Schott Borofloat Gobo Glass

Today I was interested in how glass gobos are made for moving lights.  I started with the Martin website and found the user manual for the Mac 2000 Profile II.  The manual specifies that the gobos be made with high temperature Borofloat glass or its equivalent.  It also specifies that the coating be dichroic or aluminum.

The Borofloat glass led me to a company called Schott.  Schott is in the business of manufacturing glass.  They make glass that is very resistant to breaking and heat.  Their website talks about the Microfloat process.  This process starts by mixing raw materials like borosilicate, and melting them.  This liquid glass is then spread onto liquid tin.  This creates the very flat surface needed in their glass.  It is then mechanically flattened to the desired thickness as it passes through an annealing stage.  Annealing is needed to reduce internal stress in the final glass product and toughen it.

Borosilicate glass also used in our HID lamps because of its strength and heat properties.  This type of glass is also marketed as Pyrex glass found in graduated bottles and cookware.  The Mac 2000 Profile II uses the OSRAM HMI 1200 W/S metal halide lamp, which has a maximum operating temperature of 450ºC.  Also, the glass that Schott makes for gobos has a long-term operating temperature of 450ºC.  This means that the gobo will operate in the temperature range of the lamp.

Finally, thin-film interference is the technique that is used to filter light in these gobos.  The glass is coated with thin layers of metals.  The metals are vaporized in a vacuum chamber with the glass gobo inside.  Through deposition, the vapor crystallizes on the glass in thin layers.  Since the range of visible light is from about 380nm to 740nm the metal layers need to be on this magnitude.  This is essential for thin-film interference.  The distances between the layers will determine which wavelengths reflect and which pass.  According to NASA, the vacuum deposition process for making dichroic glass was developed in the 1950s to protect instruments being sent into outer space.

The idea that the technology used in one application can be used creatively for another is really interesting.  I think it is important to remember that the future of entertainment technology likely exists in a precursor form right now.

OSRAM Arc Lamp

Replacing arc lamp bulbs is something that needs to be done routinely on moving lights with arc lamps.  I found a document online that gives information on how to replace the lamp for a MAC 700 Wash.  Summarizing what Martin recommends for lamp replacement was very interesting and taught me some useful information. 

The OSRAM SharXS HTI 700 W/D4/75 is the specific lamp for the MAC 700 Wash.  Some of the quick facts about the lamp are that it has an average of 750 hours of life and 700 watts of power consumption.  This can be counted in the fixture with a clock that can reset for lamp life, helping someone that services these fixtures at rental shops.  Martin actually says not to exceed 75 hours past the lamp life.  To help with lamp life it is recommended by Martin to let the lamp heat up for five minutes before dousing.  This means that if the lamp has been turned on by accident it is better to leave it running for five to ten minutes before rushing to turn it back off.

OSRAM is the company that makes these specific lamps.  In their documentation I found information like color temperature, which is 7500ºK.  In the Martin fixture there is variable color correction available.  OSRAM also specifies cooling of the lamp while operating to be forced air with a fan.  That seems pretty obvious but it is important to specify on a document describing the lamp.  Finally another interesting fact is that the cold strike for the lamp is 3,000 volts and the hot strike is 25,000 volts.  OSRAM says that the lamp is capable of hot re-strike so long as the fixture can provide the ignition voltage.

There are diagrams that Martin has online to replace the lamp.  Most importantly, time should pass after the lamp is off; 45 minutes is what Martin recommends.  The head of the 700 Wash can get up to 185ºF before a warning message appears.  This means that the lamp is clearly at a much greater temperature than that.  In fact, OSRAM specifies a maximum of 842ºF for the lamp.  Of course, Martin specifies cleaning the lamp with alcohol and polishing it as well.

The two documents were very interesting and straightforward.  They left little to the imagination on how to replace the lamp and what lamp to replace it with.  This is necessary for the correct and efficient operation of lighting fixtures.

http://www.martin.com/service/downloadfile.asp?name=UM_MAC700Wash_EN_D.pdf&cat=65

http://www.osram.com/_global/pdf/Professional/Display_Optic/Entertainment/SharXS_HTI/SharXS_HTI700D4-75-e.pdf

Elation Art SSC Lighting Controller

Elation just released a new product over a week ago.  It is called the Art SSC Lighting Controller.  It is a standalone DMX-512 playback unit with two universes.  It is about the size of two DI boxes next to each other.  It is intended for use in permanent installations where repeated lighting and show controlled devices work.  It has many features that appeal to the turnkey customer.

The input and output features are plenty in this small package.  It has DMX in, MIDI in and out, GPI and an RJ-45 port.  It has the ability to be programmed via an HTML page when connected to a computer.  The best part is the ability to connect a client's computer to it with custom interfaces made for them and password protection so they are locked out of advanced programming options.  This device also has an astronomical clock built in and a battery backup so that DMX and show control data will stay up and running through power interruptions.  The clock can be used to trigger events based on time, date or any other information an astronomical clock provides.

The DMX input port provides the ability to record up to 16 tracks of DMX data.  These recordings then can be programmed to play back as well.  I can imagine that a stream of DMX that a lighting programmer is good at creating, or is only capable of creating on their favorite console could be perfectly recorded and played back by the Art SSC.

The Art SSC can run as a standalone piece of hardware in an installation.  However, it is programmed with an external computer through an HTML page.  This leads me to believe that there is a tremendous advantage for clients and contractors.  The contractor can program a show, or whatever controls are needed with their computer, and the client can control what they need from day to day with their computer.  As long as both computers have a web browsing program and the right credentials to access the device, they can expect good operation.  The Art SSC has no moving parts making it more reliable than hard disk based show control found on computers.

http://www.plsn.com/product-news/8345-elation-art-ssc-dmx-lighting-controller-for-fixed-installs.html

http://www.elationlighting.com/ProductDetails.aspx?Category=&ItemNumber=1794