Dentro de las técnicas de reproducción heliográfica, denomino ferrografías a la aplicación y adaptación, para realizar obra gráfica artística, del proceso conocido industrialmente como ferroprusiato, cianografía negativa o cianotipia. Inventado en 1842 por Sir John Herschel, consiste básicamente en la reproducción de imágenes negativas por contacto con papeles sensibilizados mediante una mezcla de ciertas sales de hierro disueltas en agua.
Dos son las innovaciones de este procedimiento respecto al método industrial. Por una parte en el método industrial se precisa siempre de un original negativo, sin embargo, he conseguido diseñar un sencillo sistema mediante el cual puedo realizar un dibujo positivo que actúa como negativo al ser expuesto en contacto con las sales de hierro. Y por otro lado he logrado modificar el color resultante (azul de Prusia) transformándolo en ocre amarillo. En suma, dos gamas de color (azul y ocre) obtenidas sin intervención de tintes, ni colorantes y sólo a partir del tratamiento individual de cada una de las estampas. También he ensayado diferentes intervenciones; variaciones en los tiempos de exposición al sol o bajo una lámpara ultravioleta, que permiten controlar el contraste tonal; la doble y triple exposición de ciertas partes de la imagen, que aportan "cuerpo", densidad y matices; y otras manipulaciones que ajustan la definición de manchas y líneas, como son los "desplazamientos" intencionados, lo que otorga al procedimiento de las ferrografías un sin fin de posibilidades plásticas.
FERROGRAFÍAS Y GOMA BICROMATADA
PLANCHAS
Among the heliographic reproduction techniques, I call FERROGRAFÍAS the application and adaptation of the graphic process, known as ferroprussiate, negative cyanography or cyanotype, to make graphic artistic work. This, invented in 1842 by Sir John Herschel, basically consists of the reproduction of negative images by contact with sensitized papers by means of a mixture of certain iron salts dissolved in water.
There are two innovations in this procedure, regarding the industrial method. On the one hand, in the industrial method, a negative original is always required, however, I have managed to design a simple system by which I can make a positive drawing that, however, acts as a negative when exposed in contact with iron salts . On the other hand, I have managed to modify the resulting color (Prussian blue) transforming it into yellow ocher. In short, two color ranges (blue and ocher) obtained without the intervention of inks or colorants and only from the individual treatment of each of the prints. Likewise, variations in the times of exposure to the sun, which allows controlling the tonal contrast; the double and triple exposure of certain parts of the image, which provides "body", density and nuances; and other manipulations that allow me to play with the definition of spots and lines or with intentional "displacements", and that give the procedure of the FERROGRAFÍAS an endless number of plastic possibilities.
There are two innovations in this procedure, regarding the industrial method. On the one hand, in the industrial method, a negative original is always required, however, I have managed to design a simple system by which I can make a positive drawing that, however, acts as a negative when exposed in contact with iron salts . On the other hand, I have managed to modify the resulting color (Prussian blue) transforming it into yellow ocher. In short, two color ranges (blue and ocher) obtained without the intervention of inks or colorants and only from the individual treatment of each of the prints. Likewise, variations in the times of exposure to the sun, which allows controlling the tonal contrast; the double and triple exposure of certain parts of the image, which provides "body", density and nuances; and other manipulations that allow me to play with the definition of spots and lines or with intentional "displacements", and that give the procedure of the FERROGRAFÍAS an endless number of plastic possibilities.
