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Beacon manufacture several different types of glass gobo.
In general they should be handled with care. Although they can withstand tremendous amounts of
heat it is a relatively complex product and misshandling may cause problems.
For B/W gobos avoid touching the mirror coated side to avoid scratching the extemely thin metal
coating. The thin metal is neccesery to be able to produce fine detail and high resolution.
The glass gobos are manufactured by a process involving chemical etching with strong acids and a common problem is etching failure and pinholes. This is one of the major problems in the semiconductor
industry and is a well known problem with this type of process. This pinhole problem is solved by
retouching each picture individually using a heat resistent metallic ink.
The glass gobos withstand the heat from most projectors but it is recommended to use
a fixture with a condensor lens as this filters out some of the heat generated by the lamp and
creates a more even field. Each gobo is individually manufactured and it is difficult to predict
the performance in each case and each individual fixture.
 
Black line gobos are created by coating one side of the gobo with a black, light absorbing layer.
This is done to prevent reflection from the lens being bounced off the face of the gobo and
reflected out of the fixture creating a halo effect around the image. These gobos must be fitted
in the projector with the reflective side towards the lamp and the black side facing towards the
lens.
With these types of gobos it is imperative to know what type of fixture the gobo is to be
used in, to ensure that the gobo can be fitted correctly. You need to determine if the image is
bounced off a mirror (scanner head) or projected direct out of a moving yoke or a profile. If you
have not determined this you may end up with the mirror image of your desired projection rather than a correct reading image. Flipping the image around facing the black part of the gobo towards the lamp is not an option as the image will immediately crack. Ordinary metal coated glass gobos do not have this problem and can be fitted in the projector fitted in either direction.
If a pinhole occurs in the gobo it is possible to retouch the picture by the use of a silver pen
(Aluminium paint marker). Usually most metal paint pens that are found in a paperstore should
work, but they may differ to a certain degree depending of the solution used to bind the ink
Cleaning should be avoided if possible, the use of a paper towel to clean will usually damage the
surface coating.
The B/W gobos can be provided with a 0,5mm thick coverglas which will protect the surface coating
so that a cotton cloth may be used for cleaning. Use of Acetone or other cleaning solutions may
be OK but avoid getting any type of liquid between the glass layers as it will be sucked in by
capillary action.
The color gobos are more resistant to scratches as the top layer is a hard dichroic coating,
however the color layers are very thin and sensitive to force so catching an edge while cleaning
or exerting undue force, will crack a layer. This may not be as disastrous as you may think as
very often the crack in the thin dichroic layer, though visible on the gobo, is often not seen in
the actual projection. However these colour gobos should be handled with great care and avoid
using liquids to clean them as capillary action will suck the fluid in between the layers and may
cause discolouration. The color gobos can also be provided with a protective 0,5mm thick glas to make them more mechanically durable.
In some extremely hot projectors there is sometimes problems with the heatresistent silicone used to mount the color layers. This silicone will deteriorate in extremely high temperatures.
It is reccomended to use condensor lenses and align the lamp for a flat field to avoid hot spots
on the gobo. In most projectors on the market this is no problem but in some cases this could
cause problems.
The use of coverglass protection helps the color layers hold together and is recommended for
better mechanical and temperature resistance.
Correct colour reproduction is a major issue for us and is also a common problem in the printing
industry. As we often only make one or two gobos of the one image it is extremely difficult to
create exact colormatching. When printing a colour picture on paper a pre-print test is often run
to test the colour rendition. The colour gobo technology utilised makes this prohibitively
expensive as it is not a series production process. Each gobo is individually manufactured and
has a certain range of tolerance in its colour reproduction but we are continuously working on improving the quality and consistency of the colors we use.
There are many factors that have a bearing on the end result of the projected image, such as the ambient light levels, the colour temperature of the lamp, the surface that is being projected on etc. Different lamp types create different colours and will change as the lamp ages and changes its colour temperature.
We are continuously improving the quality of the gobo and are workin hard to make a good product
even better. User response and feedback is greatly appreciated and helps us improve our product.
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