Abstract: This invention is related to glasses particularly useful in the fabrication of multifocal lenses for ophthalmic applications. The inventive glasses exhibit a refractive index between 1.599-1.602, an Abbe number between 40.5-41.5, a density between 2.64-2.66 g/cm.sup.3, a transmission of visible radiation at 400 nm through a thickness of 10 mm greater than 83%, a softening point between 670.degree.-680.degree. C., a birefringence upon sealing, measured as described, between -150 and +150 nm/cm, and consist essentially, expressed in terms of weight percent on the oxide basis, of:______________________________________ SiO.sub.2 52-57 K.sub.2 O 11.0-16.0 B.sub.2 O.sub.3 2.5-7.0 CaO 2-3.5 Al.sub.2 O.sub.3 0-1 ZrO.sub.2 1-1.5 Li.sub.2 O 0.3-0.8 TiO.sub.2 15.0-16.2 Na.sub.2 O 5.4-8.2 As.sub.2 O.sub.3 0.1-0.

Abstract: This invention relates to the preparation of glass-ceramic articles in which potassium fluorrichterite and/or a related fluormica constitutes the predominant crystal phase(s). The precursor glasses can be crystallized in situ very rapidly and exhibit very little thermal deformation during the crystallization heat treatment. The base glasses are essentially free of Li.sub.2 O and consist essentially, expressed in terms of weight percent on the oxide basis, of:______________________________________ SiO.sub.2 61-70 Na.sub.2 O 0.5-3 BaO 0-3.5 Al.sub.2 O.sub.3 2.75-7 K.sub.2 O 2.5-5.5 P.sub.2 O.sub.5 0-2.5 MgO 11-16 Na.sub.2 O + K.sub.2 O <6.8 CaO 4.75-9 F 2-3.

Abstract: This invention is directed to transparent photochromic glasses that can darken to a comfort range, i.e., between about 35-60%, or to a dark range, i.e., below 35%, depending upon glass composition, and will exhibit a faded transmittance after five minutes' removal from actinic radiation higher than 70%. The base compositions of the glasses consist essentially, in weight percent, of about______________________________________ SiO.sub.2 46-60 MgO 0-3.5 B.sub.2 O.sub.3 16-28 CaO 0-6 Al.sub.2 O.sub.3 4-11 SrO 0-6 ZrO.sub.2 2-6 BaO 0-6 Al.sub.2 O.sub.3 + ZrO.sub.2 6-13 MgO + CaO + SrO + BaO 0-7 Li.sub.2 O 2-5 P.sub.2 O.sub.5 0-5 Na.sub.2 O 0-4 TiO.sub.2 0-3 K.sub.2 O 2.5-9 ______________________________________For a comfort glass the photochromic elements consist essentially, as analyzed, of ______________________________________ Ag 0.13-0.18 Br 0.08-0.14 Cl 0.16-0.34 CuO 0.001-0.

Abstract: This invention relates to the production of opal glasses having a creamy-white tint which are suitable for forming culinary articles. The opacity is obtained through precipitation of fluorides, preferably NaF. The creamy-white tint results from the association of Fe.sub.2 O.sub.3 with TiO.sub.2 and/or As.sub.2 O.sub.3 and/or CeO.sub.2, with the addition of nitrates. The preferred composition of the final glass consists essentially, in weight percent, of:______________________________________ SiO.sub.2 70-73 Fe.sub.2 O.sub.3 0.1-0.25 Na.sub.2 O 10.5-13 TiO.sub.2 0.1-0.7 Fluorine 4-5.5 As.sub.2 O.sub.3 0.05-0.4 Al.sub.2 O.sub.3 6-9 CeO.sub.2 0-0.2 CaO 0.2-1.7 B.sub.2 O.sub.3 0.5-3 BaO 1-3 ______________________________________The starting composition contains NaNO.sub.3 in a proportion of 0.2-2 by weight, counted as Na.sub.2 O with regard to the glass, or an equivalent quantity of another alkali metal or alkaline earth metal nitrate.

Abstract: This invention relates to the production of sodium fluoride opal glasses tinted in a shade lying in the range from "cream-like" to "beige" by an iron-sulfur system, the analyzed quantities of sulfur (S), sulfide ions (S.sup.-2), iron (Fe), and ferric ions (Fe.sup.+3) conforming to the following expressions:S.sup.-2 /S.gtoreq.0.1570.ltoreq.Fe.ltoreq.300 ppm0.05.ltoreq.Fe.sup.+3 /Fe.sup.+2 .ltoreq.1and 3.ltoreq.S.sup.-2 .ltoreq.160 ppm when the ZnO content is below 0.1%. The glasses are especially applicable for use in culinary ware.

Abstract: This invention is concerned with the preparation of thermally crystallizable enamels suitable for application to glass-ceramics, particularly glass-ceramics having coefficients of thermal expansion less than 15.times.10.sup.-7 /.degree.C. The enamels are capable of being fired to maturity simultaneously with the precursor glass body being crystallized to a glass-ceramic. The enamels consist essentially, expressed in weight percent on the oxide basis, of:SiO.sub.2 : 36-58Al.sub.2 O.sub.3 : 8.5-16CaO: 0.5-10PbO: 27-40K.sub.2 O: 0.

Abstract: The instant invention is directed to optical glass compositions capable of being shaped under the combined action of temperature and pressure in a mold so as to obtain articles having surfaces exhibiting highly precise reproduction of the mold walls. The inventive glasses demonstrate softening points not exceeding 500.degree. C., refractive indices between about 1.65-1.82, Abbe number between about 27-39, and consist essentially, in weight percent, of______________________________________ SiO.sub.2 8-20 B.sub.2 O.sub.3 5-20 PbO 50-70 Al.sub.2 O.sub.