Resene Limelock is a preparatory coating designed to cure and seal cementitious substrates. It promotes curing by producing a water barrier which, unlike traditional curing membranes, can be overcoated with acrylics at any stage. This means that it can be used at the pre-cladding stage on a new build, as its ability to cure and seal the substrate means users don’t have to leave the plaster to cure for seven days before painting.

Most concrete surfaces are laden with free lime. When cured properly, this free lime is securely trapped inside the plaster, but if the surface is not properly cured with sufficient wetting the lime can be transferred through the topcoat system causing undesirable lime staining. Thin polymer-modified plasters are most prone to the problem as they often dry out during the curing process, resulting in an incomplete cure.

The problem has little to do with the paint or the painter – the problem is the improperly cured substrate. How do we know this? Simple: when the substrate is properly cured, there is no problem. Unfortunately, lime staining only shows up as a problem after the substrate has been coated. Free lime is aggressive and can affect some pigments too. (Application of Resene Limelock can help with colourfastness as well.)

Resene Limelock traps free lime in the cementitious substrate, protecting the paint finish against the appearance of ugly lime staining, and providing a perfect base for subsequent Resene finishes. Part of the surface preparation process, Resene Limelock should be applied as soon as possible over plaster systems to achieve maximum potential.

You can cure and seal the surface using Resene Limelock while the scaffolding is still up, allow it to dry and then start painting on the acrylic topcoats. The job will be finished while others are still waiting seven days before they can start using traditional products. Although if you’re planning dark, heat-absorbing topcoat, Resene recommends waiting seven days before painting just to be on the safe side. 

See Data Sheet D809 for more technical information on Resene Limelock.