Processo de Keim
Content
(Redirecionado do processo de Keim)
Processo de Keim
O processo de Keim foi relatado em 1884 na Royal Society of Arts, em Londres, pelo químico e artesão Adolf Wilhelm Keim, de Munique, como uma melhoria na técnica de estereoquromia anterior de Schlotthaner e Von Fuchs.
O processo
First, the surface to be painted is prepared by removing any damp bricks, overly burnt bricks, or decayed wood, and replacing these, and also removing any existing traces of stucco.The surface is then coated with a mixture of quartz sand, infusorial earth (calcined fossil meal), and powdered marble, mixed four parts to one with quicklime slaked with distilled water. The purpose of this layer is to ensure adhesion of the subsequent layers to the surface. Next, a layer of lime-sand mortar is applied to even the surface, with care taken to avoid cracking. This layer is allowed to dry for up to a year.Once dry, a painting ground composed of white quartz sand, marble sand, marble meal, and infusorial earth is combined eight parts to one with slaked lime, and applied to the surface at a thickness of one eighth to one quarter inch. This layer dries for several days, at which point a crust of carbonate has formed on the surface. This crust is removed with a mixture of one part hydrofluosilicic acid to three parts distilled water, which is brushed on and allowed to dry for 24 hours, after which the surface is rinsed with distilled water.A hardening fluid of one part potassium silicate to two parts water is then brushed on and allowed to dry for 24 hours, before a second layer is applied and allowed to dry again. This surface may be painted immediately, or may sit unpainted for several years.Pigments (selected from a set of thirty-eight) are treated with alkaline solutions of potash or ammonia to prevent color change caused by the alkaline fixative to come. Alternative pigments are best for those that cannot be used with an alkaline fixative.Finally, the completed painting is fixed with an application of "waterglass" (sodium silicate) treated with ammonium carbonate, applied in a fine spray in several layers, until no more is absorbed. The chemical interaction of the fixative with the underlying pigments and ground create a material analogous to marble, and highly resistant to chemical corrosion.O foco de Keim em preparar cuidadosamente o campo de pintura veio de seu estudo de Frescos mais velhos e seu estado de preservação. Keim teria trabalhado por doze anos para refinar seu processo.