Why Grade Decides the Life of the Piece
The material carries the whole piece. A mirror sphere is a thin shell, so corrosion does not just mark the surface, it destroys the reflection that the work depends on.
The grades used for sculpture work are mainly 316 and 316L, 304 and 201. In practice 304 covers indoor sculpture. For coastal cities and areas with acid rain, 316 is specified because airborne chloride and acidity attack the lower grades much faster.
Compared with 304, 316 is a permanent material with better corrosion resistance and durability. For outdoor sculpture we recommend 316 as the default. We do not recommend 201 for sculpture.
Wall Thickness
Hollow spheres are produced from 0.6 mm to 6 mm wall thickness. Thin walls keep weight and cost down on small decorative balls. Larger diameters, public locations and anything that can be touched or climbed on need the heavier end of the range.
Custom stainless steel balls are commonly produced between 1 mm and 4 mm. Spinning is the route that gives the thickest wall sections.
Other Metals We Work in
Hemispheres are produced in stainless steel, carbon steel, brass and aluminium. Spheres can also be fabricated in mild steel, which leaves a smooth unfinished surface with all welds ground back, ready for painting or for letting the piece rust naturally.
Corten weathering steel is used where the patina is the finish. It resists alkali, acid and corrosion and carries high tensile strength, which is why it appears so often in outdoor landscape work.
Specification Reference
| Sphere diameter | 19 mm to 5000 mm |
|---|---|
| Wall thickness | 0.6 mm to 6 mm |
| Stainless grades | AISI 201, 304, 316, 316L |
| Other metals | Carbon steel, brass, copper, aluminium, corten steel |
| Finishes | Mirror polish, Mill finish, Brushed, Electroplating, Sandblasting, Etching, Silk printing, Spray painted RAL colour |
| Forming | Water pressure forming, mould pressing, spinning |
| Freight limit | 7 feet by conventional freight |
