Mineral paint

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The technical term mineral paints refers to paints with mineral binders. Whether the coloring substance is a mineral pigment or another colorant is irrelevant for classification as a mineral color.

In deviation from this definition, paints are often referred to in the trade as "mineral paints" if they consist primarily of mineral components; the binder can also be acrylic resin or another non-mineral binder. In the following, mineral paints are not explained in this sense, but in the sense of the technical term.

Lime and silicate

In the area of ​​colors, a distinction is made between two relevant mineral binders: lime and silicate . While lime binders carbonate ( carbonate formation ) under the action of carbon dioxide and water , silicate binders (usually potassium silicate or potassium silicate) bind under the action of CO 2 and form calcium silicate hydrates in contact with mineral reaction partners.

Since lime paints (subject to the fresco technique) are only weather-resistant to a limited extent, they are mainly used in the field of monument preservation and earth building . When mineral paints are spoken of today, they usually refer to silicate paints. These are paints that use potassium silicate as a binder . They are also called water glass colors or germ colors (after the inventor Adolf Wilhelm Keim ).

Pure silicate coatings are very durable and weatherproof. They can have a lifespan of well over a hundred years. An example of this is the town hall in Schwyz , Switzerland , which was given a mineral coating in the 19th century .

history

Alchemists in search of the " Philosopher's Stone " (gold production) discovered glassy, ​​shimmering pearls in fireplaces. Sand mixed with potash and heat melted into water glass beads. The first small, round water glass panes were produced and used as windows. The first industrial production of water glass took place in the 19th century by Van Baerle in Gernsheim and Johann Gottfried Dingler in Augsburg .

The first attempts to produce colors with water glass were made by Johann Nepomuk von Fuchs . Around 1850, a facade painting of the Munich Pinakothek by the painters Kaulbach and Schlotthauer is covered with such colors. However, through the use of non-silicifying pigments (earth pigments), the paintings were washed out of the water glass again.

Mineral paints were patented in 1878 by the craftsman and researcher Adolf Wilhelm Keim and are still produced today by the Keimfarben company as the successor to the Industriewerke Lohmann AG in Diedorf near Augsburg .

Vincenz van Baerle, who Keim relied on as a source of supply for his water glass, also tried to produce silicate paints himself. His experiments lasted years until they were fully developed, and he too finally came to good results and the later Silinwerk of the Chemische Fabrik van Baerle in Gernsheim am Rhein also became a well-known manufacturer. It ceased operations in 2014. In Switzerland, silicates, also for the production of silicate bark, are still produced under the name van Baerle by the van Baerle Group, based in Münchenstein, Switzerland, which has developed from the former Basel branch of the German company van Baerle & Wöllner as an independent company Has.

The trigger for Adolf Wilhelm Keim's intensive research was King Ludwig I of Bavaria . The art-loving monarch was so enthusiastic about the colorful lime frescoes of northern Italy that he wanted to experience these works of art in his Kingdom of Bavaria . But the weather north of the Alps, known to be much harsher, destroyed the art paintings after a short time. So he was commissioned with Bavarian science to develop a color that looks like lime but can be kept for a longer period of time.

Original paintings from the 19th century still exist today. Facades in Switzerland, for example the “Weißer Adler” inn in Stein am Rhein or the town halls in Schwyz (1891), Oslo (1895) or Traunstein (1891) are impressive evidence.

properties

Mineral paints contain, in addition inorganic colorants as a principal component, a potassium-containing alkali metal silicate ( water glass ), the potassium silicate , and liquid potassium silicate or Liqvor SILICIVM mentioned. Coating with mineral paints does not form a layer like other paints, but is inextricably linked to the substrate ( silicification ).

The result is an extremely durable bond between the paint and the base. In addition, the water glass binder is extremely resistant to UV influences. While organic binders such as acrylate or silicone resin dispersions become brittle over the years under the influence of UV and lead to chalking, cracks and, as a result, paint damage, the inorganic binder water glass remains stable. The chemical bond with the substrate and the UV stability of the binder are the main reasons for the extraordinarily long lifespan of silicate paints.

Silicate paints require a silicon- containing base for setting . They are therefore suitable for mineral substrates such as mineral plasters and concrete . They cannot be used on wood and metal, or only to a limited extent. The water vapor permeability (diffusion openness) of silicate paints corresponds to that of the painting surface. This means that silicate paints practically do not hinder the diffusion of water vapor. Moisture contained in the building or in the plaster can diffuse again to the outside unhindered. This keeps the walls dry and prevents structural damage. In addition, condensation moisture on the surface of the building material is avoided. This reduces the risk of algae and fungal attack. The high alkalinity of the waterglass binding agent creates additional security against infestation with microorganisms and enables the use of pot preservatives to be dispensed with completely .

Soiling is less likely because, unlike dispersion or silicone resin-bound painted surfaces, mineral-coated surfaces do not become statically charged and do not become sticky when exposed to heat (no thermoplasticity). Therefore, fewer dirt particles adhere and these are also washed off more easily. Silicate paints are non-flammable and contain neither organic components nor organic solvents ( DIN 18363 Painting and varnishing - coatings 2.4.1).

Silicate paints are extremely color-stable. Since they are tinted exclusively with mineral pigments and these do not change in color due to UV light, the silicate coatings also remain constant in color for decades.

Silicate paints are based on mineral raw materials and are very environmentally friendly in production and effect. Their long service life saves resources and the pollutant-free composition protects the environment and health, so that they are primarily used in the field of sustainable construction .

Types

Today, a distinction is made between three types of silicate paints: The pure silicate paint consists of two components, a dry or water-based paint powder and the liquid binding agent, water glass. ( DIN 18363 painting and varnishing - coatings 2.4.1) The processing requires a lot of experience and know-how. It is particularly widespread in the historical area.

The first one-component silicate paint was developed in the middle of the 20th century. By adding up to 5 percent by weight of organic additives (e.g. acrylate dispersion, water repellant, thickener, etc.), the paint can be supplied ready-to-use in a bucket. One speaks here of so-called "dispersion silicate paints" ( DIN 18363 painting and varnishing - coatings 2.4.1). The range of applications for this type of silicate paint is significantly greater than that of pure silicate paint, because substrates with lower strengths and / or organic components can also be coated. In addition, processing is easier than with pure silicate paint.

A third category of silicate paint, the so-called sol-silicate paint, has existed since 2002. It contains a combination of silica sol and water glass as a binding agent. As with emulsion silicate paint, the organic content is limited to 5 percent by weight in order to achieve chemical setting and the strengths typical of silicate. The sol-silicate paint can also be used on non-mineral plasters. Here the bond takes place chemically and physically. These colors are easy and safe to use on almost all common surfaces.

Web links

Individual evidence

  1. ^ Kurt Schönburg: Historical coating techniques - preserve and preserve . vb Verlag Bauwesen, Berlin 2002, ISBN 3-345-00796-7 , p. 43f.
  2. ↑ Kurt Wehlte: Materials and Techniques of Painting. Volume III, Urania Verlag, 2001, ISBN 3-332-01665-2 , p. 452.
  3. ↑ Message to our customers and suppliers In: silikatfarben.com, website of the Silinwerk on July 29, 2014. Accessed on May 14, 2019.
  4. ↑ Timeline of the history of the van Baerle Group, 1838 - 2019 In: vanbaerle.com, company website. Retrieved May 14, 2019.
  5. ↑ Dr. Ingo Rademacher: The color in the old building coating . In: Restauro-Estra, Callwey-Verlag, March 2007, p. 17f.
  6. ^ Kurt Schönburg: Historical coating techniques - preserve and preserve . vb Verlag Bauwesen, Berlin 2002, ISBN 3-345-00796-7 , p. 193f.