1. Each piece of heat resistant borofloat is cut to the desired diameter and thickness. For multi colour gobos dichroic glass is 0.2mm to 0.5mm thick to optimise focusing.
2. Each piece of glass is arrissed and then chemically cleaned to the highest standards.
3. The glass is then coated with a 1 micron layer of chrome or aluminium applied as a vapour at over 1700° in a vacuum chamber. Or, for dichroics, multiple layers* of Titanium Oxide and Silicon which change the frequency of light that passes through. These colours are time consuming and costly to produce but will never fade.
4. Once cooled the coated glass is cleaned and centrifugally coated in a clean room with photo resist, which acts as an etching mask, and then baked.
5. In our Mac studio we rework your supplied artwork and output to an image setter to create a 400lpi film positive.
6. The glass is then exposed, in a dark room on a vacuum bed, to ultra violet light passing through the positive film of your required image.
7. The glass is then passed though into a chemical safe clean/etching room before going through a series of different developing, acid etching and cleaning baths.
8. The resulting piece of etched glass may have 'pinholes' caused by microscopic pits or bumps on the surface of the glass which projected light will pass through.
   
   a) For chrome or aluminium, each gobo is retouched, under a microscope, using a heat resistant silver catalyst ink. These marks will be clearly visible on the finished glass and are there to improve the quality of the projected image.
   
   b) For dichroics we always add another ringed black screen printed gobo to define the edge of the projected image. this gobo is glued into place using silicon in a clean room.
   
   
9. a) For chrome or aluminium etching the gobo is cleaned and bagged. That is the end of the process.
   
   b) For 1 colour dichroics we always add another ringed black screen printed gobo to define the edge of the projected image. This gobo is glued into place using silicon in a clean room.
   
   c) For B/W* + flat, standard un-etched colour we combine a chrome etched gobo with a dichroic filter glued into place using silicon in a clean room.
   
   d) For multiple or special coloured gobos we etch and/or combine as many gobos & filters as necessary to create the finished image. All glued into place using silicon in a clean room.

* The number of layers (bits in the vacuum chamber) depends on the thickness required to allow the desired frequency of light through.

Standard Dichroic Colours
This is the range of 8 Standard OPTI Dichroic colours. Any of these can be used as a straight filter to
colour a black and white image. Some may be etched to create a coloured image.