Abstract: A method and apparatus for forming a glass parison are disclosed. A glass parison forming apparatus includes a feeder spout having an orifice ring, a plunger carried in the feeder spout and including a blow conduit therethrough, and a neck ring located immediately downstream of the orifice ring, with no chutes, scoops, or other gob handling devices therebetween. A glass container produced by the disclosed method and apparatus is also described.

Abstract: One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

Abstract: The method for manufacturing a hollow glass article comprises the following steps: introducing a blank (38) of the article into a finishing mold (26), and forming the article in the finishing mold (26), by injecting at least one gas and a forming pressure inside the blank (38) of the article. During formation of the article in the finishing mold (26), at least one gas injection point (54A) is displaced for directing the gas towards at least one predefined area of the blank (38), the gas being injected at least at a finishing pressure in order to form a specific inner glass distribution of the article.

Abstract: A structure printer for printing structures that has a stable platform on which a swiveling base is mounted. A boom is extendible from the base having a plasmatron mounted on the end of the boom for heating and melting the building material, which may subsequently be sprayed by a print head that receives the molten material from the plasmatron, the print head having an adjustable nozzle for expelling the mixture in a specific location. The printer may be vehicle-mounted, and may have a computer control so it is able to print a building faithfully from a blueprint. The building material may be foam glass, or other mixtures may be used.

Abstract: Systems and methods for processing lead-containing glass are generally described. In certain embodiments, at least a portion of the lead within the bulk of the lead-containing glass is removed from the lead-containing glass and transferred to a liquid leaching medium. Removal of lead from the bulk of the lead-containing glass, as opposed to the surface and areas closely adjacent to the surface of the lead-containing glass, can allow for the production of recycled glass that includes substantially no lead within its boundaries.

Abstract: An layout for a glass manufacturing system may include a hot process part having a batch plant for storing a glass raw material, a tank for melting the raw material and storing a molten glass, a float bath for forming the molten glass into a glass of a ribbon shape, an annealing lehr for cooling the glass ribbon, and a cold end connected to the annealing lehr, and an etching process part having a final cutting sector for cutting the glass provided from the cold end into sheet glasses of a preset final size, a beveling and etching sector for bevel the edges of the cut sheet glasses and etching the beveled sheet glasses, and a first inspection sector for inspecting the etched sheet glasses, and the hot process part and the etching process part may be connected by a single conveyor to form a continuous line.

Abstract: Ion transport membranes are integrated with a glass melting furnace and a float glass bath. Only feeds of air, steam and hydrocarbon are necessary for producing hot oxygen for the melting furnace and a mixture of nitrogen, carbon dioxide, and hydrogen for the float glass bath.

Abstract: Melters for glass forming apparatuses and glass forming apparatuses comprising the same are disclosed. According to one embodiment, a melter for melting glass batch materials includes a base portion and a rigid exoskeleton rigidly attached to the base portion and comprising a plurality of upright members interconnected with a plurality of cross members defining an exoskeleton interior volume. Connection nodes formed at intersections of the plurality of cross members with upper ends of the plurality of upright members are constrained from movement relative to the base portion in a longitudinal direction, a transverse direction, and a vertical direction. A tank assembly is positioned on the base portion in the exoskeleton interior volume and coupled to the rigid exoskeleton. In some embodiments, the melter has a dynamic resistance greater than 0.3.

Abstract: An apparatus for chemically toughening glass which can toughen the surface of the glass by inducing compressive stress on the glass surface through ion exchange and a method of chemically toughening glass using the same. The apparatus includes a chemical toughening bath which chemically toughens the glass; a transportation part which transports the glass from upstream of the chemical toughening bath through the chemical toughening bath to downstream of the chemical toughening bath; and a microwave generator disposed above the chemical toughening bath, the microwave generator radiating microwaves to the glass.

Abstract: Systems and methods for processing lead-containing glass are generally described. In certain embodiments, at least a portion of the lead within the bulk of the lead-containing glass is removed from the lead-containing glass and transferred to a liquid leaching medium. Removal of lead from the bulk of the lead-containing glass, as opposed to the surface and areas closely adjacent to the surface of the lead-containing glass, can allow for the production of recycled glass that includes substantially no lead within its boundaries.

Abstract: A precious metal structure which has an internal gas permeable membrane is described herein for a glass manufacturing vessel configured to have molten glass flow therein. The internal gas permeable membrane can be supplied with an atmosphere of gas (or gases) to control the flux of hydrogen into our out of the molten glass or otherwise improve the production of the molten glass. In this manner, the undesirable detrimental reactions that can occur at the interface of the molten glass and precious metal interface which can cause defects in the molten glass such as bubbles or solid inclusions can be stopped or at least substantially reduced.

Abstract: A process for manufacturing a vitreous slag including rotating a cone about a vertical cone axis, the cone including an external shell having a lateral surface; cooling the lateral surface of the external shell; pouring molten slag onto the lateral surface of the cone to form a film of slag by gravity, which is solidified as it is entrained in rotation by the cone about the cone axis; and detaching pieces of the film from the lateral surface and removing solidified slag in the form of the pieces after the film has been entrained through between 0.6 and 0.9 revolutions of the cone, the molten slag being poured onto the lateral surface in a pouring zone and spreads to form a film over substantially the entire length of the lateral surface, preferably over between 75% and 95% of the length of the lateral surface.

Abstract: An apparatus and method for removing volatilized chemical compounds from within enclosed or partially enclosed spaces containing molten glass. One or more condensing devices are positioned within the enclosure to produce preferential condensation of the vapor on condensing elements of the condensing devices, thereby facilitating easy removal of the condensates from the enclosure. The condensing elements may have a variety of shapes and sizes depending on the design of the enclosure.

Abstract: A method of improving the stain resistance of a surface of a glass article such as a float glass ribbon or float glass sheet is disclosed. The method comprises the steps of (i) applying a solution comprising a stain inhibitor to an absorbent strip; (ii) transferring solution from the wet strip to the surface of the glass article; and (iii) drying the wet glass surface to leave stain inhibitor on the surface of the glass article. A facility for manufacturing the glass article incorporating an apparatus for applying a solution comprising a stain inhibitor to the surface of the glass article in accordance with the aforementioned method is also disclosed.

Abstract: An oblong conduit (13) for conditioning molten glass is disclosed. The wall (23) of the conduit is composed of a precious metal, e.g., a platinum-rhodium alloy, and can be equipped with precious metal tabs (29) for supporting the upper surface (25) of the wall so as to reduce sag of that surface at such times as the conduit is at an elevated temperature and is not filled with glass. The precious metal tabs (29) can be received in channels (31) formed in a refractory support structure (27). The refractory support structure (27) can be a laminate of two layers (33,35), where one of the layers (33) has a smaller grain structure than the other layer (35), the layers being held together by an adhesive (37).

Abstract: An apparatus for drawing a glass ribbon including a shroud surrounding the glass ribbon and an edge roll that penetrates the shroud to contact the glass ribbon. The apparatus includes regulating a pressure within the seal assembly to be equal to or less than a pressure within the shroud and prevent ingress of relatively cooler outside gas into the hot interior of the shroud. The edge roll utilizes an air bearing to minimize friction that can produce periodic fluctuation of the ribbon as the edge roll is displaces in response to variations in the ribbon thickness or equipment dimensions.

Abstract: Methods and apparatus for refining and delivering a supply of molten glass include melting a supply of glass in a melter and discharging a stream of molten glass. A refining section is provided to refine the molten glass discharged by the melter and to deliver the molten glass downstream to a glass forming apparatus. The refining section is mounted for movement into and out of contact with the stream of molten glass to connect and disconnect the glass forming apparatus with the stream of molten glass.

Abstract: The present invention relates to a glass meting furnace comprising a channel-shaped melting tank, the batch materials being introduced at an upstream end, the molten glass being recovered at the downstream end, said furnace being heated by means of burners, in which the combustion energy is produced by oxy-fuel combustion in respect of at least 65% thereof, the burners being distributed on the walls along the length of the furnace, in which flue gas discharge is mostly localized close to the upstream end near the openings through which the batch materials are introduced, the rest of the flue gas being removed close to the downstream part so as to maintain dynamic sealing with respect to the surrounding atmosphere.

Abstract: Provided is a heat treatment apparatus for tempering glass capable of stabilizing quality and increasing productivity by inducing a stability and smoothness between processes during automatically performing of a heat treatment operation for the tempered surface of thin plate type glass, and including a preheating furnace, a main body furnace, and a cooling furnace, the apparatus including: a traveling unit for moving a conveying bogie on a pair of rails installed in parallel on the preheating furnace, the main body furnace, and the cooling furnace; a rack elevating unit for stably performing an up and down motion of a rack in which the thin plate type glass included in the conveying bogie is accommodated; and a muffle disposed on the main body furnace and performing an indirect heating operation.

Abstract: A method for forming shaped articles (28?) includes preparing a stack (26) having at least an adjacent set (27) of preformed material (28) and forming mold (30), where the preformed material (28) has an edge portion (34) that extends beyond a periphery of the forming mold (30), and the forming mold (30) has an external surface (32) with a desired surface profile of a shaped article. The stack (28) is heated. The stack (28) is advanced through a constriction (56) that has an internal surface configured to fold the edge portion (34) of the preformed material (28) into contact with the external surface (32) of the forming mold (30) as the edge portion (34) passes through the constriction (56), thereby forming a shaped article (28?) from the preformed material (28). The shaped article (28?) is then separated from the forming mold (30).

Abstract: The present invention relates to a heating apparatus for glass-sheet-forming, which prevents formation of a heater distortion in a portion of a glass sheet facing to a temperature-distributing heat shield.

Abstract: The invention relates to a method for melting vitrifiable materials in a low-capacity oven, wherein at least part of the melting energy is supplied by two oxy-burners projecting into the melting chamber through the upstream wall and arranged on opposite sides of a vertical plane in which a longitudinal axis of the melting chamber is situated, in such a way as to create two flames, the respective injection axes thereof crossing at a distance from the upstream wall, between ? and ¾ of the length L of the melting chamber.

Abstract: An apparatus for manufacturing a float glass, including a float bath for strong a molten metal on which a molten glass flows, wherein the molten metal flows in the float bath, comprises a plurality of discharge slits formed through a wall of a downstream end of the float bath to discharge a molten metal crashing against the wall and dross floating on the molten metal; a flow-back channel formed in a widthwise direction of the float bath and communicated with the discharge slits; and a dross collecting member for collecting the dross flowing through the flow-back channel.

Abstract: A glass melting installation and a method of operation of this with a melting tank, with burners for fossil fuels and with at least one regenerator for preheating oxidation gases, whereby between the at least one regenerator and the melting tank at least two step-free port necks are provided for the alternating supply of oxidation gases and the removal of combustion gases, and whereby the port necks are provided with lateral supply openings for the supply of secondary oxidation gases. In order to achieve injection into the waste gas flow without directional influence, with a simple construction and good energy usage, the supply openings for the supply of secondary oxidation gases are perpendicular to the free cross-section of the port necks above the step-free bottom surfaces.

Abstract: A method and machine for obtaining bent glass sheets. Glass sheets are brought to their softening temperature, then they are caused to travel over a shaping bed of advancing elements for advancing them which are arranged along a path having a circular arc-shaped profile, the sheets progressively assuming their shape on entering the bed and over a first shaping zone, then being hardened by tempering or cooling in a second zone of the bed until they leave, and then the bent glass sheets thus obtained are recovered. The shaping bed is produced with a profile extending in a circular arc of more than 90°, and, on leaving the shaping bed, the hardened glass sheets are moved in a direction opposite that in which they were fed in.

Abstract: A convection heating furnace for a glass sheet, into which oven glass sheet (3) arrives along a hauling track, as on moving rolls (4), and said furnace further comprises of heating elements (12), in order to heat the air, which is blasted against glass sheet (3), a blaster and blast air channelling in order to blast said air against the glass sheet, and the blast air channelling has, elongated channels (1), into which at least a part of the blast air heating elements 12 are fitted, and each channel comprises air blasting means on its flank directed against the glass sheet (3). As air blast elements there are nozzle groups fixed on the channel (1) flank, where the nozzle group formed of sheet metal, as of two, into shape formed sheets joined together to form a casing, whereby said casing comprises one or several for blast air directed discharge channels (6), and the direction of air flow in said casing (2) is essentially in the same direction as in said discharge channels (6).

Abstract: The conservation of energy in the glass industries via the use of heat shields to decrease the amount of energy lost during transportation from the forming process to the annealing process. For maximum effectiveness, the thermal shields are made of materials whose surface has an emissivity of, but not limited too, less than 0.3. They are mounted from, or adjacent to, the means of conveyance of the glass material such that their use will not prohibit the normal production of such glass product. Their installation shall include the means for quick removal or relocation in case of production upsets. The heat shields reflect the radiant energy that is emitted from the high temperature glass back onto itself, and adjacent products, in a manner such as to reduce the loss of energy from such product that may subsequently be necessary for the annealing process.

Abstract: The present invention relates to an apparatus and a method for dyeing glass and, more particularly, an apparatus and a method, by which both surfaces of hot sheet-like glass may be dyed simultaneously and/or the surface containing tin residues of the sheet glass may be dyed to have a different colour than the surface without tin residues. The apparatus of the invention may be used for dyeing both sheet glass and utility glass, such as glass beakers.

Abstract: A method and system that uses a cold wall furnace for melting the materials that are feed into the furnace. In one aspect, at least a portion of the exterior surface of the cold wall furnace is surrounded by at least one jacket configured to transfer heat away from the metal liner of the furnace. This cooling causes the molten glass to solidify on the metal surface of the metal liner of the cold wall furnace, which acts to protect the metal liner of the furnace from oxidation during molten glass evacuation and subsequent exposure to atmosphere.

Abstract: The invention includes a method and system for heating one or more ingredients of a glass batch or the entire glass batch that is then used to make molten glass using waste hot gases from a system for generating electricity using a drive for an electrical generator that is powered by a heat engine that exhaust waste hot gases having a temperature of at least about 200 degrees C. At least a portion of the electricity generated can be used to power manufacturing plant equipment and the waste hot exhaust gases exhausted by the heat engine, such as a gas turbine, is used in a static or dynamic heat exchanger to heat the entire glass batch or one or more of the ingredients of the glass batch, prior to feeding the glass batch into a glass melting furnace.

Abstract: Methods for fabricating an optical film characterizable by a relationship between gain and thickness to prism pitch ratio (S/p) that varies cyclically are described. The thickness and the prism pitch of the optical film are selected based on the relationship between gain and S/p ratio, to obtain a desired gain. The optical film is formed having the S/p ratio that provides the desired gain.

Abstract: In a method of producing a glass gob by continuously dropping a molten glass 9 from a nozzle 2 in a dropping direction, a gas flow 20 is caused to continuously flow in the dropping direction along an outer peripheral surface of the nozzle 2 at a predetermined flow rate. The gas flow 20 applies a wind pressure to the molten glass 9 appearing from a nozzle end 2a of the nozzle 2 to drop the molten glass 9.

Abstract: The method of the present invention overcomes the hot-sticking problems between an inorganic non-metallic material (=insulator) to be molded and a forming die by maintaining an assembly comprising a forming die and the insulator in a polarized state during molding. Processes using said method lead to an improved surface quality of the molded insulator. A device for reducing said hot-sticking comprises a die (2) which acts as conductor, an electrode (3) which may act as support for the insulator (1) to be molded, means (5) for polarizing the assembly of said conductor, insulator and electrode which means (5) are connected by live electric wires (4) with said die and electrode.

Abstract: A crucible with 22 inches or more in inner diameter, which has a small deformation of the body under exposure to abundant heat radiation during pulling a single crystal, and which has no practical problem, and a method of producing the same are disclosed.

Abstract: A device for the formation, by pyrolysis, of a coating composed of metal or a metal compound on a face of a hot glass substrate which is in motion by bringing the face into contact with a gaseous reagent, includes a vault; support device for conveying the hot glass substrate along a path through a coating chamber defined between the vault and the face; device for supplying and distributing gaseous reagent to the coating chamber as a flow; and device for discharging exhaust gas from the coating chamber. The device for supplying and distributing gaseous reagent includes an ejection nozzle having defined therein a slot which opens directly into the coating chamber and has longitudinal internal walls which are substantially parallel to each other. The ejection nozzle has longitudinal internal walls which define a continuous convergent path which terminates at and communicates with the slot and which has an angle of convergence (.alpha.), thereby causing the flow of gaseous reagent to conform to the slot.

Abstract: A device for the formation, by pyrolysis, of a coating on a face of a hot glass substrate includes a vault; support elements for conveying the substrate along a path through a coating chamber defined between the main vault and the substrate; elements for supplying and distributing gaseous reagent to the coating chamber; elements for discharging exhaust gas from the coating chamber; and a plurality of struts. The elements for supplying and distributing gaseous reagent to the coating chamber include an ejection nozzle having defined therein a slot which opens directly into the coating chamber, has opposing longitudinal internal walls, extends transverse to the path of the substrate, and has a length which is substantially equal to the coating width of the coating formed. The plurality of struts are positioned at spaced intervals and connect the opposing walls of the slot together to thereby maintain the walls of the slot in substantially parallel disposition.

Abstract: An apparatus is presented for economically making crystallized glass products from waste ash produced from the sewage sludge dewatered by organic matters, which is usually regarded to be difficult to process. The melting is performed in two furnaces: the primary melting furnace and the secondary melting furnace. The primary furnace melts waste ash and the primary melt is charged into the secondary melting furnace. The glassy material produced in the secondary melting furnace is charged into a crystallization furnace to convert the glassy material to a crystallized glass product. This basic configuration of the apparatus allows the production of either irregular shaped crystallized products, such as crushed stone like products, or crystallized manufactured products, such as tiles and blocks, depending on the combination of processing equipment and their operating conditions.

Abstract: A method for manufacturing a preform having steps of obtaining a plastic material by kneading silica powder, a binder, water, and a surfactant, and obtaining a porous preform by extrusion-molding the plastic material.

Abstract: A method for preparing a ceramic article comprising compacting a particulate including a primary oxide and a secondary oxide to form a blank. The primary oxide is ZRO.sub.2 and the secondary oxide is MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides or a combination thereof. The blank is sintered in contact with MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides or a combination thereof. The zirconia alloy ceramic articles produced have a cubic phase case and a tetragonal phase core.

Abstract: For the production of a composite glass powder of any particle size from a fine particle size, multi-component mixture of a low-melting glass powder, fillers, and additives, the fine particle size, multicomponent mixture is sintered for 10-60 minutes at a temperature at which the base glass has a viscosity of 10.sup.5 to 10.sup.6.5 dPas, and the resultant sintered cake is ground to a powder of the desired particle size. If the multicomponent mixture comprises components decomposable with the release of gas, e.g., copper carbonate, the latter are decomposed prior to sintering at a temperature below the sintering temperature. The resultant composite glass powder containing copper oxide can be used for coating varistors.

Abstract: A convenient method of producing porous silica particles is disclosed. The particles produced by the method can have impurity levels in the parts-per-billion range, and can have substantially uniform size. The particles are advantageously used to produce silica-containing glass bodies such as optical fiber preforms, silica tubes, lenses, rods and the like. The method comprises forming a silica-containing sol in comminution device or forming such a sol and introducing it into a comminution device, causing a gel to form from the sol, and comminuting the gel in the comminution device such that substantially dry, porous particles result.

Abstract: A thick glass coating protects fluorescent or phosphorescent pigment particles from greying or fading due to service conditions, such as photochemical reactions. The pigment particles are mixed with a finely ground heavy metal-free glass in a ratio of approximately 5 parts glass to 1 part pigment. The pigment and glass mixture is then heated to a point where said glass is softened to such an extent that the pigment particles are surrounded by the glass. The glass is thereafter comminuted into a granulate consisting of a plurality of small glass bodies. The granulate is reheated so that pigment particles exposed by the comminuting are resurrounded by the resoftened glass. The glass pigment mixture can alternatively be suspended in a liquid and poured into a mold before heating in order to form glass bodies having a particular shape.

Abstract: A process for producing a rod glass having a refractive index distribution, which includes pressing a glass at a temperature below the glass transition temperature to form a glass having a density increased towards the surface layer thereof, or alternatively includes heating a glass at a temperature around the transition temperature at the lowest to prepare glass having a uniformly enhanced density and heating the treated glass under a pressure lower than the applied pressure at a temperature below the glass transition temperature of the glass to prepare a glass having a density increased towards the central portion.

Abstract: Methods of making gradient property refractive elements such as gradient index lens blanks. The spatial distributions of constituents achieved by subjecting various starting assemblages to various diffusion conditions are predicted. Each such predicted spatial distribution of constituents is converted to a spatial distribution of the graded property. The property distribution which best approximates a desired distribution is selected, to thereby select one starting assemblage and one set of diffusion conditions. That assemblage and set of conditions are used in fabrication of the element.

Abstract: A method of manufacturing distributed index optical elements is disclosed. The method comprises a step of preparing silica sol including at least one of metal dopants, a step of dipping, after subjecting the silica sol to a gelling treatment, the silica gel in an elute into which a part of metal constituents other than silicon including in the gel is selectively eluted, and a step of drying and sintering the silica gel.

Abstract: A sol-gel process for forming a germania-doped silica glass rod that is suitable for use as a preform in the manufacture of high numerical aperture optical fibers. The sol is produced by mixing together prescribed quantities of alkoxides including tetraethyl orthosilicate and tetraethyl orthogermanate, deionized water, ethanol and a precipitation catalyst such as hydrofluoric acid. Premature precipitation of germania is avoided by adding ethanol and deionized water to an alkoxide solution at a controlled, drop-wise rate and by then similarly adding the catalyst at a controlled, drop-wise rate. After drying the resulting gel, sintering is performed by chlorinating the dry gel to remove residual hydroxyl groups, then oxygenating the chlorinated gel to remove the chlorine, and finally heating the oxygenated gel in helium to a temperature of about 1300.degree. C. Chlorinating and oxygenating the gel for extended time durations, and maintaining the gel above 1200.degree. C.

Abstract: A moil crack-off system for a funnel is provided, wherein a pick-up apparatus is arranged intersectionally above a conveyor that is extended from the shaping process of the funnel, and a pair of ware transfers are arranged in parallel on either side of the conveyor. The funnel that is riding on the conveyor is absorbed at a predetermined position by vacuum pads that are loaded on the carriers of the pick-up apparatus, and is moved in a three-dimensional manner to either of the ware transfers. The ware transfers deliver the three-dimensionally moved funnel to a scoring part and a two-step fire polishing part, which are arranged within the ware transfers, so that the moil of the funnel is cracked off automatically.

Abstract: Relatively large bodies of low-alkali silicate and other glass can be prepared conveniently by a particulate sol-gel process. The glass comprises at least 85 mole % SiO.sub.2, 1-12 mole % oxide of one or more of Li, Na, K, Rb, Cs, Ti and Zr, 0-6 mole % of oxide of Al, and optionally at most 2.5 mole % of oxide of elements other than Si, Li, Na, K, Rb, Cs, Ti, Zr and Al. The process comprises forming particles from a first sol that comprises Si and one or more of Li, Na, K, Rb, Cs, Ti and Zr, and optionally additionally comprises Al. The process further comprises forming a second sol by dispersing the particles in an aqueous liquid, gelling the second sol, and heat treating the resulting gel body such that the glass results.

Abstract: The method of manufacturing a silica glass preform comprises the steps of inserting a rod-like member mainly containing a ductile material, into a forming space of a mold, charging the remaining space of the forming space with a forming material containing silica glass powder or doped silica glass powder, compressing the mold charged with the forming material from outside such as to form a porous glass body of the forming material around the rod-like member, removing the rod-like member from the porous glass body, inserting a glass rod into the hole formed after removal of the rod-like member, purifying said porous glass body in which the glass rod is inserted, and consolidating said porous glass body purified in the above purifying step.

Abstract: A method of manufacturing a gradient index optical element comprises preparing a sol using silicon alkoxide and an aqueous metal salt solution as a source of index-modifying cations. The sol is treated to obtain a wet gel. Metal salt from the wet gel is eluted by immersing the wet gel in a solvent to produce a concentration gradiation of the metal salt in the wet gel. The metal salt is fixed in the wet gel by immersing the wet gel in a solvent. The steps of eluting and fixing are repeated so that a gradient index optical element is produced having a large difference in refractive index between the outer periphery portion and the center of the gel.