It reduces absorption and provides a key for subsequent finishing coats. Tikkurila Optiva 5 or. Tikkurila Optiva 3 durable top coats for a fully breathable system. For the avoidance of doubt: Tikkurila sizing 1 Litre = 0.9 Litre tin size, 3 Litres = 2.7 Litres tin size, 10 Litres = 9 Litre tin size.
