Substrate Effects on the Clotting time of Human Blood

This study shows that the time required for human blood to clot varies between individuals and with the substrate upon which the blood is deposited. Human blood was collected from different individuals. Ten milliliters of each individual's blood was deposited on each of several different substrates. The times required for each person's blood to clot were compared for each of the different substrates and to the times required for each person's blood to clot in a blood tube. It was observed that if an individual's clotting time was slow or fast for one substrate, it was generally slow or fast, respectively, for other substrates. Studies were also conducted using larger blood volumes. Three individuals donated 75 mL, 105 mL, and 150 mL of blood, respectively. Each of the three blood volumes was deposited on a painted concrete floor. Clotting times for the three blood samples were recorded. Each blood sample was also monitored for changes in physical characteristics prior to, during, and following the blood clotting.