Temperature and Color
Researchers have found that the surface temperatures of synthetic turf playing surfaces are significantly higher than natural turfgrass surfaces when exposed to sunlight. (Buskirk et al., 1971; Koon et al., 1971; and Kandelin et al. 1976). Buskirk et al. (1971) found that the surface temperatures of traditional synthetic turf were as much as 35-60 °C higher than natural turfgrass surface temperatures. Buskirk et al. (1971) placed thermocouples on the inner soles of cleated shoes and had individuals walk on the synthetic surface to determine the amount of heat transferred directly from the surface to the individual's foot. Any heat gain to the foot must be dissipated by blood flow. Buskirk et al. (1971) concluded that the heat transfer from the surface to the sole of an athlete's foot was significant enough to contribute to greater physiological stress that may result in serious heat related health problems.
Surface temperatures of infill synthetic turf systems have been reported to be as high as 93°C on a day when air temperatures were 37°C (Brakeman, 2004). Researchers at Brigham Young University measured the surface and air temperature above an infill synthetic turf system before and for a period of time after water had been applied through irrigation (Brakeman, 2004). The researchers reported that after 30 minutes of irrigation the surface temperature was lowered to that of a nearby natural turfgrass surface (29°C). However, the researchers reported that the surface temperature rose very quickly and within 5 minutes had risen to 49°C. This rapid rise in temperature could be due to the lack of through wetting of the infill media, which was found to be hydrophobic. This author personally observed this field on 19 May 2004. The infill media was very hydrophobic and water was observed to bead-up and run over the surface rather than penetrate. After a 10-minute irrigation cycle, water was observed to be moving laterally over the surface while the infill media was only wet to an average depth of 1 - 2 mm. The use of a non-ionic wetting agent may help to alleviate this problem.
Morehouse (1992) suggests that the evaporation of 1.2 L m -2 h -1 of water should be sufficient to cool a traditional synthetic surface to a level near that of a natural turfgrass surface and notes that water routinely applied to synthetic surfaces, used for women's field hockey to slow ball bounce, will dampen the surface for at least one-half game even under favorable evaporative conditions (i.e. elevated air temperature and brisk air movement). The amount of water suggested for application prior to a field hockey event is 8,000 to 10,000 L spread evenly across a 105 m x 64 m surface. In our current study, we have observed that after equal quantities of irrigation were applied to the treatment plots, the traditional synthetic turf (Astroturf) remained damp for a longer period of time than nine infill synthetic turf systems. These results indicate that the formula Morehouse (1992) suggested for water application to traditional synthetic turf may not be applicable to infill systems.
We tried to measure the temperature of the synthetic turf surfaces on clear bright days. In central Pennsylvania they are sometimes few and far between. We measured both air and surface temperature using an infrared thermometer (Scheduler Model 2 LiCor Corporation) (Fig. 27).
The temperature results are shown in Tables 19, 20A, and 20B. Some surfaces registered slightly higher in surface temperature compared to others although we found few meaningful air temperature differences three feet above the surfaces.
Table 19. Surface temperature of ten synthetic turf products in 2003.
Table 20A. Surface and air temperatures (C)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
Table 20B. Surface and air temperatures (F)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
During 2004 and in 2005 we evaluated the effect of irrigation on surface temperatures. Approximatly 0.5 inches of water was applied during irrigation. The application of water significantly lowered the surface temperatures of all synthetic surfaces (Fig. 28 and 29). The temperatures rebounded somewhat after 15 minutes and then remained relatively stable for 90 and 210 minutes, respectively. There were intermittent cumulus clouds during the rating period for these days. The effect of the passing clouds can be seen in the erratic nature of the data especially at the 2 Aug 04 rating date. For this reason, we've included data from our first rating date in 2005 (Fig. 30) that was collected on a very clear day. Air temperatures were not as high as the previous rating dates. We began collecting data on 2 Jun 05 at 11:15 am. Air temperature was 73°F with 39% relative humidity and wind speed was 4-5 mph. Data collection ended at about 3:15 pm at which time air temperature was 80°F with 33% relative humididty and wind speed at 4-5 mph. Because of the almost complete lack of cloud cover, we have more confidence in the 2005 results.
Figure 28. Surface temperatures of synthetic turf plots during and after an irrigation event on 30 June 04
Figure 29. Surface temperatures of synthetic turf plots during and after an irrigation event on 3 August 04.
Figure 30. Surface temperatures of synthetic turf plots during and after an irrigation event on 2 June 05.
Irrigation again resulted in a reduction of surface temperatures for the 195 minutes measured. At the end of the experiment the surface temperatures of the irrigated plots averaged 14 degrees lower than the non-irrigated plots. The Astroturf treatment had the highest pre-irrigation temperature and consistently measured lowest in post-irrigation temperature. This trend can be observed in the 2004 data.
Temperature of a synthetic surface will depend on numerous variables. The benefit of surface cooling through irrigation may vary depending on conditions. Irrigation systems on synthetic fields have other benefits such as reduction of wear by allowing the field manager to broom the surface when wet and wash in fabric softeners and/or wetting agents. More temperature data is being collected and this report will be updated.
In order to determine the amount of matting that is occurring, color readings of the surfaces were recorded on the no wear plots at installation and on the wear plots just prior to grooming on 8 Oct 2003 using a Model CR-310 chromameter (Minolta Co, Ltd, Ramsey, NJ) (Fig. 31). The two measurements should provide the extremes of matting and by measuring color weekly during 2004 we should be able to produce a matting index.
Color data is shown in Table 21. Color data is being collected in an attempt to develop a measure of 'matting' or how much the pile lays over after simulated traffic. We measured color of the wear and no wear plots just before and just after grooming. We had hoped that these measurements would define the spectrum of color differences due to matting. We are not satisfied that this method accurately measures the amount of matting. Currently, we are unaware of an accepted method to quantitatively evaluate matting other than visual ratings.
Table 21. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2003 by the Minolta CR-310 Chroma Meter prior to and after grooming¹
Table 22. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2004 by the Minolta CR-310 Chroma Meter prior to and after grooming¹.