412 ARCHITECTURAL SCIENCE TEACHING. 



"harmony of colors" they must be equalized to the varying proportions 

 shown in the solar spectrum — the three primaries being used either in their 

 purity or compounded. The eye being constructed to see white light, when 

 looking on a colored surface, it is best pleased by a contrast. Contrasting 

 colors to harmonize should be mutual complementaries of each other — mak- 

 ing up the full complement of colors contained in the solar rays. The com- 

 ptlement of any primaiy — say, red — wnll be the secondary comjDounded from 

 the other two primaries — as green from blue and yellow — red will thus 

 harmonize with green, blue with orange and yellow with violet. The best 

 proportion for mixing primaries, so as to harmonize, is : red, 5 ; blue, 8 ; 

 and yellow, 3. The latter is the most vivid, and should obtain a prominent 

 position. Blue is least vivid and retiring, and should be kept in the back- 

 ground — red to be used as an intermediate color. 



Question. — Describe the jjroper ynode of jyainting wall surfaces. — To paint 

 wall surfaces properly often five coats are necessary; but if the plaster be 

 not vei-y absorbent four will be sufficient. If the work is required without 

 gloss the last coat is mixed with turpentine only, which is called flatting; 

 if the work be not flatted the finishing coat is two of turpentine to one of oil. 

 For the priming coat boiled oil should be used, then the three coats of white 

 lead and oil, or more if required; generally the first coats should be some 

 shades darker than the finishing coat. The proper drier to be used for walls 

 is sugar of lead, and in painting wall surfaces great care should be used in 

 selecting the very best quality of oils and white lead — the older the oil the 

 better. 



Question. — What is the best j^aint for ironicork? — The best paint for iron- 

 work is either the oxide of iron paint, known as the Torbay i^aint, or the 

 silicate oxide paint, both consisting of oxide of iron and silicious matter, to 

 which any color may be added and aj)2)lied in the usual way. They can bo 

 applied even after the surface has commenced to rust, as from their nature 

 they amalgamate freely with the rust, forming an imj^ervious coating adher- 

 ing well to the surface, and yet sufficiently elastic to prevent cracking when 

 the iron expands or contracts under variations of temperature. Bituminous 

 or tar mixtures, thinned with linseed oil, are w^ell adapted for ironwork, 

 especially when they can be applied hot, or to the heated surface of the 

 metal, so as to insure a firm adhesion by entering the pores. A mixture of 

 silicate oxide with tar also forms a good durable coating on iron. When 

 ironwork is to be painted with ordinary lead paint red lead should be used. 

 The adhesion of such a coating on ironwork can seldom be depended on in 

 consequence of the non-poraus surface. This is further prevented by the 

 galvanic action that sets in between the iron and lead. Galvanizing, or 

 coating the surface with a preparation of zinc, is also frequently resorted 

 to as a i^reservative. With all such coatings the surface must be perfectly 

 clean and free from rust. It is advisable, so as to prevent rusting, that all 

 ironwork should be coated with some preservative soon after it leaves the 

 mould, forge or mill. — Building Neics. 



