Lime-Based Plastering
Use this free downloadable 3-part specification to specify Keim’s lime-based plastering for interior and exterior surfaces.
Lime plastering is an ancient technique that has been mastered by many generations of craftsmen. It offers many advantages over cement-based plasters, including more flexibility and absorption properties.
What differentiates lime from cement?
Lime and cement are the two most common ingredients in plastering. Lime is a natural mineral that has been used to make building materials for centuries. While cement is a synthetic product made from limestone (a type of rock) and clay.
Both lime and cement are composed of calcium carbonate (CaCO3), which can be found naturally within rocks or as crystals under the earth’s crust. However, unlike lime which undergoes a chemical reaction when mixed with water to form hydraulic limes, cements do not have this ability due to their composition.
Lime is a natural material which is made from limestone by burning it in an oven at very high temperatures. When lime burns, it releases carbon dioxide and water vapor. This reaction can be used to make many useful products such as mortar, cement and plaster of Paris. In the case of plastering, lime acts as a binder instead of sand or clay (found in mud plasters).
How long will the lime take to dry?
The high alkalinity of lime plasters makes them excellent for use on damp, masonry surfaces. (This is why it’s important to test your mortar mix with a pH meter and adjust the water content if necessary.)
However, lime-based plaster can be slower than gypsum or cementitious plaster in drying out. As you know from our guide to the different types of plastering, many factors affect drying time; here we’ll go over some common ones so you know what to expect when working with lime-based products:
Temperature – The hotter it is outside, the faster your lime plaster will dry. A humid day will also speed up the process because moisture increases evaporation rates—but if humidity levels rise above 50%, they could impede setting and curing processes by preventing adequate evaporation of excess moisture through capillary action (i.e., drawing liquid upwards along a semi-porous surface).
In general, keep temperatures between 60°F and 70°F when working outdoors during the summer months; in other seasons, try not to go below 50°F if possible! For indoor applications where temperature control isn’t an issue (like basements), just make sure humidity levels don’t exceed 50%.
Humidity – High humidity levels slow down drying times significantly because they inhibit evaporation from surfaces. This means there may be more moisture left behind after curing has finished occurring due to higher rates of capillary absorption than normal.”
For more information and assistance, visit the Keim website at www.keim-usa.com.
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