The following is a short description of a prior study conducted by McNitt and Landschoot (2004). For a copy of the complete study click the reference below.

The objective of this study was to evaluate the surface hardness of varying configurations of an infilled synthetic turf system called SofSport™ under wet and dry conditions. Specifically, we wanted to 1) determine the effect of underlying pad thickness and type, infill media depth, sand sizes, and sand to crumb rubber ratio, on surface hardness as measured by the F355 method and the CIST and 2) compare the F355 method with the CIST to determine if one method is preferred when testing synthetic infill systems. Surface hardness differences between pad thickness and types were small but all pad treatments had lower surface hardness values compared to the no-pad treatments. Infill media depth did not affect surface hardness under dry conditions. Under wet conditions, the 38 mm infill media depth resulted in lower surface hardness than the 25 mm depth. The mixing of sand and crumb rubber infill media resulted in lower surface hardness values than sand or crumb rubber alone. When mixed with crumb rubber, finer sands measured higher in surface hardness than coarser sands. Under the conditions of this study the relationship between the Gmax values generated by the F355 method can be compared to the values generated by the Clegg Impact Soil Tester using the regression equation F355 × 0.66 − 9.3 = Clegg Impact Soil Tester. The regression coefficient for this equation was 0.95 and indicates that the Clegg Impact Soil Tester would be a suitable device to measure the surface hardness of SofSport installations.