Savage, N., 1958. THE RELATION BETWEEN CRITICAL SHEAR STRESS AND "25 PERCENT DRAINAGE TIME" OF AIR-FOAM. Fire Research Notes 344
In this report it is shown that a relation exists between "25 per cent drainage time" and critical shear stress. This relation differs for different foam compounds and for different batches of the same compound, but for any one batch it is shown to be independent of expansion and compound concentration.