Glass production involves two main methods – the float glass process that produces sheet glass, glassblowing that produces bottles and other containers. Broadly, modern glass container factories are three-part operations: the batch house, the hot end, the cold end; the batch house handles the raw materials. The following table lists common viscosity fixpoints, applicable to large-scale glass production and experimental glass melting in the laboratory: Batch processing is one of the initial steps of the glass-making process; the batch house houses the raw materials in large silos and holds anywhere from 1–5 days of material. Some batch systems include material processing such as raw material screening/sieve, drying, or pre-heating. Whether automated or manual, the batch house measures, assembles and delivers the glass raw material recipe via an array of chutes and scales to the furnace; the batch enters the furnace at the'dog house' or'batch charger'. Different glass types, desired quality, raw material purity / availability, furnace design will affect the batch recipe.
The hot end of a glassworks is where the molten glass is formed into glass products, beginning when the batch is fed into the furnace at a slow, controlled rate by the batch processing system. The furnaces are natural gas- or fuel oil-fired, operate at temperatures up to 1,575 °C; the temperature is limited only by the quality of the furnace’s superstructure material and by the glass composition. Types of furnaces used in container glass making include'end-port','side-port', and'oxy-fuel'. Furnace "size" is classified by metric tons per day production capability. There are two primary methods of making glass containers: the blow & blow method for narrow-neck containers only, the press & blow method used for jars and tapered narrow-neck containers. Figure 1: Steps during Blow&Blow container forming process In both methods, a stream of molten glass, at its plastic temperature, is cut with a shearing blade to form a solid cylinder of glass, called a gob; the gob is of predetermined weight just sufficient to make a bottle.
Both processes start with the gob falling, by gravity, guided, through troughs and chutes, into the blank moulds, two halves of which are clamped shut and sealed by the "baffle" from above. In the blow and blow process, the glass is first blown through a valve in the baffle, forcing it down into the three-piece "ring mould", held in the "neckring arm" below the blanks, to form the "finish", The compressed air is blown through the glass, which results in hollow and formed container. Compressed air is blown again at the second stage to give final shape. Containers are made in two major stages; the first stage moulds all the details around the opening, but the body of the container is made much smaller than its final size. These manufactured containers are called parisons, quite they are blow-molded into final shape. Referring to the mechanism, the "rings" are sealed from below by a short plunger. After the "settleblow" finishes, the plunger retracts to allow the skin that's formed to soften. "Counterblow" air comes up through the plunger, to create the parison.
The baffle rises and the blanks open. The parison is inverted in an arc to the "mould side" by the "neckring arm", which holds the parison by the "finish"; as the neckring arm reaches the end of its arc, two mould halves close around the parison. The neckring arm opens to release its grip on the "finish" reverts to the blank side. Final blow, applied through the "blowhead", blows the glass out, expanding into the mould, to make the final container shape. In the press and blow process, the parison is formed by a long metal plunger which rises up and presses the glass out, in order to fill the ring and blank moulds; the process continues as before, with the parison being transferred to the final-shape mould, the glass being blown out into the mould. The container is picked up from the mould by the "take-out" mechanism, held over the "deadplate", where air cooling helps cool down the still-soft glass; the bottles are swept onto a conveyor by the "push out paddles" that have air pockets to keep the bottles standing after landing on the "deadplate".
The forming machines move the parts that form the container. The machine consist of basic 19 mechanisms in operation to form a bottle and powered by compressed air, the mechanisms are electronically timed to coordinate all movements of the mechanisms; the most used forming machine arrangement is the individual section machine. This machine has a bank of 5–20 identical sections, each of which contains one complete set of mechanisms to make containers; the sections are in a row, the gobs feed into each section via a moving chute, called the gob distributor. Sections make either one, three or four containers simultaneously.. In the case of multiple gobs, the shears cut the gobs and they fall into the blank moulds in parallel. After the forming process, some containers—particularly those intended for alcoholic spirits—undergo a treatment t
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events. The formation of similar features during explosive volcanism is discounted due to the lack of metamorphic effects unequivocally associated with explosions and the difficulty in reaching sufficient pressures during such an event. Planar fractures are parallel sets of multiple planar cleavages in quartz grains. Although the occurrence of planar fractures is common in other deformed rocks, the development of intense and spaced planar fractures is considered diagnostic of shock metamorphism. Planar deformation features, or PDFs, are optically recognizable microscopic features in grains of silicate minerals, consisting of narrow planes of glassy material arranged in parallel sets that have distinct orientations with respect to the grain's crystal structure. PDFs are only produced by extreme shock compressions on the scale of meteor impacts, they are not found in volcanic environments.
This form of twinning in quartz is common but the occurrence of close-spaced Brazil twins parallel to the basal plane, has only been reported from impact structures. Experimental formation of basal-orientated Brazil twins in quartz requires high stresses and high strain rates, it seems probable that such features in natural quartz can be regarded as unique impact indicators; the high pressures associated with impacts can lead to the formation of high-pressure polymorphs of various minerals. Quartz may occur as either of its two high-pressure forms and stishovite. Coesite occurs associated with eclogites formed during high pressure regional metamorphism but was first discovered in a meteorite crater in 1960. Stishovite, however, is only known from impact structures. Two of the high-pressure polymorphs of titanium dioxide, one with a baddeleyite-like form and the other with a α-PbO2 structure, have been found associated with the Nördlinger Ries impact structure. Diamond, the high-pressure allotrope of carbon, has been found associated with many impact structures, both fullerenes and carbynes have been reported.
Shatter cones have a distinctively conical shape that radiates from the top of the cones repeating cone-on-cone, at various scales in the same sample. They are only known to form in rocks beneath meteorite impact craters or underground nuclear explosions, they are evidence that the rock has been subjected to a shock with pressures in the range of 2-30 GPa. There exist macroscopic white lamellae inside quartz and other minerals in the Bohemian Massif and at other places around the world like wavefronts generated by a meteorite impact according to the Rajlich's Hypothesis; the hypothetical wavefronts are composed of many microcavities. Their origin is seen in a physical phenomenon of ultrasonic cavitation, well known from the technical practice; the effects described above have been found singly, or more in combination, associated with every impact structure, identified on Earth. The search for such effects therefore forms the basis for identifying possible candidate impact structures to distinguish them from volcanic features.
Impactite Meteorite shock stage Suevite Chapter 4,'Shock-Metamorphic Effects in Rocks and Minerals' of the online book, French, B. M. 1998. Traces of Catastrophe, A handbook of shock-metamorphic effects in terrestrial meteorite impact structures and Planetary Institute 120pp. Shock metamorphism page. Shatter cones page
The term blowpipe refers to one of several tools used to direct streams of gases into any of several working media. If a stream or jet of air is directed through a flame, fuel air mixing is enhanced and the jet exiting the flame is intensely hot. Jewelers and glassblowers engaged in lampwork have used the blowpipe since ancient times, with the blast being powered by the user's lungs. For small work, mouth-blown blowpipes may be used with candle flames or alcohol lamps. Starting in the 1800s, blowpipes have been powered by mechanisms bladders and bellows, but now blowers and compressed gas cylinders are commonplace. While blowing air is effective, blowing oxygen produces higher temperatures, it is practical to invert the roles of the gasses and blow fuel through air. Contemporary blowtorches and oxy-fuel welding and cutting torches can be considered to be modern developments of the blowpipe. In chemistry and mineralogy blowpipes have been used as scientific instruments for the analysis of small samples since about 1738, according to the accounts of Torbern Bergman.
One Andreas Swab, a Swedish metallurgist and Counsellor of the College of Mines is credited with the first use of the blowpipe for'pyrognostic operations', of which no record remains. The next person of eminence who used the blowpipe was Axel Fredrik Cronstedt, who put it to the purpose of the discrimination of minerals by means of fusible reagents. In 1770 an English translation of Cronstedt's work was made by Von Engestrom, annexed to, a treatise on the blowpipe. Despite this opening, assay by blowpipe was for the time an occupation undertaken for the most part in Sweden. Bergman's use of the blowpipe outstripped all of his predecessors, he widened its application from mineralogy to inorganic chemistry, giving rise to what may be regarded as a masterpiece of philosophical investigation, De Tubo Ferruminatorio, published in Vienna in 1779. Bergman's assistant, Assessor Gahn, is next credited with moving the design and application of the blowpipe on. Gahn travelled with a portable blowpipe, applying it to every kind of chemical and mineralogical enquiry, such as proving the presence of copper in the ashes of vegetables.
Gahn published a Treatise on the Blowpipe, reprinted a number of times in contemporary chemistry textbooks. Jöns Jakob Berzelius worked with Gahn to ascertain in a systematic manner of the phenomena presented by different minerals when acted on by the blowpipe, he established, according to Griffin, the notion that the blowpipe was an instrument of indispensable utility, his published work translated into English, was regarded as one of the most useful books on practical chemistry extant. The blowpipes of all of the foregoing blasted air into a flame; the blow pipe was used by the Egyptians to today. Antoine Lavoisier is credited as the first to blow oxygen - of which he was co-discoverer - through a blowpipe to support the combustion of charcoal, in 1782. Others, such as Edward Daniel Clarke, employed hydrogen, mixed hydrogen and oxygen in the oxy-hydrogen blowpipe; the vastly increased temperatures, the volatility of hydrogen-oxygen mixes drove on the development of the so-called gas blowpipe as a tool, at the same time brought many new materials into reach of the blowpipe as a tool for assay.
Robert Hare was a noted exponent of the improved tool. Goldsworthy Gurney, whilst at the Surrey Institute, published in 1823 an account of a new blowpipe so constructed as to enable the operator to produce a flame of great size and brilliancy by burning large quantities of the mixed gases with the utmost safety. Gurney went on to employ the principles in his Bude light. In glassblowing, the term blowpipe refers to a pipe used to blow a bubble of air into a gather of molten glass, as the first step in the creation of hand-blown glass bottles and bowls. By the end of the first century, the two primary glassblowing tools were the iron blowpipe and pontil. Glassblowing blowpipes are long enough to keep the gather of molten glass at a safe distance from the glassblower, rigid enough to support the weight of the glass when the pipe is held horizontally; the term blowpipe is used to refer to the pipe used to blow deliver air to the tuyeres of a forge or blast furnace. The blowpipe of a forge may be considered to be a large bellows operated version of a mouth-blown blowpipe, directing air through a coal or charcoal flame.
Blowpipes are known as blow pokers. They are used to stoke fires. Blowpipes are straight, tube-like tools used to direct oxygen to boost a wooden fire. Blowpipes have been in use for hundreds of years, but were first documented by John Griffin in his 1827 book A Practical Treatise on the Use of the Blowpipe. Blow pokers are multifunctional fire irons, they are used to arrange the embers or firewood in a wood fire, secondarily they are used as a blow pipe. The term "BlowPoker" was introduced in 2005 by the German company Red Anvil GmbH, a manufacturer of fire irons and fireside accessories, their BlowPoker has a plate to arrange the ashes. Since 2005 the term blow poker has established itself in the trade as a generic term for a multifunctional poker tool
Glass fiber is a material consisting of numerous fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling. In 1893, Edward Drummond Libbey exhibited a dress at the World's Columbian Exposition incorporating glass fibers with the diameter and texture of silk fibers. Glass fibers can occur as Pele's hair. Glass wool, one product called "fiberglass" today, was invented in 1932–1933 by Russell Games Slayter of Owens-Corning, as a material to be used as thermal building insulation, it is marketed under the trade name Fiberglas. Glass fiber when used as a thermal insulating material, is specially manufactured with a bonding agent to trap many small air cells, resulting in the characteristically air-filled low-density "glass wool" family of products. Glass fiber has comparable mechanical properties to other fibers such as polymers and carbon fiber. Although not as rigid as carbon fiber, it is much cheaper and less brittle when used in composites.
Glass fibers are therefore used as a reinforcing agent for many polymer products. This material contains little or no air or gas, is more dense, is a much poorer thermal insulator than is glass wool. Glass fiber is formed when thin strands of silica-based or other formulation glass are extruded into many fibers with small diameters suitable for textile processing; the technique of heating and drawing glass into fine fibers has been known for millennia. Until this time, all glass fiber had been manufactured as staple; the modern method for producing glass wool is the invention of Games Slayter working at the Owens-Illinois Glass Co.. He first applied for a patent for a new process to make glass wool in 1933; the first commercial production of glass fiber was in 1936. In 1938 Owens-Illinois Glass Company and Corning Glass Works joined to form the Owens-Corning Fiberglas Corporation; when the two companies joined to produce and promote glass fiber, they introduced continuous filament glass fibers.
Owens-Corning is still the major glass-fiber producer in the market today. The most common types of glass fiber used in fiberglass is E-glass, alumino-borosilicate glass with less than 1% w/w alkali oxides used for glass-reinforced plastics. Other types of glass used are A-glass, E-CR-glass, C-glass, D-glass, R-glass, S-glass. Pure silica, when cooled as fused quartz into a glass with no true melting point, can be used as a glass fiber for fiberglass, but has the drawback that it must be worked at high temperatures. In order to lower the necessary work temperature, other materials are introduced as "fluxing agents". Ordinary A-glass or soda lime glass and ready to be remelted, as so-called cullet glass, was the first type of glass used for fiberglass. E-glass, is alkali free, was the first glass formulation used for continuous filament formation, it now makes up most of the fiberglass production in the world, is the single largest consumer of boron minerals globally. It is a poor choice for marine applications.
S-glass is used when high tensile strength is important, is thus important in composites for building and aircraft construction. The same substance is known as R-glass in Europe. C-glass and T-glass are resistant to chemical attack; the basis of textile-grade glass fibers is silica, SiO2. In its pure form it exists as n, it softens up to 1200 °C, where it starts to degrade. At 1713 °C, most of the molecules can move about freely. If the glass is extruded and cooled at this temperature, it will be unable to form an ordered structure. In the polymer it forms SiO4 groups which are configured as a tetrahedron with the silicon atom at the center, four oxygen atoms at the corners; these atoms form a network bonded at the corners by sharing the oxygen atoms. The vitreous and crystalline states of silica have similar energy levels on a molecular basis implying that the glassy form is stable. In order to induce crystallization, it must be heated to temperatures above 1200 °C for long periods of time. Although pure silica is a viable glass and glass fiber, it must be worked with at high temperatures, a drawback unless its specific chemical properties are needed.
It is usual to introduce impurities into the glass in the form of other materials to lower its working temperature. These materials impart various other properties to the glass
Glass casting is the process in which glass objects are cast by directing molten glass into a mould where it solidifies. The technique has been used since the Egyptian period. Modern cast glass is formed by a variety of processes such as kiln casting, or casting into sand, graphite or metal moulds. During the Roman period, moulds consisting of two or more interlocking parts were used to create blank glass dishes. Glass could be added to the mould either by frit casting, where the mould was filled with chips of glass and heated to melt the glass, or by pouring molten glass into the mould. Evidence from Pompeii suggests that molten hot glass may have been introduced as early as the mid-1st century CE. Blank vessels were annealed, fixed to lathes and cut and polished on all surfaces to achieve their final shape. Pliny the Elder indicates in his Natural History that lathes were used in the production of most glass of the mid-1st century. Italy is believed to have been the source of the majority of early Imperial polychrome cast glass, whereas monochrome cast glasses are more predominant elsewhere in the Mediterranean.
Forms produced show clear inspiration from the Roman bronze and silver industries, in the case of carinated bowls and dishes, from the ceramic industry. Cast vessel forms became more limited during the late 1st century, but continued in production into the second or third decade of the 2nd century. Colourless cast bowls were widespread throughout the Roman world in the late 1st and early 2nd century CE, may have been produced at more than one centre; some revival of the casting technique appears in the 3rd or 4th century, but appears to have produced small numbers of vessels Sand casting involves the use of hot molten glass poured directly into a preformed mould. It is a process similar to casting metal into a mould; the sand mould is prepared by using a mixture of clean sand and a small proportion of the water-absorbing clay bentonite. Bentonite acts as a binding material. In the process, a small amount of water is added to the sand-bentonite mixture and this is well mixed and sifted before addition to an open topped container.
A template is prepared, pressed into the sand to make a clean impression. This impression forms the mould; the surface of the mould can be covered in coloured glass powders or frits to give a surface colour to the sand cast glass object. When the mould preparation is complete hot glass is ladled from the furnace at temperatures of about 1,200 °C to allow it to pour; the hot glass is poured directly into the mould. During the pouring process, glass or compatible objects may be placed to give the appearance of floating in the solid glass object; this immediate and dynamic method was pioneered and perfected in the 1980s by the Swedish artist Bertil Vallien. Kiln casting involves the preparation of a mould, made of a mixture of plaster and refractory materials such as silica. A model can be made from any solid material, such as wax, wood, or metal, after taking a cast of the model the model is removed from the mould. One method of forming a mould is by "lost wax" method. Using this method, a model can be made from wax and after investment the wax can be steamed or burned away in a kiln, forming a cavity.
The heat resistant mould is placed in a kiln equipped with a funnel-like opening filled with solid glass granules or lumps. The kiln is heated to between 800 °C and 1,000 °C, as the glass melts it runs into and fills the mould; such kiln cast work can be of large dimensions, as in the work of Czechoslovakian artists Stanislav Libensky and Jaroslava Brychtova. Kiln cast glass has become an important material for contemporary artists such as Clifford Rainey, Karen LaMonte and Tomasz Urbanowicz. Pâte de verre is a form of kiln casting and translated means glass paste. In this process, finely crushed glass is mixed with a binding material, such as a mixture of gum arabic and water, with colourants and enamels; the resultant paste is applied to the inner surface of a negative mould forming a coating. After the coated mould is fired at the appropriate temperature the glass is fused creating a hollow object that can have thick or thin walls depending on the thickness of the pate de verre layers. Daum, a French commercial crystal manufacturer, produce sculptural pieces in pate de verre.
Graphite is used in the hot forming of glass. Graphite moulds are prepared by carving into them, machining them into curved forms, or stacking them into shapes. Molten glass is poured into a mould where it is cooled until hard enough to be removed and placed into an annealing kiln to cool slowly. Glass art Amalric Walter Cummings, Keith. Techniques of Kiln-formed Glass. University of Pennsylvania Press. Pp. 84–85. ISBN 978-0-8122-3402-2
An optical fiber is a flexible, transparent fiber made by drawing glass or plastic to a diameter thicker than that of a human hair. Optical fibers are used most as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than electrical cables. Fibers are used instead of metal wires. Fibers are used for illumination and imaging, are wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors and fiber lasers. Optical fibers include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, while those that support a single mode are called single-mode fibers.
Multi-mode fibers have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters. Being able to join optical fibers with low loss is important in fiber optic communication; this is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the fiber cores, the coupling of these aligned cores. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a mechanical splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors; the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics.
The term was coined by Indian physicist Narinder Singh Kapany, acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London, 12 years later. Tyndall wrote about the property of total internal reflection in an introductory book about the nature of light in 1870:When the light passes from air into water, the refracted ray is bent towards the perpendicular... When the ray passes from water to air it is bent from the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be reflected at the surface.... The angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, while for diamond it is 23°42′.
In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate body cavities. Practical applications such as close internal illumination during dentistry appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. In the 1930s, Heinrich Lamm showed that one could transmit images through a bundle of unclad optical fibers and used it for internal medical examinations, but his work was forgotten. In 1953, Dutch scientist Bram van Heel first demonstrated image transmission through bundles of optical fibers with a transparent cladding; that same year, Harold Hopkins and Narinder Singh Kapany at Imperial College in London succeeded in making image-transmitting bundles with over 10,000 fibers, subsequently achieved image transmission through a 75 cm long bundle which combined several thousand fibers. Their article titled "A flexible fibrescope, using static scanning" was published in the journal Nature in 1954.
The first practical fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers. A variety of other image transmission applications soon followed. Kapany coined the term fiber optics, wrote a 1960 article in Scientific American that introduced the topic to a wide audience, wrote the first book about the new field; the first working fiber-optical data transmission system was demonstrated by German physicist Manfred Börner at Telefunken Research Labs in Ulm in 1965, followed by the first patent application for this technology in 1966. NASA used fiber optics in the television cameras. At the time, the use in the cameras was classified confidential, employees handling the cameras had to be supervised by someone with an appropriate security clearance. Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables were the first, in 1965, to promote the idea that the attenuation in optical fibers could be reduced below 20 decibels per kilometer, making fibers a practical communication medium.
They proposed th
In glassblowing, cane refers to rods of glass with color. Caneworking refers to the process of making cane, to the use of pieces of cane, lengthwise, in the blowing process to add intricate spiral and stripes to vessels or other blown glass objects. Cane is used to make murrine, thin discs cut from the cane in cross-section that are added to blown or hot-worked objects. A particular form of murrine glasswork is millefiori, in which many murrine with a flower-like or star-shaped cross-section are included in a blown glass piece. Caneworking is an ancient technique, first invented in southern Italy in the second half of the third century BC, elaborately developed centuries on the Italian island of Murano. There are several different methods of making cane. In each, the fundamental technique is the same: a lump of glass containing some pattern of colored and clear glass, is heated in a furnace and pulled, by means of a long metal rod attached at each end; as the glass is stretched out, it retains whatever cross-sectional pattern was in the original lump, but narrows quite uniformly along its length.
Cane is pulled until it reaches the diameter of a pencil, depending on the size of the original lump, it may be anywhere from one to fifty feet in length. After cooling, it is broken into sections from four to six inches long, which can be used in making more complex canes or in other glassblowing techniques; the simplest cane, called vetro a fili is clear glass with one or more threads of colored glass running its length. It is made by heating and shaping a chunk of clear, white, or colored glass on the end of a punty, ‘’gathering’’ molten clear glass over the color by dipping the punty in a furnace containing the clear glass. After the desired amount of clear glass is surrounding the color, this cylinder of hot glass is shaped and heated until uniform in shape and temperature. An assistant prepares a'post', another punty with a small platform of clear glass on the end; the post is pressed against the end of the hot cylinder of glass to connect them, the glassblower and assistant walk away from each other with the punties, until the cane is stretched to the desired length and diameter.
The cane is cut into small sections. A simple single-thread cane can be used to make more complex canes. A small bundle of single-thread canes can be heated until they fuse, or heated canes, laid parallel, can be picked up on the circumference of a hot cylinder of clear or colored glass; this bundle, treated just as the chunk of color in the description above, is cased in clear glass and pulled out, forming a vetro a fili cane with multiple threads and a clear or solid color core. If the cane is twisted as it is pulled, the threads take a spiral shape called vetro a retorti or zanfirico. Ballotini is a cane technique in which several vetro a fili canes are picked up while laid side-by-side rather than a bundle, with a clear glass gather over them; this gather is shaped into a cylinder with the canes directed along the axis, so that the canes form a sort of “fence” across the diameter of the cylinder. When this is twisted and pulled, the resulting cane has a helix of threads across its thickness.
Another technique for forming cane is to use optic molds to make more complex cross sections. An optic mold is an open-ended cone-shaped mold with some sort of lobed or star shape around its inside circumference; when a gather or blown bubble is forced into the mold, its outside takes the shape of the mold. Canes with complicated, multi-colored patterns are formed by placing layers of different or alternating colors over a solid-color core, using various optic molds on the layers as they are built; because the outer layers are hotter than those inside when the molds are used, the mold shape is impressed into the outer color without deforming the inner shapes. Canes made in this way are used in making millefiori. Discs from eight different canes have been used to make the pendant in the photo. Flameworkers sometimes make cane by building up the cross-section using ordinary flameworking or bead making techniques; this permits subtle gradations of color and shading, is the way murrine portraits are made.
The generic term for blown glass made using canes in the lengthwise direction is filigrano, as contrasted with murrine when the canes are sliced and used in cross-section.. One way glassblowers incorporate cane into their work is to line up canes on a steel or ceramic plate and heat them to avoid cracking; when the surfaces of the canes just begin to melt, the canes adhere to each other. The tip of a glassblowing pipe is covered with a'collar' of clear molten glass, touched to one corner of the aligned canes; the tip of the blowpipe is rolled along the bottom of the canes, which stick to the collar, aligned cylindrically around the edge of the blowpipe. They are heated further until soft enough to shape; the cylinder of canes is sealed at the bottom with jacks and tweezers, to form the beginning of a bubble. The bubble is blown using traditional glassblowing techniques