AIRTIGHT premium quality, fibre reinforced polymer paste which is applied quickly and easily by brush. Forms an airtight and vapour tight elastic membrane after drying. Works on almost all mineral surfaces. Fills cracks of up to 2mm due to the fibre content. Changes colour after drying from blue to black. Once dry a second coat (or more) can be applied if required. Can also be painted or plastered over once dry. Virtually odourless.