Silicate chalks
In their composition ( pigment , binding agent and additives ), silicate chalks are purely mineral or inorganic ( silicon dioxide in various compounds as the main component). This distinguishes them from other crayons, which mostly contain organic binders.
application
This differentiation becomes relevant when chalk is generally used on different substrates. So far, chalks u. a. used for creative purposes, for example on paper, cardboard or the like. The pigment abrasion from dry chalks (without fatty components such as wax or oil) must usually be bonded or glued to the substrate with a suitable fixative.
The best-known example of this is pastel chalk . Such pastel painting can only survive indoors and appropriately protected, whether fixed or not. The organic components in the chalk itself, in the image carrier (e.g. paper ) and in the organic fixative ( acrylate , synthetic resin ) are not or only partially weather-resistant and therefore unsuitable for outside use.
Silicate chalks were developed for pastel drawing outdoors, primarily for use on purely mineral substrates, e.g. B. on mineral plaster (building material) , concrete , stone , unglazed terracotta , glass (blasted or etched). On these substrates, the silicate is abrasion with a suitably pure mineral fixative (modified potassium silicate fixed) by spraying. The chemically identical components in the chalk, the substrate and the fixative create a permanent, weather-resistant connection.
Like other chalks, silicate chalks can also be used on other substrates (non-mineral coatings, leveling compounds that contain synthetic resin components, for example; non-mineral or organic such as paper, cardboard, wood). There is an organic fixative (acrylate) for such substrates.
history
The invention and patenting of the mineral paint by Adolf Wilhelm Keim in 1878 was based on the same principle. His idea was to make paintings on plaster as durable as centuries-old frescoes . Keim's mineral paint is still produced today by the Keimfarben company in Diedorf . The components of this paint are (simplified) mineral pigments, mineral additives and potassium silicate as a binding agent. A well-known ensemble example for exterior paintings with Keim'scher mineral paint (late 19th century) are numerous facades in the old town of Stein am Rhein . The lightfast, mineral colors have survived to this day without any significant changes. Silicate chalks contain the original color powder from Keim. These consist of purely mineral, lightfast pigments, which are mixed with various mineral additives in a complex process ( collapse ).
The binding agent of the chalks is water glass . It was already described in Meyer's Konversationslexikon in 1888 as a new painting or binding agent in glass painting. A drawing with silicate chalks e.g. B. on blasted glass is also fixed with water glass. This compound is practically insoluble (except for hydrofluoric acid ).
literature
- Achim Pilz: Silicate coatings: systems, applications, advantages. Deutsche Verlagsanstalt, Munich 2005, ISBN 9783421034953
- Jo Herrmann: Silicate chalks . tape 2 . Palette & Pencil, 2006.
- Lothar Bohring: Silicate chalks . tape 1 . The painter's magazine Die Mappe, 2007.
- Berner Münsterstiftung: Activity report Schützkapelle . 2007, p. 34 .
- Christiane Weishaupt: Get more, replace less . tape 10 . Natural stone trade journal, 2008.
- Thomas Schubert: Colored design of natural stone surfaces in connection with restoration measures. Fraunhofer IRB Verlag, Stuttgart 2010. pp. 19-31, ISBN 978-3-8167-8254-4
- Ingrid Hentschel: The new dress of the chest of drawers . Humboldt University Berlin, 2010.