56 BULLETIN 801, U. S. DEPARTMENT OF AGRICULTURE. 
should be done before the tin is applied, or preferably before the 
lumber is nailed together. 
In addition to the preventive methods and care described, pre- 
servative treatment should be used when trying conditions of 
humidity or poor ventilation have to be met. Discussion in some 
detail of such treatment is contained in various bulletins prepared 
by the Forest Service. 2 
Checking decay already in progress in a building is done best by 
removing permanently all timbers affected noticeably and then sub- 
jecting the building to the process of heating and ventilating previ- 
ously described. Constant ventilation of the ends of timbers should 
be assured. 
In addition to the strictly preservative treatment described, the 
application of oil paint to exposed woodwork is valuable. However, 
no effort should be made to paint wood already treated with creosote, 
as paint will not adhere to such surfaces. No paint or other surface 
applications should be made until lumber is dry and heavy timbers 
should not be painted for a year after cutting. Paint applied to par- 
tially green lumber serves to retain the moisture and is conducive to 
rapid decay. 
Fire-retardant treatment for wood has not been developed on a 
commercial scale applicable to ih.Q warehouse. The only practical 
methods of increasing the resistance to fire offered by this wood con- 
struction is a surface application of whitewash or a water paint of 
similar character, or a few other paints carrying chemicals of fire- 
retardant properties. The most effective of these are limited to 
interior use. No such treatment can be relied upon to retard the 
spread of a hot fire. 3 
Information on the subject of yard piling and seasoning of lumber is con- 
tained in Bulletin No. 552 of the U. S. Department of Agriculture: The 
Seasoning of Wood, 1917. 
A very fine discussion on Dry Rot in Factory Timbers is issued by the In- 
spection Department, Associated Factory Mutual Fire Insurance Companies, 31 
Milk Street, Boston. 
2 See U. S. Department of Agriculture Bulletins No. 101 : Relative Resistance 
of Various Conifers to Injection with Creosote ; No. 606 : Relative Resistance of 
Various Hardwoods to Injection with Creosote ; No. 145 : Tests of Wood Pre- 
servatives ; No. 286 : Strength Tests of Structural Timbers Treated by Commer- 
cial Wood-Preserving Processes. 
3 Below is a satisfactory formula for whitewash for interior use. For exterior 
use the glue and rice should be omitted and it should be remembered that no 
whitewash is really satisfactory when exposed to weather. 
Slake one-half bushel of unslaked lime with boiling water, keeping it covered 
during the process; strain it and add a peck of salt dissolved in warm water; 
8 pounds of ground rice, put in boiling water and boiled to a thin paste ; one- 
half pound powdered Spanish whiting and a pound of clear glue dissolved in hot 
water; mix these well together and let the mixture stand for several days. 
Keep the wash thus prepared in a kettle or portable furnace, and when used 
put it on as hot as possible with painter's or whitewash brushes. 
