Viscosity...Viscosity tells you how thick or thin a liquid is. The higher the viscosity number the thicker the liquid. Durometer... refers to hardnerss ... How hard or how soft material is. Shore 'D' durometer refers to hard materials and surfaces such as the rigid resins. Softer materials are rated on the Shore 'A' scale. The higher the number, the harder it is. How easy it is to flex a rubber or the flexible urethanes is decided by both the hardness and the thickness as soft flexible materials feel harder as the part thickness increases. Tensile Strength...is measured by grabbing two ends and pulling them apart until the part breaks. This measures the tensile strength and also gives you an idea of how elongation by measuring how much it stretches before breaking as well. Pot Life...Amount of time you have after two components have been mixed together before your chemical reaction starts to occur and your compounds will begin to set. Demold Time...The time you have to wait after it is solid enough to remove from your mold box or piece from your mold. At the de-mold time, it is solidified enough to handle but has not reached a full homogenous cure or it's full strength. Cure Time...Your materials have reached "full strength and cure" Fillers... Materials used to manipulate the resin to achieve a specific look, appearance, or function. There are many materials that act as fillers such as sand, aluminum powder, granite, calcium carbonate, micro-balloons, porcelain powders, etc. The percentage of filler recommended depends on the purpose and requirements of the finished piece. Typically 50-100% by volume is added to achieve the desired effect and not thicken the material so much that you are unable to mix and pour the material effectively.