AMPRO™ Colloidal Silica is an agent which is used to control the thixotropy or ‘sag’ characteristics of a resin system. By adding colloidal silica powder in varying amounts to a resin mix containing the other filler types mentioned, the handling and flow characteristics can be controlled. Relatively small quantities added to a resin mix containing glass bubbles or microballoons will give non-sag properties and impart easier handling. Colloidal silica is also used with microfibres to produce a mix suitable for use as a high strength, non-sagging structural adhesive, particularly for non-absorbent materials such as grp. The inclusion of colloidal silica has the effect of increasing the hardness of the resulting mix which will create more difficulty when sanding. For this reason colloidal silica is usually added in the minimum quantities to any mix for which sanding is anticipated. In some applications this feature can be used to an advantage, for example to create a hard wearing edge or surface.