Mirror ball – ILA Berlin

With a sphere diameter of 3 metres, ACCENTFORM produced the world’s largest one-piece mirror ball for the ILA exhibition in Berlin. The idea was to reproduce a mirror-image and distorted lettering on the ceiling of the exhibition hall through the mirror ball in such a way that the lettering on the ball appears straight, while all other images in the ball appear distorted.

The production of mirrored objects requires high technical manufacturing expenditures and a very exclusive know-how. Mirrored surfaces do not forgive the slightest mistake. Every spot, every unevenness is immediately visible due to the mirror effect. That is why every step in the production of the mirrored sphere requires the highest quality workmanship.

First, the 3m – sphere is laminated from two halves with a wall thickness of approx. 4 mm in glass-fibre reinforced plastic. Then the two halves are assembled to form a sphere. In order to hide the seam permanently and safely, the area is sanded from the outside and covered with an additional GRP laminate. The raw sphere is then annealed for hours at approx. 75° Celsius. The annealing process (heating over a longer period of time) causes the air bubbles trapped in the laminate to expand and become visible on the surface of the sphere. These defects are pierced and sanded out during the annealing process. These defects are then filled. At the same time, the annealing process results in “post-curing”. The high temperatures stimulate the non-cross-linked molecules to bond. The proportion of chemically unbound molecules in the fresh GRP laminate can be up to 3 %. After annealing, the laminate is cured to such an extent that no more deformation due to “creep” can take place in the long term. Only now is the basis created for levelling out the smallest geometric unevenness by filling and straightening. The sphere is then given a coat of filler, which forms an initial barrier between the GRP laminate and the subsequent mirror coating.

The further processing of the mega sphere then took place at the Blach company in Ansbach. For decades, Blach has specialised in mirroring the surfaces of works of art, vehicles and luxury products. Products that are mirrored using a chemical spraying process must be completely rinsed with an aqueous solution during the mirroring process. Thus, the sphere had to be picked up and rotated by means of an oversized skewer.

 

Als erster Schritt erfolgt eine Vorlackierung um eine glatte Oberfläche zu erreichen. Diese vorlackierte Oberfläche wird nochmals nass geschliffen um kleinste Unebenheiten und Einschlüsse zu beseitigen. Anschließend erfolgt der Auftrag eines Grundlackes, der eine brillante Oberfläche bewirken soll. Darauf wird die chemische Metallisierung mittels Silber- Kolloiden aufgebracht. Die Silber- Kolloide bestehen aus kleinsten Silberplättchen die nur wenige Moleküle dick sind. Diese Silberplättchen scheiden sich an der Oberfläche des Grundlackes ab und bilden die eigentliche Spiegelfläche. Jegliche Verunreinigungen und Störungen an der Oberfläche bewirken, dass die Silber- Kolloide sich nicht eben ausrichten und dadurch die Spiegelfläche matt wird. Diese Fehler sind nicht mehr zu korrigieren, als Folge muss das gesamte Bauteil nochmals abgeschliffen und einen neuen Grundlackaufbau erhalten. Nach der Verspiegelung erhält die Oberfläche, die aus reinem Silber besteht, einen Klarlackauftrag. Der Klarlack soll das Silber vor Korrosion und mechanischen Beschädigungen schützen. Die Kosten von verspiegelten Oberflächen können bis zu 1.500,- €/m² betragen.
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