Recipes for Lime Plasters and Renders | The Earth Pigments Company

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Lime Coatings

» Lime Plasters & Renders

Contents

Introduction
Coloring Lime Plasters and Renders with Pigments
Proper Atmospheric Conditions for Application of Lime Renders

Introduction

The warm glow of a polished lime plaster wall

It is in the use of lime that the beauty of Ocher is fully realized, from rustic, textured walls to highly polished plaster finishes. The additional light refraction from the lime crystals along with the texture of the Ocher makes the combination unmatched by any synthetic render. Colored plaster in the finish coat eliminates the need for painting and creates a feeling of warmth for both interior and exterior finishes.

Lime plaster is created from processed lime, water and aggregate in proper ratios. Once applied, it undergoes a critical process called carbonation where the lime reacts with the carbon dioxide in the air, causing it to return to its original form-limestone. In order for lime plasters to succeed, certain rules must be followed in order for carbonation and proper adherence to occur.

Coloring Lime Plasters and Renders with Pigments

Building facade with pigmented lime plaster walls

Pigments have traditionally been added to lime coatings according to local availability. Today, artists and decorators have a huge palette to choose from. Ochers and earths produce warm shades and are permanent to UV. Oxides produce cool shades and are often used in small quantities with Ochers to create different colors such as can be found in our Mineral Pigments which are 90% Ocher based.

To obtain colored lime plaster, Ochers and pigments can be added in ratio to the weight of lime to be employed, before the addition of any aggregate. This ratio should not exceed 20%. If using lime putty rather than hydrated lime powder, half the weight of the putty should be calculated. To mix, slake the pigment in an equal volume of water to create a homogenous paste. This can then be added to the wet plaster mix. The use of a mixing paddle attachment is recommended. When adding pigment color to plaster, it should be considered as an aggregate. Therefore it may be necessary to adjust the water to your mix, particularly when using Ochers. Rather than adding additional water, it may be sufficient just to thoroughly saturate the substrate before application of the plaster, and if necessary, light misting of the plaster with water while it is being worked.

Proper Atmospheric Conditions for Application of Lime Renders

Proper temperature and humidity are required for the carbonation process to be successful.

Temperature should not be below 41 ºF (46 ºF for dark colors) at any time during the application or carbonation process. Do not allow freezing to occur.
In temperatures above 86 ºF or in very low humidity, surface and subsequent coatings must be misted with water.
Exterior coatings should be protected from wind and sun to protect from drying too quickly an opaque covering such as damp canvas or burlap works particularly well.
Surfaces must not have a surface temperature below 41 ºF (46 ºF for dark colors) and must not be excessively hot or excessively wet.
The most critical period of carbonation is the first two to three days.

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