Why do my Beseler enlargers have a spacer between heat absorbing glass and condenser?

[xkaes]

I have never run across a heat issue either, but my original question was about Newton's rings -- and if that has anything to do with the spacer ring in between the condenser glass and the heat absorbing glass. I still don't know about that. I can run some tests myself, but was trying to avoid spending the time.

A far as I know, none of the other enlargers I have used, before my Beselers, even had heat absorbing glass -- but they all had glass condensers. So far, all I've heard is speculation about whether the heat absorbing glass is there to protect the condensers, the negative, or both. Regardless of the answer, it would seem that any enlarger, especially with a glass condenser, would have heat absorbing glass in it. Is this the case? Seems like a simple, straightforward question.

[Oren Grad]

Beseler is still in business. Have you tried asking them? Sure, it's possible that the designer of the enlargers is long gone and nobody else remembers. But maybe someone there will know.

[xkaes]

I imagine back in the day CB7's were used fast, hard and hot. Maybe using them for printing spools of medium format? I can't clean glass, dust, insert a 4x5 neg fast enough to have heat issues.

I don't see why a CB7 would run hotter than a 45 MX II. The condenser heads are almost identical -- especially the venting. So assuming the same bulb is being used, I would not expect a difference in heat.

[Tin Can]

I don't see why a CB7 would run hotter than a 45 MX II. The condenser heads are almost identical -- especially the venting. So assuming the same bulb is being used, I would not expect a difference in heat.

You are correct. They are the same design, yet scale is in CB7 favor. More glass, more mass. Larger vents, more area. Bigger enclosure. I use the same bulb.

What is heat absorbing glass? Borosilicate? I have stacks of glass in my Elwoods. Elwood documentation shows they increased the number of heat absorbing glass over time. I think Elwood has plain glass. No condensers.

Perhaps the Beseler upper layer is partly sacrificial and meant to protect expensive condensers from scratches, melted filters, grilled cheese toast...

CB7 is bigger, note the light cones have different paint. Is black better than white paint.

Just so happens I am setting up a new darkroom. Beseler CB7, MXT, 23C III, Elwood 5X7 and a Leica V35. So I am haveing a second look at my inventory.

Adorama has this text, '• The high performance 45M Condenser Lightsource utilizes Beseler's patented "Cone-of Light" variable condenser system to adjust the position of the over-sized 6½" optical glass condensers to maximize the illumination for every size film from 35mm through 4" x 5", yielding exceptionally short exposure times, a cooler film stage and less negative buckling than with conventional condenser heads.'

IMG_0464 by moe.randy, on Flickr

IMG_0465 by moe.randy, on Flickr

IMG_0468 by moe.randy, on Flickr

[xkaes]

[QUOTE=Randy Moe;1415440
What is heat absorbing glass? Borosilicate? I have stacks of glass in my Elwoods. Elwood documentation shows they increased the number of heat absorbing glass over time. I think Elwood has plain glass. No condensers.

Perhaps the Beseler upper layer is partly sacrificial and meant to protect expensive condensers from scratches, melted filters, grilled cheese toast...[/QUOTE]

My heads are slightly different that yours, but that is inconsequential. As to the heat absorbing glass, it looks like typical window glass, but I have to assume that it is there to absorb heat from the bulb since it is on the TOP of the condenser assembly. If you look closely around the edges, you will see a thin brass spacer ring on either head. It's easy to assume that it is more than plain window glass, but that would be a guess on my part. Maybe plain glass accomplishes the task! And since it is built-in, it has got to accomplish more than just "scratch/dust" protection.

Does the heat from a 100 watt bulb actually pose a threat to a glass condenser? Curious minds want to know!

[Tin Can]

I'm out.

[Bob Salomon]

My heads are slightly different that yours, but that is inconsequential. As to the heat absorbing glass, it looks like typical window glass, but I have to assume that it is there to absorb heat from the bulb since it is on the TOP of the condenser assembly. If you look closely around the edges, you will see a thin brass spacer ring on either head. It's easy to assume that it is more than plain window glass, but that would be a guess on my part. Maybe plain glass accomplishes the task! And since it is built-in, it has got to accomplish more than just "scratch/dust" protection.

Does the heat from a 100 watt bulb actually pose a threat to a glass condenser? Curious minds want to know!

If your enlarger still has its original heat absorbing glass then it does not resemble window glass and there is only one correct side that has to face the light source for the glass to work properly to protect your film from excessive heat to reduce popping. However, to get optimal performance from your enlarger and lens the enlarger must be properly aligned at all three stages, negative, lens and baseboard. The film must be in a glass carrier, the lens must be used within its optimal magnification range and at its optimal aperture.

Additionally the film stage must be within safe temperature range and that is why you need heat absorbing glass, if required, and the proper wattage lamp.

[xkaes]

The film must be in a glass carrier, the lens must be used within its optimal magnification range and at its optimal aperture.

That's odd. Beseler only sold one 4x5 glass negative carrier -- that I know of -- for 4x5". I have Beseler carriers from Minox to 4x5" and all of them are glass-LESS.

Plus, my heat-absorbing glass on both my CB7 and 45MX II are factory installed and don't appear any different to me than plain thick glass.

Thanks for the info, but I guess I'm on my own.

[Corran]

The film must be in a glass carrier,

Beseler's (glassless) NegaFlat for 4x5 is fantastic - way better than the glass carrier. The glass carrier IMO is great for if you want to scream in frustration as you see your print yet again covered in dust spots after meticulously cleaning it for the 3rd time trying to make just one decent print. Perhaps you have a hermetically sealed darkroom with a phalanx of air purifiers and filters but for a mere mortal like me I chucked the glass carrier in the bottom of a drawer and never looked back. After really going after alignment on my 45MX earlier this year I can say with confidence that the glassless carrier didn't make any difference compared to the NegaFlat for 4x5 and none of the smaller carriers had any noticeable sag when used properly. I printed some negatives and saw it myself.

[Bob Salomon]

Beseler's (glassless) NegaFlat for 4x5 is fantastic - way better than the glass carrier. The glass carrier IMO is great for if you want to scream in frustration as you see your print yet again covered in dust spots after meticulously cleaning it for the 3rd time trying to make just one decent print. Perhaps you have a hermetically sealed darkroom with a phalanx of air purifiers and filters but for a mere mortal like me I chucked the glass carrier in the bottom of a drawer and never looked back. After really going after alignment on my 45MX earlier this year I can say with confidence that the glassless carrier didn't make any difference compared to the NegaFlat for 4x5 and none of the smaller carriers had any noticeable sag when used properly. I printed some negatives and saw it myself.

The Negaflat can not totally ptrevent popping. But more importantly, if you are so plagued by dust then you still have dust on your film rather then on your glass. By placing your glass carriers in a drawer does not make your darkroom dust free, you would be better off, if possible, in spending some time reducing the dust in your area, do a through damp cleaning on all surfaces. Repaint, if possible with a quality gloss or semi gloss washable paint, cover dust emitting surfaces with a sheet of plastic, install a quality fan that can make your enlarging room a positive air pressure area, make sure all windows and doors are properly sealed,