[alt-photo] Re: repairing scratch in the glass over the vacuum frame

[Nelson Mark]

I used 1/4 " plate glass and had the corners rounded and all the edges ground with a slight rounding.


On Jan 29, 2012, at 10:52 AM, Richard Knoppow wrote:

> 
> ----- Original Message ----- From: "Earl Johnson" <earlj at comcast.net>
> To: "The alternative photographic processes mailing list" <alt-photo-process-list at lists.altphotolist.org>
> Sent: Saturday, January 28, 2012 9:58 PM
> Subject: [alt-photo] Re: repairing scratch in the glass over the vacuum frame
> 
> 
>> I have replaced the glass on both sides of my flip top Nuarc with Ace Hardware window glass with no apparent decrease in exposure times. On my unit, the glass is held in place by screws that are easily removed with the correct Allen wrench (hex key).
>> 
>> Earl Johnson
> 
>    My only experience with this was replacing the missing glass top on a military contact printer (forgot the name) which uses a group of argon lamps as the source. I made a crude measurement of the UV transmission by looking at the fluorescense of the brightening dye used in paper. I used thin plate glass, it was obvious that the glass attenuated the UV significantly. The printer also has a diffusion glass, the original was cracked but servicable after repairing with optical cement. That has no noticable UV attenuation. The glass I got for the top is green when looking at the edges, the diffusion glass is clear. I did not attempt to find glass with good UV transmission although I think such glass is available for special uses such as green houses. The UV transmission is sufficient for normal silver-gelatin contact paper. There were no bits of the original left so I don't know what its characteristics are. I doubt if this printer is intense enough for use in any POP alternative printing process.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
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