Kerasil mastic is supplied wet in mastic tubes, ready to use. It has a soft consistency and is almost fluid. It coats very well and easily to all surfaces, and sets very hard and strong. It sets rigid and permanent, and should therefore be used with discretion in moving structures. It can be injected deep into cracks and joints, without being sucked dry by the surrounding material.
As a brick mortar the soft consistency allows thin joints to be made. As a fibre module cement it gives a considerably larger contact area than normal mortars. Exposed surfaces normally become smooth and exhibit no cracking. A thin dry film develops rapidly on the exposed surface, so bonding should be performed quickly.
Kerasil mastic is 90% pure silica and can be used up to 1300°C. It is light brown when wet, and becomes almost white when fired.
Packaging is in mastic tubes, with a nozzle. The nozzle must be rmoved and the tip cut off. Then the tube is placed in a hardware store gun (as used for silicone sealants) and the nozzle replaced. Cut the nozzle for the appropriate size to insert in the crack or flange, and squirt it in.
Wash hands well after contact and apply a moisturising cream.
Setting is slow at ambient temperature and rapid at high temperature.