484 INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



mended by K. S. Woglum, but the material, though allowing but a small 

 escape of gas, was not able to stand the rough usage. After several 

 years of trial it is becoming the almost unanimous opinion of fumigators 



Fig. 483. — Marked fumigating tent over tree. (After Pierce, P. C. Jr. Ent.) 



that by far the best of all tent material is a selected 8-ounce army duck. 

 Though somewhat coarse and open, it is able to hold the gas well and 

 may be used almost twice as long as the drills. 



Tents should be ordered a little larger to allow for shrinkage 

 when dipped. 



Dipping. — To prevent moulding and rotting, new tents are some- 

 times treated in a tannin bath. A suitable outfit for this work is 

 shown in Fig. 484. 



The tank should have a capacity of from two hundred and fifty to 

 three hundred gallons. Oakbark extract of tannin is used at the rate 

 of one pound to every five gallons of water. Six or eight pounds of 

 tannin and the amount of water removed with the tent should be 

 added after each is dipped. 



The tannin solution should be brought to a boil and the tents im- 

 mersed for half an hour, after which they are removed and spread 

 out to dry. 



A 45-foot tent will shrink about one foot all around in dipping 

 (allowing for some stretching by use afterward). 



The cost of dipping for tannin, fuel, labor, etc., amounts to about 

 $1.20 to $1.50 outside of equipment. 



