The aspiration to bring together industrial manufacturing and traditional handicraft has been a consistent theme throughout the younger history of architecture. In the case of the metallic cladding of the hospital pharmacy at the cantonal hospital in Aarau by Steiger Concept, this seemingly inconceivable combination has been achieved on a small scale.
But from the start: the hospital pharmacy building of the Aarau Cantonal Hospital from the 1980s had to be renovated and remodeled. To accentuate the compact and cubic character of their building, the architects have ''hidden'' the joints between the sheets with folds to the outside, as project manager Sabina Bogacz explained at the Brownbag lunch on 10 June. For this, they had a metal plate pushed under a pronounced, three-dimensional upstand at the edge of the other plate. This way, the joint between the panels vanishes.
Moreover, a broom finish was supposed to give more body to the thin material. This irregular texture, created with a broom pulled by hand, serves as an example of craftsmanship and visual reference for the architects. With this image in mind, or rather with their own samples, Steiger Concept approached the paint manufacturer KARL BUBENHOFER (KABE Farben). "Because a paint application like that is made of a primer and topcoat, we couldn't just pull the right colour off a shelf", remembers Marco Capizzi, Head of Application Technology at KABE, during the event. Because in the dips of the powder layer the primer becomes visible after the broom stroke, which changes the colour tone. In elaborate tests, known as bonding, KABE has applied various quantities of effect pigments - invisible to the naked eye - on the powder coating particles. Until the right mixing proportion was found. The technology of solvent-free powder coating is complex, but it protects aluminium and steel from atmospheric influences: Before coating, the components are degreased, rinsed with water, made more resistant to corrosion without chrome and then dried. Afterwards, they are taken through a coating line, whereby the electrostatic charge of the powder ensures that it sticks to the workpiece.
Being able to view, feel and examine the samples - the reason for existence of the sampling center.
After the powder coating, however, the work was far from done and for Luigi Gelsomino, owner of Traub Powder Coating Plant in Kreuzlingen, it was only just beginning: " A broom finish on metal on a large scale was new territory for us," says Gelsomino, "but the handwork made sense because there were so many different shaped elements to work on".
The treatment with the broom requires a lot of manual skill, the right hardness of the bristles and the pressure of the broom on the metal play an important role for the final result. After several experiments, the coating professionals from Traub quickly got a handle on this. The result surprises with a haptic and visual power: You want to touch the metal and feel the traces left by the broom with your fingers.