Step 5 — Coat the interior of the Airform with Shotcrete, over the Monoform Primer and to a thickness of at least 1/8 inch — up to 1/4 inch (preferably 1/4 inch). This is Monolithic’s standard mix with Kel-Crete and nylon fibers. Apply the second coat of concrete as soon as the first coat is ready or the next day (another 1/4" to 1/2" is about right). Concrete is ready for its second layer when it feels tough — not necessarily brittle. The time to recoat in hot weather can be in 1 hour. In colder conditions it may require heat and curing overnight.