Wash powderless gloves prior to beginning the preparation; this will prevent powder from passing from gloves to teeth. Any tooth surface (Figure 6) touched or retraction cord handled while wearing gloves will be contaminated and distort the impression material in that area (Figure 7). The amount of catalyst available for the setting reaction is very small and is measured in parts per million4 and, in these amounts, can be easily inactivated. Stone dies made from hydrophobic PVS materials are harder than those obtained from polyether and hydrophilic PVS impression materials.5 In spite of their limitations, new low viscosity hydrophilic PVS impression materials have better clinical success than hydrophobic PVS impression materials. - See more at: https://www.dentalaegis.com/id/2005/10/impression-material-basics#sthash.4jHKrxDs.dpuf