An introduction to Silicate Paints
Pure active silicate mineral paints are bound only with mineral binding agents. They are formed by mixing potash water glass, K2SiO3xH2O with lime, quartz based fillers and mineral pigments.
Once painted onto a wall they absorb carbon dioxide, and the lime-based binders carbonate and water silicate-based binders solidify. They form SiO2 x H2O and K2CO3.
Whilst other pure mineral coatings such as lime paints (aside of Fresco-technique) are only moderately weather resistant, mineral silicate paint coats are considered durable and weather resistant.
Alchemists in their pursuit of the "Philosophers Stone" (to manufacture gold) found glassy shimmering pearls in fireplaces. Sand mixed with potash and heat coalesced into pearls of water glass. Small round panes of water glass were first industrially manufactured for used as windows in the 19th century by Van Baerle in Gernsheim and Johann Gottfried Dingler in Augsburg. Johann Nepomuk von Fuchs made the first attempts to create paints with water glass.
In 1878, the craftsman and researcher Adolf Wilhelm Keim working for King Ludwig I of Bavaria to develop paint with the appearance of lime but greater durability patented mineral paints. Since then, they have been manufactured by the successor company Keimfarben in Diedorf near Augsburg.
In 1894, the company Ludwig Beeck established his business in Breslau with the development and production of pure active silicification mineral paints based on water glass. He achieved inseparable bonding between the coating and microporous substrate with BEECK Pure Crystalline Finish, a mineral paint system suited for particularly valuable historical building materials in interior and exterior areas. These original formulae are still used today for the conservation of built heritage and impress with their large colours diversity and their enormous durability.
New and less expensive synthetic resin emulsion paint, meant hard times for a resolute mineral paint manufacturer during the construction boom of the 1950s and 1960s. Mineral paints were nearly forgotten and structural damage caused by the improper use of synthetic resins on porous mineral building materials increased. Despite the clear trend towards synthetic resin emulsion paints, BEECK’schen Farbwerke and Keim remained true to the development and production of pure mineral coating systems.
Mineral paint contains inorganic pigments, and potassium-based, alkali silicate (water glass), also known as potassium silicate or liquid potassium silicate. When used the pure mineral paints do not form a film paint layer but instead permanently bond to the substrate through silicification.
The result is a highly durable connection between the paint coat and background. The water glass binding agent is highly resistant to UV light. While dispersions based on acrylate or silicone resin over the years tend to grow brittle, chalky, and crack under UV, the inorganic binder water glass remains stable. The chemical fusion with the substrate and the UV stability of the binder are the fundamental reasons for the extraordinarily high lifetime of silicate paints.
Silicate paints require siliceous substrate for setting. For this reason they are highly suitable for mineral substrates such as mineral lime and cement based plasters and renders and concrete. They are only of limited use for application on wood and metal. The permeability to water vapour of silicate paints is equivalent to that of the substrate, so silicate paints do not inhibit the diffusion of water vapour. Moisture contained in parts of a structure or in the plaster may diffuse outward without resistance: this keeps walls dry and prevents structural damage. This addition helps avoid condensation of water on the surface of building materials, reducing the risk of infestation by algae and fungi. The high alkalinity of the water glass binding agent adds to the inhibitory effect against infestation by microorganisms and completely reducing the need for additional preservatives.
Mineral paint coats are not prone to static charging and thermo-plasticity (stickiness developing under heat), which is common for surfaces coated with dispersion or silicone resin, soiling happens less, so fewer dirt particles cling to the surface and are easier to wash off. Silicate paints are incombustible and free of organic additives or solvents. Silicate paints colours are highly stable. As they are solely coloured with mineral pigments that do not fade with exposure to UV radiation.
Silicate paints are based upon mineral raw materials. They are environmentally compatible in manufacture and effect. Their high durability helps to preserve resources and their contaminant-free composition preserves health and environment. For this reason, silicate paints have gained popularity, especially in sustainable construction as well as historic building restoration work.
Commonly three types of silicate paints are distinguished: Pure silicate paint consisting of two components, a colour powder in dry or water-paste form and the liquid binder water glass. The processing of pure silicate paints require great experience and know-how.
Around the middle of the 20th century the first single-component silicate paint was developed. The addition of up to 5 mass percent of organic additives (e.g. acrylate dispersion, hydrophobisers, thickeners or similar) makes ready-to-use paint in containers possible. These are also called "dispersion silicate paints". This paint range is still an active mineral paint, actively binding to a mineral background through Silification. However some cheaper silicate paints have more acrylics added and become passive paints without the same durability.
Since 2002 a third category of silicate paints is known: sol-silicate paint. The binder is a combination of silica sol and water glass. The organic fraction is limited to 5 mass percent similar to dispersion silicate paint allowing for chemical setting and retaining of the silicate specific advantages. The sol silicate paint allows use on non-mineral plaster. For these the bonding occurs chemically and physically. These paints can be applied easily and safely to nearly all common substrates.
A Summary of the advantages of using Silicate Paints
- environmentally friendly, non-toxic applications
- high durability, especially on masonry products, and lightfast
- mineral paints with high vapour permeability
- acid rain resistance
- antifungal properties
- reduces carbonation of cement-based materials
Produced by Womersleys Ltd 09/11/2018
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