaking, antique bottles are more valuable than modern ones.

 However, there are some exceptions to this rule. 

If you’re unsure about the value of your purple glass, it’s best to consult an expert.

Purple Glass in the Middle Ages

Purple glass was a rare commodity in the medieval times. It was only made in the Middle Ages and it was expensive.

During the medieval time, purple glass was a rare commodity. It was not made during any other period of time and it was very expensive. 

Purple glass was made by heating the lime and sand mixture with a third of its volume of potassium or sodium carbonate solution. 

The glaze on the surface was made by adding antimony sulfide or lead sulfide, both of which have high melting points.


As you can see, there’s a lot more to why antique bottles turn purple than meets the eye. Now that you know the secret, you can enjoy your collection with new appreciation! And if you ever find yourself with a purple bottle of your own, you’ll know just how special it is. 

I hope you enjoyed this post. If you have any questions or comments, please feel free to leave them below. I’ll be happy to answer them as best I can. And if you’re interested in learning more about antiques, check out our other blog posts.

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