Graphenstone Siena - How to create a Limewash effect Siena is a natural lime-based paint specifically formulated to create limewash effects in interior and exterior surfaces. Enjoy the timeless beauty of slaked-lime matte finish with an easy application. Siena contributes to create healthy spaces thanks to its unique formula, that absorbs CO2 during the carbonatation process and is free of preservatives and toxic substances. Highly breathable. With Graphenstone technology for enhanced performance, flexibility and durability.