In authentication of machineries and cards (artifact) that are used in social acts such as economic acts, an approach of artifact metrics corresponding to biometrics is effective. Therefore, the subject is to find out a material that satisfies requirements of artifact metrics and is, preferably, suppliable stably and also economically, to establish the production method thereof, and to apply these to an individual authentication system of artifact. Porous glass, which possesses a spinodal phase separation structure, is an individual authentication medium as artifact metrics. There is provided a production method thereof, and an individual authentication system utilizing the individual authentication medium.

A formulation usable to produce plates and shaped bodies has a base slip, quartz glass particles and multicomponent glass particles that are crystallizable or at least partly crystallized. The base slip contains water as dispersion medium with a content between 30% and 50% by weight and ultrafine SiO.sub.2 particles distributed, preferably colloidally therein, with a proportion between 50% and 70% by weight. The proportion of quartz glass particles in the formulation is in the range from 40% to 70% by weight and the proportion the multicomponent glass particles in the formulation is in the range from 5% to 37% by weight. The formulation can be used in a composite material. Firing aids can be made from the composite material.

In an exemplary embodiment, a quartz glass crucible 1 includes: a high-aluminum-content layer 14B which is made of quartz glass having a relatively high average aluminum concentration and is provided to form an outer surface 10b of the quartz glass crucible 1; and a low-aluminum-content layer 14A which is made of quartz glass having a lower average aluminum concentration than that of the high-aluminum-content layer 14B and is provided on an inner side of the high-aluminum-content layer 14B, wherein the low-aluminum-content layer 14A includes an opaque layer 11 made of quartz glass containing a large number of minute bubbles, and the high-aluminum-content layer 14B is made of transparent or translucent quartz glass having a lower bubble content than that of the opaque layer 11. The quartz glass crucible is capable of withstanding a single crystal pull-up step undertaken for a very long period of time.

A method for loading a blank composed of fused silica with hydrogen, including loading the blank at a first temperature (T.sub.1) and a first hydrogen partial pressure (p.sub.1), and further loading the blank at a second temperature (T.sub.2) which is different from the first temperature and at a second hydrogen partial pressure (p.sub.2) which is different from the first hydrogen partial pressure. The first and second temperatures (T.sub.1, T.sub.2) are lower than a limit temperature (T.sub.L) at which a thermal formation of silane in the fused silica of the blank commences. Also disclosed are a lens element produced from such a blank and a projection lens that includes at least one such lens element.

A method for loading a blank composed of fused silica with hydrogen, including loading the blank at a first temperature (T.sub.1) and a first hydrogen partial pressure (p.sub.1), and further loading the blank at a second temperature (T.sub.2) which is different from the first temperature and at a second hydrogen partial pressure (p.sub.2) which is different from the first hydrogen partial pressure. The first and second temperatures (T.sub.1, T.sub.2) are lower than a limit temperature (T.sub.L) at which a thermal formation of silane in the fused silica of the blank commences. Also disclosed are a lens element produced from such a blank and a projection lens that includes at least one such lens element.

A method for producing a round tube from a ceramic material or a glass-ceramic material or mixtures thereof is described. The method comprises introducing a silicate-ceramic, oxide-ceramic and/or non-oxide-ceramic material-forming agent into a melting vessel, which has along a longitudinal axis a tubular wall which defines a tubular cavity, wherein the melting vessel rotates about its longitudinal axis. A uniform layer of the ceramic and/or glass-ceramic material-forming agents is thereby formed, lying on the inner side of the wall, by means of centrifugal forces generated by rotation and is heated by means of a heat source arranged in the inner cavity of the melting vessel until at least the inner side of the layer of material-forming agents has melted. Such tubes can be used for various industrial purposes.

Components of an electronic device, such as glass components, are susceptible to surface damage. Glass components can be strengthened by providing ceramic particles at the exposed surface of the glass. Ceramic particles can also provide optical features, such as color, opacity, and haze to enhance the appearance of the resulting composite article. Where ceramic particles are provided at the exposed surface, the ceramic particles can also produce a desired tactile feature. These features can be provided in various combinations and in different ways across different regions to produce a desired look and feel of the resulting composite article.

Components of an electronic device, such as glass components, are susceptible to surface damage. Glass components can be strengthened by providing ceramic particles at the exposed surface of the glass. Ceramic particles can also provide optical features, such as color, opacity, and haze to enhance the appearance of the resulting composite article. Where ceramic particles are provided at the exposed surface, the ceramic particles can also produce a desired tactile feature. These features can be provided in various combinations and in different ways across different regions to produce a desired look and feel of the resulting composite article.

A method for producing foam glass with high open pore content using recycled waste glass. The size of the pores of the foam glass is small and uniform, and such foam glass is suitable for building material with thermal insulating and sound proofing properties. The foam glass produced by this method is lightweight, durable and has high compression strength.

A method for producing foam glass with high open pore content using recycled waste glass. The size of the pores of the foam glass is small and uniform, and such foam glass is suitable for building material with thermal insulating and sound proofing properties. The foam glass produced by this method is lightweight, durable and has high compression strength.