There are two main technologies for reproducing photographs on a concrete surface. Photolithography (Fotolith) is designed for different concrete setting speeds, and photo engraving (Vectogramm-Technik) is performed using template matrices made on computerized milling machines. Unlike images drawn or printed on concrete, both methods include the building material itself in the process of creating a photographic image, since the photographs are "engraved" on it.
In the first case, the photograph is first transformed into a raster black and white template. By screen printing, it is transferred to a special film of millimeter thickness, but instead of pigment in layers of various thicknesses, a concrete retarder is applied to the film. Where the photoconcrete is supposed to be dark, the concentration of the active ingredient is especially high, and in the light areas, the retarder is less.
This film is placed in the formwork and poured with concrete. The retarder works in specific places, as a result of which the concrete hardens at different rates.
After 16-24 hours, the concrete panels are freed from the formwork and washed with water under low water pressure. Water washes away the top layer, and its surface acquires a different texture: smooth or rough (where there was a lot of retarder, the relief is deeper).
Corresponding to the depth of erosion on the concrete surface, the tone of the image is transmitted. A smooth surface reflects light well and looks light, and shadows appear on the embossed surface - it conveys various shades of gray. With the help of the depth of the relief and the granulation of the concrete mixture, it is possible to regulate the transitions of light and shade and the contrast of the "photograph".
In order to achieve the desired quality, it is necessary to very accurately observe the process technology (for example, the composition of the concrete mixture), otherwise irregular erosion, unplanned irregularities may appear and the photograph will turn out to be distorted and inaccurate.
The size of a panel made of photo concrete, which can be made, for example, by the German company Fabrino (Germany), is 1x2 m. If you need a larger image, then it is assembled from several fragments.
Vectogramm-technik is a method in which information about the image is transferred to the surface of a flexible panel-template using milling, engraving. But first, the photo is processed on a computer and decomposed into 256 shades of gray. The different depths and widths of the cut strokes or pixel dots provide the intensity of light and shade and the rendering of tones.
The resulting model is used as a template to create a photo print on concrete. After stripping, a relief of various depths is visible and from a certain distance, under the influence of light and shadow, you can see the desired image. Changing the viewing angle of the observer and the brightness of the light source provide a new experience. The final impregnation protects the embossed concrete surface from dirt and environmental influences.
An unlimited number of images can be taken with this technology. The international company Reckli develops and manufactures elastic texture matrices Formliners and formworks, as well as liquid two-component cold curing elastomers for self-production of such matrices and formwork. In this way, photoconcrete panels up to 4x1.9 m in size are made. The larger image is made up of several parts. In this way, panoramic images can also be obtained.
