How Is Traditional Lime Plaster Applied Outside Made?

Lime plaster is an ancient type of mortar used in historic buildings, consisting of sand, water, and lime. It was first used around 7000 BC and has long been used to protect masonry and live in historic buildings in the modern age. To make traditional exterior lime plaster, one must mix lime putty, sand, water, and any desired additives. Once the mixture is combined and applied to the chosen surface, it must be wet regularly for several weeks to cure it.

Lime is made by heating limestone in a kiln, leaving only calcium oxide, known as quicklime. When quicklime is combined with sand and water, it creates a durable and workable plaster that can stand the test of centuries. The process involves burning limestone to form quick lime (Calcium Oxide), then slaking the quick lime.

To preserve the country’s plastering heritage, it is essential to understand the materials, unlearning preconceptions, using traditional tools, and examining the original that survives. Lime plaster can be modified to fulfill technical and aesthetic needs, such as protecting masonry and living in historic buildings in the modern age.

In Kerala, lime mortar is traditionally made by mixing lime with sand, a little clay, and water. It may also contain reinforcement fibers like animal hair to strengthen the material. Lime plaster is made by heating limestone in a kiln, leaving only calcium oxide.

In conclusion, lime plaster is a versatile and durable material that can be used in various applications, including historic buildings. By understanding the materials, unlearning preconceptions, using traditional tools, and examining the original plastering heritage, we can preserve this country’s plastering heritage and continue to use it in the construction industry.

What is ancient plaster made of?

The earliest plasters known to us were lime-based, with the people of ‘Ain Ghazal in Jordan using lime mixed with unheated crushed limestone to make plaster. This plaster was used on a large scale for covering walls, floors, and hearths in their houses. The terms “plasterwork”, “plaster”, “stucco”, and “render” are often used interchangeably but have regional variations. In this paper, “stucco” is taken to be a composition that can be applied to the whole or part of a building and can be used equally for plain covering or for mouldings and ornaments. Compositions range from lime and aggregate mixes (with other additives) to gypsum mixes, to cement and sand renders.

Up until the late 1800s, stucco, like mortar, was primarily lime-based, consisting of hydrated or slaked lime, water, and sand, with straw or animal hair often included. Interior stucco was generally made with gypsum, marble dust, and glue. It was often molded into ornamental shapes and polished to a marble-like finish. During the 17th and 18th centuries, elaborate painted figures and ornaments were made with stucco. After ca. 1860, Portland cement largely replaced lime for external renders.

Lime plaster is composed of calciumoxide (lime), obtained by heating calcium carbonate (limestone, marble, chalk, and shells) in a kiln to between 900°C and 1200°C. When heated, it changes to anhydrous calciumoxide or quicklime, sometimes described as unslaked lime or lump lime. When dried and ground to a fine powder, it is called hydratedlime or lime hydrate. The addition of highly reactive forms of silica and alumina, such as volcanic earths, ash or rock, brick dust, or ground iron slags, produces a hydraulic set. Gypsum plaster has been used for renderings and mortars since the time of the ancient Egyptians, as well as moulds, sculptures, and castings.

Modified gypsum plasters were patented in the 19th century as artificial marbles, many of which were cast into slabs for interior decoration. Portland cement was patented in 1824 by Joseph Aspdin and was made by crushing and calcining a “hard limestone”, mixing the lime with clay, and grinding the product into a fine slurry with water. Isaac Johnson discovered that overburnt lumps from the kilns produced a stronger, more reliable product with a slower set. Modern ordinary Portland cement is a hard, grey, impervious material mixed with sand for use as a mortar and a render.

How do you make lime paint for exterior?

To paint a brick wall or brickwork, start with 500ml of water and one cup of hydrated lime. Mix well and add more water or lime to achieve the desired paint consistency. Remember to mix the amount to avoid making putty. The original plan was to remove the garage door and enclose the garage with the same brick and window style. However, research has found contradicting opinions on the benefits of painting brick walls or brickwork.

How to make limewash for exterior brick?

An airless sprayer may be employed for the cleaning of bricks; however, for a more polished appearance, the use of a back brush is advised, ensuring that each brick on the structure is meticulously cleaned.

How was lime traditionally made?

Non-hydraulic lime is produced through the calcination of chalk or limestone, which results in the formation of quicklime (calcium oxide). This is then slaked with water, leading to the generation of calcium hydroxide. In the absence of clay, the resulting calcium oxide is designated as non-hydraulic lime. The formation of calcium carbonate, a process known as carbonation, occurs when carbon dioxide in rainwater reacts with the non-hydraulic lime, resulting in stiffening and hardening.

What is the difference between lime render and lime plaster?

Lime plaster is applied to internal walls using a traditional three-coat system, while external walls require a different product called lime render, designed for exposure to elements. Both plaster and render are commonly used in historic buildings from the mid-17th century to the mid-Victorian period. However, over time, lime plaster walls can deteriorate due to movement, external factors like impact or damp, and structural problems within the building.

Cracks and bulges in plaster can be superficial or localized, and may result from failure of the masonry or timber beneath or wider structural issues. To ensure the condition of your plaster, it is recommended to seek expert advice. Plasterite, with years of experience working in heritage buildings and with fibrous and lime plaster, can view, advise, and survey your property to check the condition of your walls and ceilings.

What is traditional lime plaster?

Non-hydraulic lime plaster, also known as air lime or non-hydraulic, is a soft and flexible plaster ideal for preserving delicate masonry. It sets slowly by carbonation and typically cures in around 12 months. It can stay wet for extended periods in damp conditions, but is sticky and easier to apply to ceilings and laths. The traditional three coat system is recommended for applying lime plasters, as it assumes warm, dry weather and may last longer.

Why is lime plaster no longer commonly used?

Non-hydraulic lime plaster is a caustic plaster with a pH of 12 and requires moisture to set. It requires several days to dry and is affected by industrialization, deskilling of trade crafts, and the widespread adoption of drywall and gypsum veneer plaster. Venetian plaster, a polished plaster, is widely used for wall and ceiling finishes. It consists of a mixture of plaster and marble dust, applied in thin layers using a spatula or trowel. Techniques like Marmorino, Scagliola, and sgraffito can be used to achieve different effects with Venetian plaster.

Marmorino adds marble dust to create a polished marble-like appearance, Scagliola imitates various types of stone, and sgraffito scratches the surface to reveal different layers and create decorative patterns. The number of qualified tradesmen capable of plastering with lime has declined due to industrialization and the widespread adoption of drywall and gypsum veneer plaster.

How to make traditional limewash?

Limewash is a paint made by mixing equal amounts of lime putty and water, aiming for a thin paint consistency. To add color, natural powdered pigments like the Coloured Earth Natural range are recommended. Mix the pigment with warm water to create a smooth paste, then add the coloured paste to the limewash. A maximum ratio of 10 parts limewash to 1 part pigment paste is recommended, as exceeding this can weaken the lime mortar structure.

Unpigmented limewash is clear when applied and turns white as it cures, while coloured limewash is dark upon application and lighter. It is recommended to conduct tests to determine the finished color.

How to make exterior lime plaster?

Lime plaster is an ancient alternative to modern plaster, made from sand, water, and lime. It has been used for centuries to create a rustic look and air purification. It is a traditional choice for plastering buildings, with its natural, rough appearance. To make lime plaster, start by mixing coarse sand with one part of lime, one part of sand, and another one and a half parts of sand. Mix the materials dry for five minutes, then slowly add clean water while mixing. Stop mixing when the desired consistency is reached. Lime plaster is characterized by its natural, rough appearance and is increasingly used for its rustic appearance.

What is the traditional method of plastering?

The conventional plaster application technique entails manual labor utilizing sophisticated methodologies, frequently employing lime, cement, gypsum, or a combination thereof with sand and water to produce a viscous paste.