Steel or glass: choosing a gobo

Updated 8 October 2026

Steel is cut from a thin sheet of stainless steel: cheaper, tough, and limited in detail. Glass carries the image as a coating on heat-resistant glass: finer detail, greyscale and colour, at a higher price and with more care needed.

Steel

A steel gobo is a stainless steel plate with the design cut or etched through it, so light passes through the holes. Thickness varies by maker: Rosco lists 5 mil (about 0.13 mm), Apollo 8 mil, and Goboland 0.2 mm.

The catch is anything that would float. The middle of an O, D or A has nothing holding it to the plate, so it falls out. Makers fix this with bridges, also called tabs: thin strips of metal that tie each island back to the plate. Apollo compares it to carving a pumpkin, and adds the bridges for you. Rosco says tabbing is almost always needed for text. The bridges show in the projection as thin dark lines.

One way to control how that looks is to use a stencil font, which has the bridges designed into the letters. That is our suggestion, not a maker's rule. Gobo Designer spots letters with counters on steel and offers a stencil font as a fix.

Steel suits text, logos and simple shapes. Apollo's rule is that a basic star belongs on metal and a detailed cityscape needs glass.

Glass

A glass gobo has the image as a coating on a disc of heat-resistant glass, so nothing needs bridging: fine lines, floating shapes, halftones and photographs all work. Rosco's black and white glass is 1.1 mm Borofloat. Types vary by maker:

• Black and white (sometimes greyscale): Rosco and Apollo's SuperResolution, Projected Image's Monochrome.
• Colour: dichroic glass in one or more colours, or full colour (Rosco, Apollo ColourScenic, Goboland, Projected Image).
• Printed: Apollo's PrintScenic is for LED fixtures only.

Glass needs heat care. Rosco rates its glass substrate at 450 °C short term and its coating at 250 °C. Apollo does not recommend glass in fixtures above 750 W unless the fixture has heat protection. Hold glass by the edges, like a CD: Projected Image notes that fingerprints and grease can damage it once it is lit.

How long they last

Apollo quotes 100+ hours for its metal gobos and 400+ hours for its glass, and says the figures are not guaranteed because the fixture, use and design all matter. Those numbers are Apollo's for Apollo's products; other makers do not publish comparable figures.

Choosing

• Choose steel for text, logos and bold shapes, on a budget, or in hot tungsten fixtures.
• Choose glass for fine detail, floating elements, photographs, greyscale or colour, or when bridges across your lettering are not acceptable.

In Gobo Designer, set the material on the Fixture tab. The checks then measure your actual artwork on the gobo, after keystone correction, and tell you if steel will struggle.