transparent coating when spread in a thin film over a surface,  affording  protection  and  decoration. Of  the  common  types  of  varnishes,  the  most important are the oils, including spar, flat, rubbing, and color types. These are extensively used to finish and  refinish  interior  and  exterior  wood  surfaces,  such as  floors,  furniture,  and  cabinets.  Spar  varnish  is intended  for  exterior  use  in  normal  or  marine environments, although its durability is limited. To increase durability, exterior varnishes are especially formulated  to  resist  weathering. Varnishes produce a durable, elastic, and tough surface  that  normally  dries  to  a  high-gloss  finish  and does  not  easily  mar.  Often,  a  lower  gloss  may  be obtained by rubbing the surface with a very fine steel wool. However, it is simpler to use a flat varnish with the  gloss  reduced  by  adding  transparent-flatting pigments,  such  as  certain  synthetic  silicas.  These pigments are dispersed in the varnish to produce a clear finish that dries to a low gloss, but still does not obscure  the  surface  underneath  (that  is,  you  can  still see the grain of the wood). SHELLAC Shellac is purified lac formed into thin flakes and widely used as a binder in varnishes, paints, and stains. (Lac  is  a  resinous  substance  secreted  by  certain insects.)  The  vehicle  is  wood  alcohol.  The  natural color  of  shellac  is  orange,  although  it  can  be  obtained in white. Shellac is used extensively as a finishing material and a sealant. Applied over knots in wood, it prevents  bleeding. LACQUERS Lacquers may be clear or pigmented and can be lusterless,   semigloss,   or   glossy.   Lacquers   dry   or harden  quickly,  producing  a  firm  oil-  and  water- resistant film. But many coats are required to achieve adequate dry-film thickness. It generally costs more to use lacquers than most paints. STAINS Stains are obtainable in four different kinds: oil, water,  spirit,  and  chemical.  Oil  stains  have  an  oil vehicle;  mineral  spirits  can  be  added  to  increase penetration. Water stains are solutions of aniline dyes and  water.  Spirit  stains  contain  alcohol.  Chemical stains work by means of a chemical reaction when dissolved by water. The type of stain to use depends largely on the purpose, the location, and the type of wood being covered. SURFACE PREPARATION LEARNING OBJECTIVE: Upon completing this section, you should be able to describe the procedures  used  in  preparing  surfaces  for painting. The  most  essential  part  of  any  painting  job  is proper surface preparation and repair. Each type of surface requires specific cleaning procedures. Paint will not adhere well, provide the protection necessary, or have the desired appearance unless the surface is in proper  condition  for  painting.  Exterior  surface preparation is especially important because hostile environments  can  accelerate  deterioration. METALS As a Builder, you are most likely to paint three types of metals: ferrous, nonferrous, and galvanized. Improper protection of metals is likely to cause fatigue in the metal itself and may result in costly repairs or even  replacement.  Correct  surface  preparation,  prior to painting, is essential. Ferrous Cleaning ferrous metals, such as iron and steel, involves  the  removal  of  oil,  grease,  previous  coatings, and dirt. Keep in mind that once you prepare a metal surface  for  painting,  it  will  start  to  rust  immediately unless you use a primer or pretreatment to protect the surface. Nonferrous The  nonferrous  metals  are  brass,  bronze,  copper, tin, zinc, aluminum, nickel, and others not derived from   iron   ore.   Nonferrous   metals   are   generally cleaned with a solvent type of cleaner. After cleaning, you should apply a primer coat or a pretreatment. Galvanized Galvanized iron is one of the most difficult metals to prime properly. The galvanizing process forms a hard,  dense  surface  that  paint  cannot  penetrate.  Too often,  galvanized  surfaces  are  not  prepared  properly, resulting in paint failure. Three steps must be taken to develop a sound paint system. 1. Wash the galvanized surface with a solvent to remove grease, waxes, or silicones. Manufac- turers  sometimes  apply  these  to  resist  “white rust” that may form on galvanized sheets stored 8-4