Illusion Glasses
Not all antique drinking glasses were made in the spirit of generous hospitality. The deceptive glass — also known as the illusion glass — was designed with a rather different purpose: to deceive the eye, confound the guest, and provide its owner with a quiet advantage at the table. These ingenious objects, produced from the late 17th century onwards, are among the most charming and characterful pieces in English glass collecting, combining fine craftsmanship with a very human sense of mischief.
What Is a Deceptive Glass?
A deceptive or illusion glass is a drinking vessel that appears, to the casual observer, to be a full-sized glass of normal capacity. In reality, the bowl contains an exceptionally thick base — a solid plug of glass that rises almost to the rim of the bowl — leaving only a small cavity at the top capable of holding liquid. Where a standard wine glass of the period might hold four or five fluid ounces, a deceptive glass of the same apparent size may hold only half an ounce or less.
The deception is effective because the thick base is the same colour and clarity as the rest of the glass. When the glass is empty, the solid base is visible on close inspection, but when filled with wine or another liquid, the refractive properties of both the glass and the liquid combine to make the base almost invisible. The glass appears full; it contains almost nothing.
How They Were Used
The uses of deceptive glasses were several, and not all of them entirely respectable.
The most commonly cited use is as a host's advantage: a host who wished to appear to drink generously with his guests while actually consuming very little could use a deceptive glass to maintain the appearance of participation without the reality. This was particularly useful in an era when the pressure to match one's guests drink for drink was considerable, and when the consequences of failing to do so — social embarrassment, loss of face — were taken seriously.
Conversely, a deceptive glass could be used as a practical joke: a guest offered what appeared to be a full glass of wine would find, on attempting to drink, that the glass was effectively empty after a single sip. The humour was presumably more appreciated by the host than the guest.
There is also evidence that deceptive glasses were used in tavern settings, where an unscrupulous landlord might serve a paying customer from a deceptive glass, charging for a full measure while delivering a fraction of one. Whether this was a widespread practice or an occasional abuse is difficult to establish, but the possibility was certainly understood at the time.
Construction and Identification
The construction of a deceptive glass requires considerable skill. The solid base must be formed as an integral part of the bowl — not a separate insert — and must be worked to appear as a natural continuation of the bowl's form. The junction between the solid base and the hollow upper portion of the bowl must be smooth and invisible, or the deception fails.
How to Identify a Deceptive Glass
Identifying a deceptive glass is straightforward once you know what to look for:
- Weight — a deceptive glass is noticeably heavier than a standard glass of the same apparent size, due to the solid glass base filling most of the bowl.
- The base of the bowl — looking down into the bowl, the base appears unusually high — much closer to the rim than would be expected. The cavity is shallow and narrow.
- Transmitted light — holding the glass up to a light source and looking through the bowl from the side reveals the solid base clearly, appearing as a dense, opaque mass within the lower portion of the bowl.
- Tapping — tapping the bowl gently produces a duller, less resonant sound than a hollow bowl of the same size, due to the mass of solid glass within.
Stem and Foot Forms
Deceptive glasses are found with a range of stem types consistent with their period of production — plain stems, air twist stems, opaque twist stems, and faceted stems are all encountered. The foot is typically of standard form and weight, since the deception is contained entirely within the bowl. This means that a deceptive glass, examined from below, may appear entirely normal — it is only when the bowl is examined directly that the illusion becomes apparent.
Dating and Period
Deceptive glasses were produced throughout the 18th century and into the early 19th century. The earliest examples date from the late 17th century, coinciding with the establishment of the English lead glass tradition following Ravenscroft's innovations of the 1670s. Lead glass, with its superior clarity and refractive properties, was particularly well suited to the deceptive glass form — its brilliance helped to disguise the solid base when the glass was filled.
The majority of surviving deceptive glasses date from the mid-18th century, when twist-stem glass production was at its height. Examples with air twist or opaque twist stems are the most commonly encountered and the most sought after by collectors.
Related Forms
Toastmaster's Glasses
Closely related to the deceptive glass is the toastmaster's glass — a glass used by the individual responsible for proposing and managing toasts at a formal dinner or gathering. The toastmaster was required to drink at every toast, which, over the course of a long dinner with many toasts, could amount to a considerable quantity of wine. The toastmaster's glass, like the deceptive glass, has a solid or near-solid bowl base, allowing the toastmaster to fulfil his ceremonial role without incapacitating himself before the evening was over. The distinction between a deceptive glass and a toastmaster's glass is largely one of attribution — the physical form is essentially identical.
Sham Dram Glasses
The sham dram is a related form, typically smaller and used for spirits rather than wine. The same principle applies: a solid base within the bowl reduces the actual capacity to a fraction of the apparent volume. Sham drams are found in both glass and ceramic forms.
Collecting Deceptive Glasses
Deceptive glasses occupy an appealing niche in the antique glass market — they are genuinely functional objects with a clear and entertaining purpose, they display well alongside standard drinking glasses of the period, and they invariably provoke curiosity and conversation.
Points to consider when buying:
- Condition of the bowl rim — as with all antique glasses, chips to the rim significantly affect value. Examine carefully under good light.
- Clarity of the glass — check for crizzling (internal glass deterioration), particularly on earlier examples.
- The effectiveness of the deception — the best examples are those where the solid base is genuinely difficult to detect without close examination. A poorly executed example where the base is immediately obvious is less desirable.
- Stem quality — as with all twist-stem glasses, the quality and complexity of the twist is a significant factor in value. A deceptive glass with a fine double-series air twist stem is considerably more desirable than one with a plain stem.
For collectors building a broader collection of 18th-century English glass, a deceptive glass provides a delightful counterpoint to the more straightforward drinking glasses of the period — a reminder that the 18th century had a well-developed sense of humour, and that not everything on the Georgian table was quite what it appeared.
The Wonder Room occasionally offers antique drinking glasses of the 18th century, including deceptive and illusion glasses. Browse our current collection or explore further guides in Collector's Insights.