TNT is prone to exudation of dinitrotoluenes and other isomers of trinitrotoluene. Even small quantities of such impurities can cause such effect. The effect shows especially in projectiles containing TNT and stored at higher temperatures, e.g. during summer. Exudation of impurities leads to formation of pores and cracks (which in turn cause increased shock sensitivity). Migration of the exudated liquid into the fuze screw thread can form "fire channels", increasing the risk of accidental detonations; fuze malfunction can result from the liquids migrating into its mechanism. Calcium silicate is mixed with TNT to mitigate the tendency towards exudation.