to soften the light or provide privacy. It may be obtained with a pattern on one or both sides. Patterned Patterned  glass  has  the  same  composition  as window and plate glass. It is semitransparent with distinctive  geometric  or  linear  designs  on  one  or  both sides. The pattern can be impressed during the rolling process or sandblasted or etched later. Some patterns are also available as wired glass. pattern glass allows entry of light while maintaining privacy. It is also used for decorative screens and windows. Patterned glass must be installed with the smooth side to the face of the putty. Laminated Laminated glass is composed of two or more layers of either sheet or polished plate glass with one or more layers of transparent or pigmented plastic sandwiched between the layers. A vinyl plastic, such as plasticized polyvinyl  resin  butyl  0.015  to  0.025  inch  thick,  is generally  used.  Only  the  highest  quality  sheet  or polished plate glass is used in making laminated glass. When this type of glass breaks, the plastic holds the pieces of glass and prevents the sharp fragments from shattering.  When  four  or  more  layers  of  glass  are laminated with three or more layers of plastic, the product is known as bullet-resisting glass. Safety glass has only two layers of glass and one of plastic. Safety Safety glass is available with clear or pigmented plastic,  and  either  clear  or  heat-absorbing  and glare-reducing glass. Safety glass is used where strong impact may be encountered and the hazard of flying glass must be avoided. Exterior doors with a pane area greater  than  6  square  feet  and  shower  tubs  and enclosures  are  typical  applications. Glazing compounds must be compatible with the layers of laminated plastic. Some compounds cause deterioration  of  the  plastic  in  safety  glass. Mirrors Mimers  are  made  with  polished  plate,  window, sheet, and picture glass. The reflecting surface is a thin coat of metal, generally silver, gold, copper, bronze, or chromium, applied to one side of the glass. For special mirrors,  lead,  aluminum,  platinum,  rhodium,  or  other metals  may  be  used.  The  metal  film  can  be  semi- transparent  or  opaque  and  can  be  left  unprotected  or protected with a coat of shellac, varnish, paint, or metal (usually copper). Mirrors used in building construction are usually either polished plate glass or tempered plate glass. Proper installation requires that the weight of the mirror be supported at the bottom. Mastic installation is not recommended because it may cause silver spoilage. Plexiglas® Sheets  made  of  thermoplastic  acrylic  resin (Plexiglas®and  Luciteo,  both trade names) are available in flat and corrugated sheets. This material is readily formed into curved shapes and, therefore, is often used in place of glass. Compared with glass, its surface is more readily scratched; hence, it should be installed in out-of-reach locations. This acrylic plastic is obtainable in transparent, translucent, or opaque sheets and in a wide  variety  of  colors. GLAZING MATERIALS In this section, we’ll discuss the various types of sealers  you’ll  need  to  install,  hold  fast,  and  seal  a window  in  its  setting. Wood-Sash Putty Wood-sash  putty  is  a  cement  composed  of  fine powdered chalk (whiting) or lead oxide (white lead) mixed with boiled or raw linseed oil. Putty may contain other drying oils, such as soybean or perilla. As the oil oxides, the putty hardens. Litharge (an oxide of lead) or special  driers  may  be  added  if  rapid  hardening  is required. Putty is used in glazing to set sheets of glass into frames. Special putty mixtures are available for interior and exterior glazing of aluminum and steel window sash. A good grade of wood-sash putty resists sticking to the putty knife or glazier’s hands, yet it should not be too dry to apply to the sash. In wood sash, apply a suitable primer, such as priming paints or boiled linseed oil. Putty  should  not  be  painted  until  it  has  thoroughly set. Painting forms an airtight film, which slows the drying. This may cause the surface of the paint to crack All  putty  should  be  painted  for  proper  protection. Metal-Sash  Putty Metal-sash putty differs from wood putty in that it is formulated to adhere to nonporous surfaces. It is used 4-21