The Gambier Parry process is a development of the classical technique of fresco for painting murals, named for Thomas Gambier Parry. True fresco is the technique of painting on fresh lime plaster whereby the pigments are fixed by the carbonatation of the lime (calcium hydroxide). The technique requires no other binding medium and the fixing process produces a durable crystalline paint layer. However, only a limited range of pigments are suitable for true frescoes and the technique requires careful application under controlled conditions, and relatively low humidity thereafter. In some environments, conventional fresco colours can rapidly accumulate dirt and grime. The decoration of the new Houses of Parliament in the mid-nineteenth century saw an embarrassing failure of true fresco in Engl