Limewash - Application - Patchy Limewash

Patchy Limewash can be caused by:

1. A wet edge not being worked. Each elevation must be finished in full or if this is not possible then breaks in work should be hidden behind downpipes or natural breaks in the render. 
2. Differential drying. Often caused by the differing porosity of backgrounds. The final shade that a limewash dries is influenced by the speed in which it dries. The quicker a limewash dries and carbonates, the lighter the final shade will be. 

Resolution

Limewash will always have a slightly variegated finish and will naturally dry slightly different colours when applied to different backgrounds. The final colour of the limewash will be determined by the rate at which it dries and carbonates, the quicker it dries and carbonates the lighter it will be. So limewash applied to backgrounds of differing porosities will naturally dry different colours Repeated applications of limewash may not get rid of patchiness, and the resultant finish may have the same patchiness as the previous coat. We call this telegraphing. If the patchiness is unsightly it may mean that the limewash needs to be removed with a jet wash and reapplied in accordance with manufacturers guidelines.

If it is thought that patchiness is likely to be caused be differing porosities of background then a shelter coat could be applied. Shelter coats are essentially a thin coat of a brush applied render; this will help to even up suction in the background.