Painting the Farm and City Home 



629 



lect their repainting would be wiser 

 to use white lead paint. 



CORRECT THICKNESS of coating is 

 necessary for reliable performance of 

 the paint. For linseed-oil house paints, 

 experience has shown that correct 

 thickness is about 0.005 inch. Coatings 

 much thinner than that wear away 

 sooner than is necessary ; coatings much 

 thicker than that are unduly brittle and 

 are likely to behave badly. A common 

 mistake the first time a house is painted 

 is to apply too little paint. Thereafter, 

 in maintaining the coating, the ten- 

 dency in towns and cities (although less 

 often on farms) is to paint too often or 

 with too much new paint at a time. 



For painting new woodwork it takes 

 about 3.6 gallons of prewar house 

 paints, which are rich in linseed oil, to 

 leave a coating 0.005 inch thick on 

 1,000 square feet of surface. It can be 

 done either with three coats of about 

 1.2 gallons each or, if the paint is of 

 the best quality, with two coats of 1.8 

 gallons each. Present paints, however, 

 usually contain less linseed oil and 

 more volatile thinner than the prewar 

 paints. It therefore takes about 4.5 gal- 

 lons (three coats of 1.5 gallons each) 

 to leave the desired 0.005 inch of coat- 

 ing on 1,000 square feet. Two coats 

 with such paint would require 2.25 

 gallons each, which is more paint than 

 it is practicable to apply on smooth 

 surfaces at one time. 



REPAINTING should not be done until 

 much of the coating has worn away, 

 say 0.002 inch of the original 0.005 

 inch. The repainting should then re- 

 store the lost thickness but not much 

 more. That can be done with 1.4 gal- 

 lons of prewar paint, or 1.8 gallons of 

 present paint, on 1,000 square feet of 

 surface. The repainting in such cases 

 can be done with one heavy coat or 

 two thin ones. 



The present method of selling paints 

 by trade brands without conforming to 

 trade standards of any kind makes it 

 exceedingly difficult for paint users to 

 exercise choice in selecting kinds of 



paint or to learn how they are best 

 used. The manufacturers' directions for 

 applying paint, for example, fail to in- 

 dicate the important difference in the 

 methods of applying the prewar and 

 the present paints. The user is allowed 

 to assume that he may properly spread 

 the present paints over as much surface 

 as he formerly did the prewar paints. 

 Most responsible paint manufacturers 

 report the composition of their paints 

 on the labels, as the laws of some States 

 require, but the formulas are stated in 

 a complicated, highly technical man- 

 ner. Paint users, who are able and will- 

 ing to learn how, can get the needed 

 information from the formulas by 

 calculations. Methods of making the 

 calculations are described in my book- 

 let, Classification of House and Barn 

 Paints, Technical Bulletin 804 of the 

 Department of Agriculture. The bul- 

 letin points out a method of classify- 

 ing paints by group, type, and grade 

 that, if adopted by the industry, would 

 simplify the explanation of paint to 

 paint users and permit painting pro- 

 grams for buildings to be set forth in a 

 reasonably simple manner. 



THIS CLASSIFICATION of native 

 woods for relative ability to hold paint 

 coatings may be helpful. 



Type A are paints that wear out by 

 checking and crumbling, such as pure 

 white lead paint. 



Type B are paints that wear out by 

 cracking, curling, and flaking, such as 

 paints containing zinc oxide mixed 

 with other pigments. 



Group 1 Woods on which paints of 

 types A and B last longest. 

 Softwoods: 

 Alaska-cedar. 

 Incense-cedar. 

 Northern white-cedar. 

 Port-Orford-cedar. 

 Southern cedar. 

 Western redcedar. 

 Baldcypress. 

 Redwood. 



Group 2 Woods on which paints of 

 type B wear out faster than they do on 

 woods of group 1 , through paints of type 



