Gurit Ampro Collodial Silica is an agent used to control the thixotropy ‘Sag’ characteristics of a resin system. Adding the powder in varying amounts to the resin mix containing other types of filler, the handling and flow characteristics can be controlled. Adding small quantities to the resin mix already containing glass bubbles and microballoons will give non sag properties and easier handling. Collodial Silica is recommended to be added in small quantities, due to it’s hardening properties. Increased quantities added to a mixture hardens the product making it difficult to sand.