34 FUMIGATION METHODS 
cloth, filling the fiber in the same way, making it 
when dried thoroughly gas-proof. As soon as the 
paint is dry the sheet is covered with another coat of 
rather flexible paint. When dry this coating makes a 
perfectly tight tent, with a smooth surface and quite 
as flexible and easily handled as the oiled tent. 
Still another method is used in some places. A 
decoction is made by filling a barrel two-thirds full of 
chopped stems and leaves of the common prickly pear 
cactus (Opuntia engelmant). Afterward the barrel is 
filled with cold water and is allowed to stand twenty- 
fourhours. ‘The liquid is then drawn off and ready for 
use by adding a pigment, like yellow ochre or Venitian 
red. Sometimes a small quantity of glue is added. 
To prevent molding when not in use and folded, a small 
quantity of tannin solution is added to the mixture. 
This solution can be applied to the tents with a brush, 
but where a sufficient quantity is on hand it is better 
to soak the sheets over night in a vessel containing the 
mixture. They should then be taken out of the 
material, thoroughly drained, and spread out to dry. 
This method, however, is not generally used, but has 
given very satisfactory results, as the cloth is not 
stiffened, and is made quite flexible and easily handled. 
