Glassware is mostly made of soda lime silicate glass, colorless and transparent containers, and the iron content in glass is generally less than 0.02%. By adding a colorant to the glass raw material, colored glass can be obtained; an opacifying agent can be added to obtain an opaque glass (see glass production). Advanced arts and crafts such as goblets, perfume bottles, fruit bowls, etc., which are used to make honing carvings, are made of potassium lead silicate glass, also known as lead crystal glass. This glass contains PbO, has a high refractive index and dispersion, grinds the face when it is exceptionally bright, has a high specific gravity, and makes a crisp sound when striking. PbO containing more than 30% of all lead crystal glass, containing PbO24 ~ 30% of the lead crystal glass, containing PbO18% or less low-lead crystal glass, in addition to BaO-containing germanocrystalline glass. Cooking utensils such as coffee makers and other products use heat-resistant borosilicate glass, which has a low coefficient of thermal expansion and strong resistance to temperature changes. Glass-ceramics have better heat resistance and resistance to temperature changes, mechanical strength, and are suitable for the manufacture of wares and utensils that are often washed in hotels.