Archived posting to the Leica Users Group, 2000/11/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I don't own a Thomas safelight, but I have worked in labs that use them. In every case, the filter doors were open and the raw sodium vapor lamp light was being emitted. The light WAS NOT being filtered by the filters. So if this is the normal operating mode, "how can aging filters effect anything?" Thanks, Jim At 04:51 AM 11/16/00 -0800, Frank Filippone wrote: >Ian, Mark et al...... > >The bulb emits all kinds of wavelengths, some of them in the spectrum of the >paper. The filters knock down most of those. The Thomas light is known to >be good, but there is lots of evidence that the old ones will fog. This is >due, in most cases, from filters that have been bleached by the light and >lost their filtering capability. I have had my filters replaced whwn I >replaced a bulb. At that time I discussd the problem and they discussed >with me the filter ageing/bleaching issue. Certainly the new filters wwere >different and deeper color than the older ones. The replacement program is >to send in the filters, whereby they replace the filter element and return >the glass + filter back to you. You can also order whole new assemblies. > >Squirrel away this data until you find your light is fogging the paper ( the >3 minute test has been quoted, I prefer the 10 minute test). Then you can >use this solution or find your own. > >Thomas has no WEB page, Phone number can be found only using the address on >the light... they are located in New Jersey,as I remember...... > >Frank Filippone >red735i@earthlink.net