A mug is a type of cup,[1] a drinking vessel usually intended for hot drinks such as: coffee, hot chocolate, or tea. Mugs usually have handles and hold a larger amount of fluid than other types of cups such as teacups or coffee cups. Typically, a mug holds approximately 250–350 ml (8–12 US fl oz) of liquid.[2] A mug-shaped vessel much larger than this tends to be called a tankard.
Mugs typically have a straight-line profile, either perpendicular or flaring. But this is not defining for the form, and a curving profile is possible. But a single vertical handle is essential (otherwise the vessel is a beaker), as is the lack of a matching saucer.[3] A mug is a less formal style of drink container and is not usually used in formal place settings, where a teacup or coffee cup is preferred. Shaving mugs are used to assist in wet shaving.
Ancient mugs were usually carved in wood or made of pottery, while most modern ones are made of pottery materials such as bone china, earthenware, porcelain, or stoneware. Large mugs, typically made of metal or pottery and used for drinking beer, are likely to be called tankards. Some mugs are made from strengthened glass, such as Pyrex. Other materials, including enameled metal, plastic, or steel are preferred, when reduced weight or resistance to breakage is at a premium, such as for camping. A travel mug is insulated and has a cover with a small sipping opening to prevent spills. Techniques such as silk screen printing or decals are used to apply decorations such as logos or images and fan art, which are fired onto the mug to ensure permanence.
Though today mugs are associated with hot drinks, milk and soft drinks, many early mugs appear to have been mostly used for beer or other alcoholic drinks, and were often larger than modern mugs. Wooden mugs were produced probably from the earliest days of woodworking, but most of them have not survived or stayed intact.[4][5]
The first pottery was shaped by hand and was later facilitated by the invention of the potter’s wheel (date unknown, between 6,500 and 3000 BCE). It was relatively easy to add a handle to a cup in the process thus producing a mug. For example, a rather advanced, decorated clay mug from 4000 to 5000 BCE was found in Greece.[6]
Ancestral Pueblo (Anasazi) mugs from SW Colorado, made between 1000 and 1280 CE. The meaning of the carving in the handles is as yet unknown, but it is probably not functional.
The biggest disadvantage of those clay mugs was thick walls unfit for the mouth. The walls were thinned with development of metalworking techniques. Metal mugs were produced from bronze,[7]silver, gold,[8] and even lead,[9] starting from roughly 2000 BCE, but were hard to use with hot drinks.
The invention of porcelain around 600 CE in China brought a new era of thin-walled mugs suitable both for cold and hot liquids, which are enjoyed today.[4][5]
A shaving scuttle and shaving mug were developed around the 19th century; the first patent for a shaving mug is dated 1867.[10] As hot water was not common in many households, one way to provide hot lather was to use a scuttle or mug. A traditional scuttle resembles a teapot with a wide spout where hot water is poured in; this is where it differs from a shaving mug, which has no spout. Both shaving scuttles and mugs usually have a handle, but some have none. Shaving mugs often look like a standard mug, however, some also have a built in brush rest, so the brush does not sit in lather. Modern versions of the scuttle are in limited production, usually by independent potters working in small volumes.[11]
At the top of the scuttle or mug is a soap holder. Traditionally, it was used with a hard block of shaving soap (rather than soft soap or cream) and therefore had drain holes at the bottom. Later scuttles and mugs do not include the holes, and thus can be used with creams and soft soaps. Some scuttles and mugs have concentric circles on the bottom, which retain some water thus helping to build lather.[11]
In use, the shaving brush is dunked into the wide spout, allowing it to soak into the water and heat up. The soap is placed in the soap holder. When needed, one can take the brush and brush it against the soap, bringing up a layer of lather; excess water is drained back. This allows conservation of water and soap, whilst retaining enough heat to ensure a long shave.
Tiki mugs, drinking vessels usually made of ceramics, originated in mid-20th century tropical themed restaurants and tiki bars. The term “Tiki mugs” is a generic, blanket term for sculptural drink ware that depict imagery from Melanesia, Micronesia, or Polynesia, and more recently anything tropical or related to surfing. Often sold as souvenirs, tiki mugs are highly collectable. Modern manufacturers include Muntiki and Tiki Farm. Individual artists, such as Van Tiki, also produced limited one-of-a-kind hand sculpted mugs.[12]
Travel mugs (introduced in the 1980s[citation needed]) generally employ thermal insulation properties for transporting hot or cold liquids. Similar to a vacuum flask, a travel mug is usually well-insulated and completely enclosed to prevent spillage[13] or leaking, but will generally have an opening in the cover through which the contents can be consumed during transportation without spillage. As the primary mechanism by which hot (not warm) beverages lose heat is evaporation, a lid serves a vital role in keeping the drink hot; even a thin plastic one which conducts heat quite quickly.
Mugs with inner and outer walls, but not vacuum treated, are generally called double wall mugs. Usually stainless steel will be used for the inner wall while outer wall can be stainless steel, plastic, or even embedded with other materials.
Mugs designed for use when driving are called auto mugs or commuter mugs. Travel mugs have a spill-proof lid with a sipping opening[14] and in many cases, a narrower base, so that they will fit into the cup-holders that are built into many vehicles.[citation needed] Additional criteria for evaluating auto mugs include: they must be easy to open single-handedly (to prevent distractions while driving), include a fill line (to prevent over-filling, which contributes to leaking), preferably have no handles (no-handled mugs are easier to grab while driving), should not obstruct a driver’s view of the road when he or she is drinking, and – with regard to cup-holders be able to fit, stably, into a wide range of mug holders.[15][14][16]
The whistle mug or hubblebubble is an amusement mug. It has a hollow handle which can be blown through the mug like a whistle. With an empty mug, only one note is emitted, whereas a filled mug produces melodious trills and warblings.[17]
A Pythagorean cupFuddling cups. The cups have hollow interconnections that allow the contents to be drunk without spilling.
A puzzle mug is a mug which has some trick preventing normal operation. One example is a mug with multiple holes in the rim, making it impossible to drink from it in the normal way. Although it is tempting to grasp the body of the mug covering the visible holes and drink the liquid in the usual manner, this would pour the liquid through hidden perforations near the mug’s top. The solution is to cover the holes in the rim with hands, but to drink not through the top, but through a “secret” hole in the hollow handle.[17]
A puzzle mug called fuddling cups consists of three mugs connected through their walls and handles. The inner holes in the mugs walls are designed in such a way that the mugs must be emptied in a unique sequence, or they will drain.[17]
The Pythagorean cup (see picture) contains a small siphon hidden in a rod placed in the mug center. The cup holds liquid if filled below the height of the rod, but once filled above that level, it drains all liquid through the siphon to a hole in its base.
Heat changing mugs
[edit]Duration: 35 seconds.0:35Video of hot water being poured into a “magic mug” and the subsequent colour change
Heat changing, heat sensitive, or magic mugs make use of thermochromism to change appearance when a hot beverage is poured into them.
Much of the mug design aims at thermal insulation: the thick walls of a mug, as compared to the thinner walls of teacups, insulate the beverage to prevent it from cooling or warming quickly. The mug bottom is often not flat, but either concave or has an extra rim, to reduce the thermal contact with the surface on which a mug is placed. These features often leave a characteristic circular stain on the surface. Finally, the handle of a mug keeps the hand away from the hot sides of a mug. The small cross section of the handle reduces heat flow between the liquid and the hand. For the same reason of thermal insulation, mugs are usually made of materials with low thermal conductivity, such as earthenware, bone china, porcelain, or glass.[18][19]
As a ubiquitous desktop item, the mug is often used as an object of art or advertisement; some mugs are rather decorations than drinking vessels. Carving had been traditionally applied to mugs in the ancient times. Deforming a mug into an unusual shape is sometimes used. However, the most popular decoration technique nowadays is printing on mugs, which is usually performed as follows: Ceramic powder is mixed with dyes of chosen color and a plasticizer. Then it is printed on a gelatin-coated paper using a traditional screen-printing technique, which applies the mixture through a fine woven mesh, which is stretched on a frame and has a mask of desired shape. This technique produces a thin homogeneous coating; however, if smoothness is not required, the ceramic mixture is painted directly with a brush. Another, more complex alternative is to coat the paper with a photographic emulsion, photoprint the image and then cure the emulsion with ultraviolet light.[20]
After drying, the printed paper, called a litho, can be stored indefinitely. When a litho is applied to the mug, it is first softened in warm water. This detaches the gelatin cover, with the printed image, from the paper; this cover is then transferred to the mug. The mug is then fired around 700–750 °C (1,290–1,380 °F; 970–1,020 K), which softens the top surface of the glaze, thereby embedding the image into it.[20]
A popular way to store mugs is on a ‘mug tree’, a wooden or metal pole mounted on a round base and fitted with pegs to hang mugs by their handles.[21] There are also racks designed for hanging mugs so that they are ready to hand. Those are especially useful on ships in high waves. Mugs can often be a collectible item, making storage and display tools/strategies something important to think about for collectors.
A continuous deformation between a coffee mug and a donut illustrating that they are homeomorphic (topologically equivalent)
The mug serves as one of the most popular examples of homeomorphism in topology. Two objects are homeomorphic if one can be deformed into the other without cutting or gluing. Thus in topology, a mug is equivalent (homeomorphic) to a doughnut (torus) as it can be reshaped into a doughnut by a continuous deformation, without cutting, breaking, punching holes or gluing.[22] Another topological example is a mug with two handles, which is equivalent to a double torus – an object resembling number 8.[23] A mug without a handle, i.e., a bowl or a beaker, is topologically equivalent to a saucer, which is quite evident when a raw clay bowl is flattened on a potter’s wheel.[24]
Many languages − including French, Italian, Polish, Russian, German − use two separate words for mugs and traditional cups. Anna Wierzbicka suggested that this situation is due to a slightly different functionality: the traditional cups are designed for drinking while sitting down at the table, while the mug is supposed to be used anywhere. This, in her opinion, explains all the specific features:[25]
The saucer of the cup helps to protect the table surface, but is an inconvenience away from the table.
The tapered shape of the cup accommodates the saucer, the cylindrical design of the mug is due to the absence of the saucer.
Larger handle of a mug allows carrying the mug around when putting it down is not an option.
Thicker walls of a mug allow cupping it with a second hand for convenience and reduce the chance of the mug being broken during long periods of handling.
Sitting at the table implies a more formal occasion, so cups are made to be more elegant, and sold in sets (like a tea set or a coffee service). Mugs are informal and usually sold individually.
A mug holds more liquid than a cup. Since limiting the area of the exposed surface of the liquid helps keeping the temperature of hot drinks, this increase in volume is achieved through mug being taller, while tapered cups are lower for stability.
Glasses, also known as eyeglasses, spectacles, or colloquially as specs, are visioneyewear with clear or tinted lenses mounted in a frame that holds them in front of a person’s eyes, typically utilizing a bridge over the nose and hinged arms, known as temples or temple pieces, that rest over the ears for support.
Glasses are typically used for vision correction, such as with reading glasses and glasses used for nearsightedness; however, without the specialized lenses, they are sometimes used for cosmetic purposes.
Safety glasses provide eye protection against flying debris for construction workers or lab technicians; these glasses may have protection on the sides of the eyes as well as in the lenses. Some types of safety glasses are used to protect against visible and near-visible light or radiation. Glasses are worn for eye protection in some sports, such as squash.
Glasses wearers may use a strap to prevent the glasses from falling off. Wearers of glasses that are used only part of the time may have the glasses attached to a cord that goes around their neck to prevent the loss and breaking of the glasses.
Sunglasses allow for better vision in bright daylight and are used to protect one’s eyes against damage from excessive levels of ultraviolet light. Typical sunglasses lenses are tinted for protection against bright light or polarized to remove glare; photochromic glasses are clear or lightly tinted in dark or indoor conditions, but turn into sunglasses when they come into contact with ultraviolet light. Most over-the-counter sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be made. People with conditions that have photophobia as a primary symptom (like certain migraine disorders) often wear sunglasses or precision tinted glasses, even indoors and at night.
Specialized glasses may be used for viewing specific visual information, for example, 3D glasses for 3D films (stereoscopy). There are also blue light glasses that people wear to protect their eyes from harmful bluelight in computer screens, phones, and other technological devices. Sometimes glasses are worn purely for fashion or aesthetic purposes. Even with glasses used for vision correction, a wide range of fashions are available, using plastic, metal, wire, and other materials for frames. Most glasses lens are made of plastic, polyethylene, and glass.
Glasses can be marked or found by their primary function, but also appear in combinations such as prescription sunglasses or safety glasses with enhanced magnification.
A skyline seen through a corrective lens, showing the effect of refractionMicrofiber cloth designed for cleaning corrective lenses without scratching sensitive glass
Corrective lenses are used to correct refractive errors by bending the light entering the eye in order to alleviate the effects of conditions such as nearsightedness (myopia), farsightedness (hypermetropia) or astigmatism. The ability of one’s eyes to accommodate their focus to near and distant focus alters over time. A common condition in people over forty years old is presbyopia, which is caused by the eye’s crystalline lens losing elasticity, progressively reducing the ability of the lens to accommodate (i.e. to focus on objects close to the eye). Few people have a pair of eyes that show exactly equal refractive characteristics; one eye may need a “stronger” (i.e. more refracting) lens than the other.
Corrective lenses bring the image back into focus on the retina. They are made to conform to the prescription of an ophthalmologist or optometrist. A lensmeter can be used to verify the specifications of an existing pair of glasses. Corrective eyeglasses can significantly improve the life quality of the wearer. Not only do they enhance the wearer’s visual experience, but can also reduce problems that result from eye strain, such as headaches or squinting.
The most common type of corrective lens is “single vision”, which has a uniform refractive index. For people with presbyopia and hyperopia, bifocal and trifocal glasses provide two or three different refractive indices, respectively, and progressive lenses have a continuous gradient.[1] Lenses can also be manufactured with high refractive indices, which allow them to be more lightweight and thinner than their counterparts with “low” refractive indices.
Reading glasses provide a separate set of glasses for focusing on close by objects. Reading glasses are available without prescription from drugstores, and offer a cheap, practical solution, though these have a pair of simple lenses of equal power, and so will not correct refraction problems like astigmatism or refractive or prismatic variations between the left and right eye. For the total correction of the individual’s sight, glasses complying to a recent ophthalmic prescription are required.
People who need glasses to see often have corrective lens restrictions on their driver’s licenses that require them to wear their glasses every time they drive or risk fines or jail time.
Some militaries issue prescription glasses to servicemen and women. These are typically GI glasses. Many state prisons in the United States issue glasses to inmates, often in the form of clear plastic aviators.
Adjustable-focus eyeglasses might be used to replace bifocals or trifocals, or might be used to produce cheaper single-vision glasses (since they do not have to be custom-manufactured for every person).
Pinhole glasses are a type of corrective glasses that do not use a lens. Pinhole glasses do not actually refract the light or change focal length. Instead, they create a diffraction limited system, which has an increased depth of field, similar to using a small aperture in photography. This form of correction has many limitations that prevent it from gaining popularity in everyday use. Pinhole glasses can be made in a DIY fashion by making small holes in a piece of card which is then held in front of the eyes with a strap or cardboard arms.
Glasses may also house other corrective or assistive devices. After the development of the transistor in the 1940s, combined eyeglass-hearing aids became popular. With thick-rimmed glasses the fashion at the time, a hearing aid could be concealed in the temple part of the frame. These fell out of fashion after the 1970s, but there are still occasions when combined eyeglass-hearing aids may be useful.[3]
Safety glasses are worn to protect the eyes in various situations. They are made with break-proof plastic lenses to protect the eye from flying debris or other matter.[4] Construction workers, factory workers, machinists and lab technicians are often required to wear safety glasses to shield the eyes from flying debris or hazardous splatters such as blood or chemicals.[5] As of 2017, dentists and surgeons in Canada and other countries are required to wear safety glasses to protect against infection from patients’ blood or other body fluids. There are also safety glasses for welding, which are styled like wraparound sunglasses, but with much darker lenses, for use in welding where a full-sized welding helmet is inconvenient or uncomfortable. These are often called “flash goggles” because they provide protection from welding flash.[6]Nylon frames are usually used for protective eyewear for sports because of their lightweight and flexible properties. Unlike most regular glasses, safety glasses often include protection beside the eyes as well as in front of the eyes.
Sunglasses provide more comfort and protection against bright light and often against ultraviolet (UV) light. To properly protect the eyes from the dangers of UV light, sunglasses should have UV-400 blocker to provide good coverage against the entire light spectrum that poses a danger.[7]
Light polarization is an added feature that can be applied to sunglass lenses. Polarization filters are positioned to remove horizontally polarized rays of light, which eliminates glare from horizontal surfaces (allowing wearers to see into water when reflected light would otherwise overwhelm the scene). Polarized sunglasses may present some difficulties for pilots since reflections from water and other structures often used to gauge altitude may be removed. Liquid-crystal displays emit polarized light, making them sometimes difficult to view with polarized sunglasses. Sunglasses may be worn for aesthetic purposes, or simply to hide the eyes. Examples of sunglasses that were popular for these reasons include tea shades and mirrorshades. Many blind people wear nearly opaque glasses to hide their eyes for cosmetic reasons. Many people with light sensitivity conditions wear sunglasses or other tinted glasses to make the light more tolerable.
Sunglasses may also have corrective lenses, which requires a prescription. Clip-on sunglasses or sunglass clips can be attached to another pair of glasses. Some wrap-around sunglasses are large enough to be worn over another pair of glasses. Otherwise, many people opt to wear contact lenses to correct their vision so that standard sunglasses can be used.
Double-frame eyewear with one set of lenses on the moving frame and another pair of lenses on a fixed frame (optional).
The double frame uplifting glasses have one moving frame with one pair of lenses and the basic fixed frame with another pair of lenses (optional), that are connected by four-bar linkage. For example, sun lenses could be easily lifted up and down while mixed with myopia lenses that always stay on. Presbyopia lenses could be also combined and easily removed from the field of view if needed without taking off glasses. These glasses are often used for drivers going through tunnels, with the upper frame serving as sunglasses and the second frame as transparent lenses.
The illusion of three dimensions on a two-dimensional surface can be created by providing each eye with different visual information. 3D glasses create the illusion of three dimensions by filtering a signal containing information for both eyes. The signal, often light reflected off a movie screen or emitted from an electronic display, is filtered so that each eye receives a slightly different image. The filters only work for the type of signal they were designed for.
Anaglyph 3D glasses have a different colored filter for each eye, typically red and blue or red and green. A polarized 3D system on the other hand uses polarized filters. Polarized 3D glasses allow for color 3D, while the red-blue lenses produce an image with distorted coloration. An active shutter 3D system uses electronic shutters. Head-mounted displays can filter the signal electronically and then transmit light directly into the viewer’s eyes.
Anaglyph and polarized glasses are distributed to audiences at 3D movies. Polarized and active shutter glasses are used with many home theaters. Head-mounted displays are used by a single person, but the input signal can be shared between multiple units.
Glasses can also provide magnification that is useful for people with vision impairments or specific occupational demands. An example would be bioptics or bioptic telescopes which have small telescopes mounted on, in, or behind their regular lenses. Newer designs use smaller lightweight telescopes, which can be embedded into the corrective glass and improve aesthetic appearance (mini telescopic spectacles). They may take the form of self-contained glasses that resemble goggles or binoculars, or may be attached to existing glasses.
Recumbent or prism glasses are glasses that use a prism with a 90° refraction to allow the wearer to read or view a screen while lying on their back. Developed by Liverpudlian ophthalmologist Andrew McKie Reid in the 1930s to assist people bedbound by chronic illness or spinal injury, recumbent glasses have more recently been marketed not simply as an assistive device but also as ‘lazy glasses’.[9] They do not assist with vision, although they can be worn over regular corrective glasses.
Yellow-tinted glasses are a type of glasses with a minor yellow tint. They perform a slight color correction, on top of reducing eyestrain from lack of blinking. They may also be considered minor corrective non-prescription glasses.[10] Depending on the company, these computer or gaming glasses can also filter out high energy blue and ultra-violet light from LCD screens, fluorescent lighting, and other sources of light. This allows for reduced eye-strain.[11] These glasses can be ordered as standard or prescription lenses that fit into standard optical frames.[12]
By the end of the 2010s, eyeglasses that filter out blue light from computers, smartphones and tablets are becoming increasingly popular in response to concerns about problems caused by blue light overexposure.[13][14] The problems claimed range from dry eyes to eye strain, sleep cycle disruption, up to macular degeneration which can cause partial blindness.[13] They may also block out ultraviolet (UV) radiation. However, there is no measurable UV light from computer monitors.[13][15][contradictory] The problem of computer vision syndrome (CVS) can result from focusing the eyes on a screen for long, continuous periods. Many times the glasses do not appear to have much of a tint, or, if any, a slight yellow tint, but they may be more heavily tinted.
Long hours of computer use (not blue light) may cause eye strain.[13][16][14][17] Many eye symptoms caused by computer use will lessen after the usage of the computer is stopped.[13] Decreasing evening screen time and setting devices to night mode will improve sleep.[16][18] Several studies have shown that blue light from computers does not lead to eye diseases, including macular degeneration.[16][19][20] The total amount of light entering the eyes can be adjusted without glasses using the screen brightness settings. Similarly, the blue light can often specifically be adjusted using the “night mode” of different operating systems, which can usually be activated outside of nighttime hours.
The American Academy of Ophthalmology (AAO) does not recommend special eyewear for computer use,[13][14] although it recommends using prescription glasses measured specifically for computer screen distance (depending on individuals, but possibly 20–26 inches from the face), which are not the same as “blue-light blocking” glasses.[21] The position of the College of Optometrists (UK) is that “the best scientific evidence currently available does not support the use of blue-blocking spectacle lenses in the general population to improve visual performance, alleviate the symptoms of eye fatigue or visual discomfort, improve sleep quality or conserve macula health.”[22]
The ophthalmic frame is the part of a pair of glasses that is designed to hold the lenses in the proper position. Ophthalmic frames come in a variety of styles, sizes, materials, shapes, and colors.[23]
pair of eye wires or rims surrounding and holding the lenses in place
bridge which connects the two eye wires
chassis, the combination of the eye wires and the bridge
top bar or brow bar, a bar just above the bridge providing structural support and/or style enhancement (country/Grandpa style). The addition of a top bar makes a pair of glasses aviator eyeglasses
pair of brows or caps, plastic or metal caps which fit over the top of the eye wires for style enhancement and to provide additional support for the lenses. The addition of brows makes a pair of glasses browline glasses
pair of nose pads that allows a comfortable resting of the eye wires on the nose
pair of pad arms connect the nose pads to the eye wires
pair of temples (earpieces) on either side of the skull
pair of temple tips at the ends of the temples
pair of end pieces connect the eye wires via the hinges to the temples
pair of frame-front end pieces
pair of hinges connect the end pieces to the temples, allowing a swivel movement. Spring-loaded flex hinges are a variant that is equipped with a small spring that affords the temples a greater range of movement and does not limit them to the traditional, 90-degree angle.
Skull temples: bend down behind the ears, follow the contour of the skull and rest evenly against the skull
Library temples: generally straight and do not bend down behind the ears. Hold the glasses primarily through light pressure against the side of the skull
Convertible temples: used either as library or skull temples depending on the bent
Riding bow temples: curve around the ear and extend down to the level of the ear lobe. Used mostly on athletic, children’s, and industrial safety frames
Comfort cable temples: similar to the riding bow, but made from a springy cable of coiled metal, sometimes inside a plastic or silicone sleeve. The tightness of the curl can be adjusted along its whole length, allowing the back to fit the wearer’s ear curve perfectly. Used for physically active wearers, children, and people with high prescriptions (heavy lenses).[24][25] See the image of 1920s frames above.
Optyl, a type of hypoallergenic material made especially for eyeglass frames. It features a type of elasticity that returns the material to its original shape.
Corrective lenses can be produced in many different shapes from a circular lens called a lens blank. Lens blanks are cut to fit the shape of the frame that will hold them. Frame styles vary and fashion trends change over time, resulting in a multitude of lens shapes. For lower power lenses, there are few restrictions, allowing for many trendy and fashionable shapes. Higher power lenses can distort peripheral vision and may become thick and heavy if a large lens shape is used. However, if the lens is too small, it can drastically reduce the field of view.
Bifocal, trifocal, and progressive lenses generally require a taller lens shape to leave room for the different segments while preserving an adequate field of view through each segment. Frames with rounded edges are the most efficient for correcting myopic prescriptions, with perfectly round frames being the most efficient. Before the advent of eyeglasses as a fashion item, when frames were constructed with only functionality in mind, virtually all eyeglasses were either round, oval, panto, rectangular, octagonal, or square. It was not until glasses began to be seen as an accessory that different shapes were introduced to be more aesthetically pleasing than functional.
Scattered evidence exists for use of visual aid devices in Greek and Roman times, most prominently the use of an emerald by Emperor Nero as mentioned by Pliny the Elder.[27]
The use of a convex lens to form an enlarged/magnified image was most likely described in Ptolemy‘s Optics (which survives only in a poor Arabic translation). Ptolemy’s description of lenses was commented upon and improved by Ibn Sahl (10th century) and most notably by Alhazen (Book of Optics, c. 1021). Latin translations of Ptolemy’s Optics and of Alhazen became available in Europe in the 12th century, coinciding with the development of “reading stones“.
There are claims that single lens magnifying glasses were being used in China during the Northern Song dynasty (960–1127).[28][29]
Robert Grosseteste‘s treatise De iride (On the Rainbow), written between 1220 and 1235, mentions using optics to “read the smallest letters at incredible distances”.[30] A few years later in 1262, Roger Bacon is also known to have written on the magnifying properties of lenses.[31][32] The development of the first eyeglasses took place in northern Italy in the second half of the 13th century.[33]
Independently of the development of optical lenses, some cultures developed “sunglasses” for eye protection, without any corrective properties.[34] For example, flat panes of smoky quartz were used in 12th-century China, and the Inuit have used snow goggles for eye protection.[a]
The earliest recorded comment on the use of lenses for optical purposes was made in 1268 by Roger Bacon.[36]
The first eyeglasses were estimated to have been made in Central Italy, most likely in Pisa or Florence, by about 1290: In a sermon delivered on 23 February 1306, the Dominican friar Giordano da Pisa (c. 1255–1311) wrote “It is not yet twenty years since there was found the art of making eyeglasses, which make for good vision … And it is so short a time that this new art, never before extant, was discovered. … I saw the one who first discovered and practiced it, and I talked to him.”[37]
Giordano’s colleague Friar Alessandro della Spina of Pisa (d. 1313) was soon making eyeglasses. The Ancient Chronicle of the Dominican Monastery of St. Catherine in Pisa records: “Eyeglasses, having first been made by someone else, who was unwilling to share them, he [Spina] made them and shared them with everyone with a cheerful and willing heart.”[38]Venice quickly became an important center of manufacture, especially due to using the high-quality glass made at Murano.[39] By 1301, there were guild regulations in Venice governing the sale of eyeglasses[40] and a separate guild of Venetian spectacle makers was formed in 1320.[39] In the fourteenth century, they were very common objects: Francesco Petrarca says in one of his letters that, until he was 60, he did not need glasses,[41][42] and Franco Sacchetti mentions them often in his Trecentonovelle.
The earliest pictorial evidence for the use of eyeglasses is Tommaso da Modena‘s 1352 portrait of the cardinal Hugh de Saint-Cher reading in a scriptorium. Another early example would be a depiction of eyeglasses found north of the Alps in an altarpiece of the church of Bad Wildungen, Germany, in 1403. These early glasses had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom of aging. Although concave lenses for myopia (near-sightedness) had made their first appearance in the mid-15th century,[39] it was not until 1604 that Johannes Kepler published the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia.[b]
Early frames for glasses consisted of two magnifying glasses riveted together by the handles so that they could grip the nose. These are referred to as “rivet spectacles”. The earliest surviving examples were found under the floorboards at Kloster Wienhausen, a convent near Celle in Germany; they have been dated to circa 1400.[45]
The world’s first specialist shop for spectacles—what we might regard today as an optician—opened in Strasbourg (then Holy Roman Empire, now France) in 1466.[46]
Marco Polo is mistakenly claimed to have encountered eyeglasses during his travels in China in the 13th century. However, no such evidence appears in his accounts.[49][50] Indeed, the earliest mentions of eyeglasses in China occur in the 15th century and those Chinese sources state that eyeglasses were imported.[51]
In 1907, Professor Berthold Laufer speculated, in his history of glasses, that for glasses to be mentioned in the literature of China and Europe at approximately the same time it was probable that they were not invented independently, and after ruling out the Turks, proposed India as a location.[52][c] However, Joseph Needham speculated that the mention of glasses in the Chinese manuscript Laufer used “in part” to credit the prior invention of them in Asia did not exist in older versions of that manuscript, and the reference to them in later versions was added during the Ming dynasty.[53]
In 1971, Rishi Agarwal, in an article in the British Journal of Ophthalmology, states that Vyasatirtha was observed in possession of a pair of glasses in the 1520s, he argues that it “is, therefore, most likely that the use of lenses reached Europe via the Arabs, as did Hindu mathematics and the ophthalmological works of the ancient Hindu surgeon Sushruta“,[54] but all dates are given well after the existence of eyeglasses in Italy was established, including significant shipments of eyeglasses from Italy to the Middle East, with one shipment as large as 24,000 glasses,[55] as well as a spectacles dispensary in Strasbourg in 1466.[46]
The American scientist Benjamin Franklin, who had both myopia and presbyopia, invented bifocals. Historians have from time to time produced evidence to suggest that others may have preceded him in the invention; however, a correspondence between George Whatley and John Fenno, editor of The Gazette of the United States, suggested that Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought.[56] The first lenses for correcting astigmatism were designed by the British astronomer George Airy in 1825.[57]
Over time, the construction of frames for glasses also evolved. Early eyepieces were designed to be either held in place by hand or by exerting pressure on the nose (pince-nez). Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon passed over the wearer’s head, this in turn secured by the weight of a hat. The modern style of glasses, held by temples passing over the ears, was developed sometime before 1727, possibly by the British optician Edward Scarlett. These designs were not immediately successful, however, and various styles with attached handles such as “scissors-glasses” and lorgnettes were also fashionable from the second half of the 18th century and into the early 19th century.
In the early 20th century, Moritz von Rohr and Zeiss (with the assistance of H. Boegehold and A. Sonnefeld[58]) developed the Zeiss Punktal spherical point-focus lenses that dominated the eyeglass lens field for many years. In 2008, Joshua Silver designed eyewear with adjustable corrective glasses. They work by using a built-in syringe to pump a silicone solution into a flexible lens.[59]
Despite the popularity of contact lenses and lasercorrective eye surgery, glasses remain very common, as their technology has improved. For instance, it is now possible to purchase frames made of special memory metal alloys that return to their correct shape after being bent. Other frames have spring-loaded hinges. Either of these designs offer dramatically better ability to withstand the stresses of daily wear and the occasional accident. Modern frames are also often made from strong, lightweight materials such as titanium alloys, which were not available in earlier times.
In the 1930s, “spectacles” were described as “medical appliances”.[60] Wearing spectacles was sometimes considered socially humiliating. In the 1970s, fashionable glasses started to become available through manufacturers, and governments also recognized the demand for stylized eyewear.[60]
Graham Pullin describes how devices for disability, like glasses, have traditionally been designed to camouflage against the skin and restore ability without being visible.[60] In the past, design for disability has “been less about projecting a positive image as about trying not to project an image at all”.[60] Pullin uses the example of spectacles, traditionally categorized as a medical device for “patients”, and outlines how they are now described as eyewear: a fashionable accessory.[60] Much like other fashion designs and accessories, eyewear is created by designers, has reputable labels, and comes in collections, by season and designer.[60] In recent years, it has become more common for consumers to purchase eyewear with non-prescription lenses as a fashion accessory.[60]
The market for spectacles has been characterized as having highly inelastic demand. Advertising restrictions in the United States, for example, have correlated with higher prices, suggesting that adverts make the spectacles market more price-competitive.[61] It has also been claimed to be monopolistically competitive, as in the case of Luxottica.[62][63][64]
There are claims that insufficiently free market competition inflates the prices of frames, which cost an average of $25–$50 U.S. to make, to an average retail price of $300 in the United States. This claim is disputed by some in the industry.[65][66][67]
The United States also prohibits the sale of glasses unless the user has a recent prescription from an optometrist or ophthalmologist, whereas in most of the world, glasses and contact lenses can be bought without needing to get a new eye exam first.[68] This means that Americans who lose or break their glasses may be unable to see well until they can get, and pay for, an appointment with an optometrist.[68] In most of the world, someone who has lost their glasses merely goes to the nearest store selling glasses and buys a replacement over the counter.[68]
Many people require glasses for the reasons listed above. There are many shapes, colors, and materials that can be used when designing frames and lenses that can be utilized in various combinations. Oftentimes, the selection of a frame is made based on how it will affect the appearance of the wearer. Some people with good natural eyesight like to wear eyeglasses as a style accessory. In Japan, some companies ban women from wearing glasses.[73]
For most of their history, eyeglasses were seen as unfashionable, and carried several potentially negative connotations: wearing glasses caused individuals to be stigmatized and stereotyped as pious clergymen, as those in religious vocation were the most likely to be literate and therefore the most likely to need reading glasses, elderly, or physically weak and passive.[74][75] The stigma began to fall away in the U.S. in the early 1900s when the popular Theodore Roosevelt was regularly photographed wearing eyeglasses, and in the 1910s when popular comedian Harold Lloyd wore a pair of horn-rimmed glasses as the “Glasses” character in his films.[74][75]
In the United Kingdom, wearing glasses was characterized in the nineteenth century as “a sure sign of the weakling and the mollycoddle”, according to Neville Cardus, writing in 1928.[76]“Tim” Killick was the first professional cricketer to play while wearing glasses “continuously”, after his vision deteriorated in 1897. “With their aid he placed himself in the forefront among English professionals of all-round abilities.”[76] The American tenor Jan Peerce, plagued with poor eyesight, credited comedian Steve Allen for normalizing and even popularizing the wearing of eyeglasses in front of live television and stage audiences; prior to this, performers who read on early television were expected to squint or use contact lenses.[77]
Since then, eyeglasses have become an acceptable fashion item and often act as a key component in individuals’ personal image. Musicians Buddy Holly and John Lennon became synonymous with the styles of eye-glasses they wore to the point that thick, black horn-rimmed glasses are often called “Buddy Holly glasses” and perfectly round metal eyeglass frames called “John Lennon glasses” (or, more recently, “Harry Potter glasses”). British comedic actor Eric Sykes was known in the United Kingdom for wearing thick, square, horn-rimmed glasses, which were in fact a sophisticated hearing aid that alleviated his deafness by allowing him to “hear” vibrations.[78] Some celebrities have become so associated with their eyeglasses that they continued to wear them even after taking other measures against vision problems: U.S. Senator Barry Goldwater and comedian Drew Carey continued to wear non-prescription glasses after being fitted for contacts and getting laser eye surgery, respectively.
In superhero fiction, eyeglasses have become a standard component of various heroes’ disguises as masks, allowing them to adopt a nondescript demeanor when they are not in their superhero personae: Superman is well known for wearing 1950s-style horn-rimmed glasses as Clark Kent, while Wonder Woman wears either round, Harold Lloyd-style glasses or 1970s-style bug-eye glasses as Diana Prince. An example of the halo effect is seen in the stereotype that those who wear glasses are intelligent. This belief can have positive consequences for people who wear glasses, for example in elections. Studies show that wearing glasses increases politicians’ electoral success, at least in Western cultures.[81]
In the 20th century, eyeglasses came to be considered a component of fashion; as such, various different styles have come in and out of popularity. Most are still in regular use, albeit with varying degrees of frequency.
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