P3D Heat Study part 6 of 7 (Recommendations)

[Tom Hubin <thubin@xxxxxxxxx>]

Hello,

Here is part 6 of 7.

Tom Hubin
thubin@xxxxxxxxx
AO Systems Design

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        Recommendations

        The 3mm light blue filters of PSSP projector #1 allow too much 
        infrared energy to pass. They need to be replaced with something 
        that will absorb more of the infrared. 

        While the 3mm light green filters of PSSP projector #2 have no 
        record of damage, I would be wary of using valuable film with 
        them. I do not know how hot film can get before it is damaged 
        but 164F seems hot to me. A better infrared absorbing glass 
        should be considered. I also tested PSSP projector #2 with a 
        single light green filter and a 750 watt BTP lamp, since this is 
        how it is presently equipped. Under these conditions the film 
        temperature exceeded 180F and the film and plastic mount were 
        damaged. This projector has no history of damaging slides. 
        However, the film that I used was opaque black and probably 
        absorbed more energy than most slides. It may also be 
        significant that I ran the test for several minutes.   
 
        Bill Duggan's infrared filters should be replaced to improve the 
        screen image brightness. 

        The Kodak infrared filter, which lists for $19, cannot easily be 
        substituted for a TDC filter because it is the wrong shape. The 
        glass is tempered so it cannot be reshaped easily. Custom 
        mounting hardware would be needed to use the 50mm by 57mm 
        rectangular filter in place of the existing 59.5mm round 
        filters. It may be possible to find a vendor for ready-made 
        filters. You can expect to pay $30 to $50 per filter. I 
        recommend Schott KG3 or possibly KG1 glass for the filter 
        material. I have found several infrared filter vendors on the 
        Internet, but the dimensions of their stock filters are not 
        compatible with the TDC projectors. 

        A large Schott infrared absorbing glass plate can be used to 
        make filters that are 59.5mm round and 3mm thick. A 6.5 inch 
        untempered glass square can be purchased from Schott for $165 
        plus shipping. It can be diamond scored and snapped, like window 
        glass, into four squares. It is also possible to diamond saw it 
        into six pieces. This type of sawing can be done in a stained 
        glass shop or possibly a good mirror shop. Cost for sawing is 
        unknown. If six filters are desired then I will look into this 
        cost. A local eyeglass optician will edge the filters to 59.5mm 
        round then temper them for $20/pair.


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