Table 1 . - -Classification of retardants by effective life and thickening agents 



Retardant ' 



Effective life 



Short-term 



Long-term 



Thickening agent 



Clay 



Gum 



Gelgard 

 Algin-gel 

 Bentonite 

 Phos-Chek 202 

 Fire-Trol 



X 

 X 

 X 



X 

 X 



X 



X 



X 

 X 



NOTE: Table 7, p. 28, shows composition, mixing quantities , and method of mixing. 



"""Mention of trade or brand names is solely for convenience in identification. Such 

 mention does not imply endorsement by the U.S. Forest Service of the products men- 

 tioned, nor does it imply nonendorsement of unnamed products. 



All five retardants and water were used in the drying test. Water, however, penetrated 

 through the fuel instead of adhering to it, and formed puddles on the bottom of the drying pans. 

 This caused spurious drying rates; hence we eliminated water from further consideration in 

 the present study. 



We used only one short-term and one long-term retardant in the burning test on the 

 assumptions that: 



1. Short-term retardants have similar fire -inhibiting characteristics. 



2. Long-term retardants, as now manufactured, have similar fire -inhibiting char- 

 acteristics. 



3. The fire -inhibiting characteristics of long-term retardants as a group are significantly 

 different from those of short-term retardants. 



Fuel 



We used ponderosa pine needles for fuel bed material in all tests because of their natural 

 organic composition and also because pine-needle beds can be reproduced with reasonable 

 accuracy; also, pine needles are readily available. Earlier research analyzed the burning of 

 untreated ponderosa pine fuel beds under a wjde range of fuel and air moisture content and en- 

 vironmental conditions; the results were the basis for comparison of the burning phenomena of 

 treated and untreated fuels. 3 



Needles from the current year's cast were cleaned, mixed, and stored in bins. At least 

 2 weeks prior to use the needles were place in 10-pound-capacity wire baskets on open shelves 

 in the fuel preparation room, where the ambient environmental conditions caused the moisture 



"Schuette, Robert D. Preparing reproducible pine needle fuel beds. U.S. Forest Serv. 

 Research Note INT-36, 7 pp., illus. 1965. 



Rothermel, R. C, and Hal E. Anderson. Fire spread characteristics determined in 

 the laboratory. (In preparation.) 



3 



