BUILDING MATERIALS 171 



no surplus acid be left on the surface. It would be difficult 

 to apply any finish over the acid-stained wood if there still 

 remained any free acid. 



Varnishes. Varnishes are classed as spirit and as oil 

 varnishes. The spirit varnish is also known as shellac. It 

 is a lacquer made by dissolving in alcohol the shell or scale 

 of a family of insects which live on the bark of certain trees. 

 This shell is brownish in color and very resinous. When 

 dissolved in its native state, it is known as brown or orange 

 shellac ; when bleached , it is white shellac. It gives a very hard 

 and brittle finish. Its chief use is to seal the pores of open- 

 grained woods, where it is desired to finish a natural color 

 or with but a slight stain. It dries rapidly and is a little 

 difficult to apply without leaving laps which show after 

 the work is finished. The oil varnish is made by dissolving 

 in linseed oil some of the resinous gums such as copal, amber, 

 and anime. The copal is the cheapest and by far the most 

 extensively used. The best varnishes are slow in drying. 

 Soft gums, such as sanderad, make a quick-drying, but a 

 softer and less permanent varnish, which is short-lived when 

 exposed. Another class of varnish is made by dissolving 

 some of the better gums in well-aged turpentine. This 

 produces an intermediate grade of varnish. 



Wax. Wax is used for interior finishing work, especially 

 upon floors. It is known on the market as prepared wax. 

 It is in a pastelike form, and when allowed to set may be 

 polished and produce a highly satisfactory, though not so 

 permanent a finish as varnish. Wax may also be had in 

 dry form, such as is used on dance floors. 



Whitewash. The Lighthouse Board of the United States 

 Treasury Department uses the following mixture : yi bushel 

 lime slaked in boiling water. Keep covered while slaking. 

 Strain and add 1 peck of salt, dissolved in warm water, 3 

 pounds of ground rice, boiled to a thin paste, )4, pound 

 powdered Spanish whiting, and a pound of clear glue, dis- 

 solved in warm water. Mix well, allow to stand for several 



