Loading
Object Overview
The Pilot Wheel Barometer is a combined tabletop and wall-mounted barometer housed in a case styled as a ship’s wheel. It was manufactured circa 1960 by the renowned German company Lufft as an export model intended for the United States market, where it was marketed under its own model name and advertised as an instrument “Styled for the Sportsman.”
The model appears in the 1961 American issued by of New York, the official exclusive representative and importer of products in the United States. Founded in 1869, the New York import and trading firm was responsible for the importation, distribution, and servicing of German meteorological and scientific instruments for many years, effectively acting as American distributor.
n/a
aneroid capsule tensioned on a C-spring
brass, chrome, enamel, glass, nickel silver, steel, wood
In the catalogue, the manufacturer emphasised the instrument’s distinctly nautical character, its combination of decorative appeal and practical utility, and its suitability for either tabletop or wall-mounted display.
The case is formed as a traditional eight-spoked ship’s wheel, immediately evoking associations with navigation and maritime tradition. Its body is made from genuine solid American walnut, described in the original catalogue as solid walnut, and is carefully polished to a deep, silky lustre.
The wooden surface is ornamented with several concentric moulded grooves, which reinforce the circular composition of the case and visually emphasise its substantial construction. Eight symmetrically arranged wheel handles are made of brass with a highly polished mirror-chromium finish and terminate in characteristic bullet-shaped grips.
The contrast between the warm grain of natural walnut and the cool brilliance of polished chrome gives the case a strongly decorative character typical of American interior design of the late 1950s and early 1960s.
The centre of the case is occupied by a substantial chromium-plated bezel retaining a convex mineral-glass crystal.
At the centre of the glass is a knurled, fully chromium-plated rotating knob used to position the additional hand serving as the atmospheric-pressure trend indicator. This arrangement allowed the owner to mark a previous barometric reading and subsequently determine the direction of pressure change visually, without having to remember the numerical value.
The case was designed for two forms of display. A folding metal-wire stand is fitted to the rear, allowing the instrument to be placed at a convenient viewing angle on a desk, mantelpiece, shelf, or bookcase.
The upper part of the case is also equipped with a robust metal suspension loop, enabling the Pilot Wheel Barometer to be hung on a wall as a decorative nautical instrument.
Of particular interest is the original dial, made from uranium-bearing opaque glass enamel applied over steel. It should be distinguished both from uranium glass in the conventional collecting sense—that is, a three-dimensional glass object—and from custard glass.
The dial consists of a steel plate covered with a thin layer of opaque glass fused to the metal during firing. It is therefore a classic example of vitreous enamel, also known as porcelain enamel, applied over steel. Finely ground glass frit was deposited on the metal and fused to the substrate during high-temperature firing, producing a continuous amorphous silicate coating.
Its whiteness and opacity are created by an opacifier: a light-scattering phase incorporated into the glass. In mid-twentieth-century enamels this was most commonly titanium dioxide, which produced an especially bright white surface.
Uranium is present only in a very small quantity. This is apparent even without scientific instruments: in ordinary daylight the dial appears white rather than cream or yellow, indicating that the uranium concentration is too low to impart a visible colour. It was introduced in the form of uranium compounds, such as sodium uranate or uranium oxides. The fluorescent component is the uranyl ion, UO₂²⁺, dispersed throughout the silicate network.
In this white dial, uranium does not perform a colouring function. The whiteness is created by the opacifying agent, while the uranium is either an impurity inherited from the raw materials and frit or a minor deliberate additive. Its presence is revealed primarily by fluorescence. Under long-wave ultraviolet light at 365 nm, the enamel emits an intense green glow. Excitation of the uranyl ion follows its absorption spectrum, which is strongest in the near-ultraviolet region, with a maximum around 330 nm, and diminishes sharply toward 400 nm.
The uranium used in such manufactured products was chemically refined. Consequently, only the initial members of the uranium decay series remain in significant association with it, principally thorium-234 and traces of metastable protactinium-234, while radium, lead, and bismuth were removed during processing. This has a historical explanation. Uranium compounds were originally produced as by-products of radium extraction, during which the naturally occurring daughter products present in the ore were separated. Colouring uranium was sold as an ordinary industrial chemical, including uranium yellow, or sodium diuranate, together with various uranium oxides, and could be purchased by glassworks and enamelling factories from commercial chemical suppliers.
Natural uranium was historically used before the Second World War, notably in well-known uranium-glass tableware. When production resumed during the 1950s, depleted uranium—a by-product of uranium enrichment—was increasingly employed.
Uranium-glass tableware is considerably older than the Pilot Wheel Barometer. Its origins can be traced to Bohemia in approximately the 1830s, particularly to the Annagrün and Annagelb glasses associated with the Riedel family. Its greatest periods of popularity occurred during the Victorian era and again among the decorative and Depression glass wares of the 1920s to 1940s.
Production was interrupted during the period of the Manhattan Project but resumed during the 1950s, generally using depleted uranium. In the United States this followed renewed permission from the Atomic Energy Commission for controlled industrial use of uranium compounds. Fenton, for example, returned to uranium-bearing glass production in the late 1950s.
Uranium glass has continued to be manufactured into the modern period by firms including Fenton, Mosser, and various Czech glassworks. Fenton produced both custard glass and more transparent forms of uranium glass, including colours marketed as Vaseline and Lime Sherbet.
The celebrated pre-war vintage wares generally contain natural uranium, but uranium glass as a material category is not confined to a single period. Post-war and modern examples more commonly contain depleted uranium.
The radioactivity of the dial material is low. When intact, the enamel is chemically stable and safe to handle under ordinary collecting and display conditions.
The trace uranium content produces a modest but consistent elevation above natural background radiation that can be detected with a handheld instrument through its alpha and beta channels when the protective glass is removed. The measured dose rate directly at the dial surface is approximately 0.70 µSv/h, compared with a local background level of approximately 0.06 µSv/h, or around twelve times background. This measurement supports the identification of uranium within the enamel.
The uranium-bearing enamel should not be confused with custard glass. The resemblance is limited to the mechanism responsible for green fluorescence; in every other respect the materials belong to different categories.
The confusion is nevertheless understandable, particularly because genuine custard-glass dials do exist. Such dials were more widely used in clockmaking than in barometer manufacture, especially in mantel and table clocks dating from the late nineteenth and early twentieth centuries. Their fluorescent faceplates are now valued by collectors.
Custard glass is a type of decorative glass that became fashionable during the second half of the nineteenth century, reaching the height of its popularity between approximately 1890 and 1915. It is an opaque or semi-translucent pressed glass of warm cream-yellow or ivory colour. Its English name derives from its resemblance to custard, while it was initially marketed under names such as ivory glass.
In England, the firm Sowerby produced it under the trade name Queen’s Ivory Ware, while the general formulation had developed in Bohemia during the 1870s. Its warm colour and fluorescence were produced by uranium compounds, particularly sodium diuranate, sometimes combined with sulphur, in quantities sufficient to produce visible yellow coloration.
Under ultraviolet light, custard glass fluoresces green, although the glow often appears softer and more moss-like than that of transparent uranium glass because the opaque body absorbs part of its own emitted light.
A custard-glass dial is readily recognisable as a self-supporting disc of dense cream-yellow glass rather than a coating applied to a metal substrate. Its yellow colour is clearly visible in ordinary daylight.
In addition to clock dials, was used principally for tableware and decorative objects, including tumblers, butter dishes, sugar bowls, creamers, bowls, vases, and souvenir pieces. Manufacturers included the American companies , , , , , , , and ; the English firms and ; and the Bohemian manufacturer . During the Great Depression, pieces of were sometimes included in commercial product packaging as promotional gifts, a well-known example being their distribution with products.
The distinction between custard glass and the dial of the Pilot Wheel Barometer may therefore be reduced to three principal points.
First, the form and material category differ: custard glass is a solid, three-dimensional glass object, whereas the barometer dial consists of a thin vitreous-enamel coating fused to steel.
Second, the colour differs: custard glass is cream-yellow, while the barometer dial is white.
Third, the role of uranium differs: in custard glass, uranium is present in sufficient quantity to contribute to the visible colour, whereas in the enamel dial it occurs only in trace amounts and has no perceptible effect on the daylight appearance.
The two materials share only the presence of the uranyl ion and its characteristic green fluorescence. In other words, the Pilot Wheel Barometer has a white enamel dial containing traces of uranium, not a dial made from uranium-coloured glass.
The barometer has an annular dial with an open centre, a configuration known as an open dial. Through the central aperture, the aneroid mechanism remains visible, including the polished chain transmission and the corrugated aneroid capsule.
The barometric scale extends around the entire circumference of the ring. It is calibrated in English, or “London,” inches of mercury over the range from 28 to 31 inHg. Each inch is divided into numbered tenths and further subdivided by fine graduations into fiftieths of an inch, giving an interval of 0.02 inHg.
The range of 28–31 inches of mercury was standard for traditional English-language domestic barometers and was particularly appropriate for an export instrument intended for the American market.
The scale incorporates traditional written weather indications positioned along the arc above the corresponding pressure zones:
Stormy — Rain — Change — Fair — Very Dry
These terms are rendered in a decorative Gothic or blackletter typeface, also commonly described as Old English. Their most distinctive feature is the use of rubrication: the initial capital letter of each word is printed in red, while the remaining letters are black. Small ornamental flourishes and vignettes separate the individual terms.
This typographic treatment gives the dial an intentionally antiquarian and maritime appearance. The word Germany is printed at the lower edge of the scale, identifying the country of origin and reflecting the instrument’s status as an export model.
The instrument is operated by a conventional aneroid mechanism. Its sensitive element is a multiply corrugated aneroid capsule from which most of the air has been evacuated.
To prevent the thin metal diaphragms from collapsing under atmospheric pressure, the capsule is held under constant tension by an elastic C-shaped steel spring that counteracts the external load.
Changes in atmospheric pressure cause minute movements in the walls of the capsule. These movements are transmitted to a system of amplifying levers, which increases their effective travel. Motion is then conveyed to the pointer arbor by means of a miniature fusee chain, one of the most elegant and precise forms of transmission used in high-quality aneroid barometers.
The Pilot Wheel Barometer is a characteristic example of Lufft’s export production, combining German precision instrument-making with the aesthetics of the American post-war interior.
Its unusual ship’s-wheel form, solid walnut case, extensive chromium-plated fittings, uranium-bearing fluorescent vitreous-enamel dial, and refined chain-driven aneroid mechanism make it both a fully functional meteorological instrument and a striking decorative object.
The discreet presence of uranium within the white enamel—visually imperceptible in daylight yet revealed by its intense green ultraviolet fluorescence—adds a particularly unusual technological and material dimension to the instrument. Together, these features reflect the popularity of nautical themes in decorative design at the transition from the 1950s to the 1960s.