Expert: Martin G Roberts - 4/19/2008

Question
I have found various explanations of the original purpose of the glass base of many pewter tankards.Some claim that the transparent glass allowed the drinker to keep an eye open for some possible threat, of which various examples are given; indeed a variant of this was the 'explanation' that  I was given when I was young. Such, however, seem always to be based on hearsay rather than on any substantive evidence. On the other hand there is the suggestion that the drinker was thereby enabled to spot the coin which the antecedents of the later press-gang might drop into the tankard, failure to remove which would mean that the unsuspecting drinker had been drawn into military service.
Can you cast any light on this please?

Answer
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English glass-bottomed pewter mugs began to appear in the late 18th Century (examples from that period are very scarce), and became commonplace during the 19th Century. They are still in production, as giftware items.

You are right about the numerous theories, though I'm not sure why you invoke 'antecedents' of the press-gang - impressment was an established practice in the 18th Century.

The majority of theories are fanciful, including the King's shilling/impressment.

Frankly, it is not clear what practical purpose a glass bottom was perceived to have. Making a glass bottomed mug is more complex, and therefore more expensive, than making one with a pewter base. One possible explanation is that it perhaps enabled the drinker to judge the clarity of the ale, but that is not especially convincing. Further, glass bottoms tend to break quite easily - many are now seen with cracked or broken bases - which undermines one of the benefits of using pewter mugs to serve drinks.

One observation is that, while pewter bottomed mugs often bear capacity verification marks and inscriptions that indicate their use in taverns, relatively few glass-bottomed mugs bear such markings. More often they have ownership inscriptions implying either domestic ownership, or institutional functions. The latter is exemplified by the commonly seen glass-bottomed dome-lidded tankards that were widely used as sports trophies (especially rowing trophies) in the mid to late 19th Century - examples from public schools and university colleges are fairly common.

So, the answer is that there is no generally accepted explanation - no conclusive research has been published.

Martin
www.antique-metalware.co.uk