Heat Absorbing Glass for Omega C-700

Hello all! This is my first post here. Please excuse me if I’m in the wrong place.

I recently bought an Omega C-700 but it seems to be missing the Heat Absorbing Glass accessory (473-121). All my googling has fallen short on finding one to buy, so I’ve started to investigate how to replicate its function with something custom. But in doing that it has led me to lots of other questions.

As I understand it, the Heat Absorbing Glass is used to prevent or mitigate the risk of the negative “popping” or the contrast filter, which is closer to the lamp. I’m wondering how big that risk actually is?

I’m also wondering, what actually is “Heat absorbing glass”? I called a local glass cutter and the person I talked to didn’t really know what I was asking for. They responded by saying Tempered Glass can’t be made as small as 3.5 x 3.5 inches, as I think would be the size used in the Omega. Which leads me to wonder, does “Heat absorbing glass” go by another name that a glass shop would understand?

Last, does anyone have a source for an Omega Heat Absorbing Glass accessory (473-121)? As hard as this has been to find, I’m begging to wonder if would be easier to just go find a different used enlarger on the market that has Heat Absorbing glass included or just has parts more readily available.

Thanks all for your thoughts and input. I’ll keep scouring the forms for answers to my questions too.

Heat-absorbing glass would be glass that blocks most long-wave IR radiation. Here's an example: https://www.schott.com/shop/advanced-optics/en/Matt-Filter-Plates/KG1/c/glass-KG1 Note how it blocks virtually all radiation above 800nm. I assume something a little less fancy than this expensive Schott product is generally used in an enlarger.

Check ebay.

Otherwise, you will get various opinions as to the need for the glass. Will you be doing only B&W? Do you have a condenser or diffusion head?

ic-racer said:

Check ebay.

Otherwise, you will get various opinions as to the need for the glass. Will you be doing only B&W? Do you have a condenser or diffusion head?

Click to expand...

eBay has fallen short too. Only B&W. And a condenser head.

Just try using the enlarger without the heat absorbing glass. You may find you don't need it. It is unlikely that it would be easy to search out some other enlarger that did have it. Many enlargers never had it and people survived; and the average person selling off an enlarger doesn't know if they have it.

The point of the heat absorbing glass is to block IR radiation that would be absorbed by a B&W negative and cause it to bulge ("pop"), losing focus. This is more likely to be a problem with long exposures, dense negatives, and larger formats. In a modern age with pretty fast paper and most people using 35mm, you probably will find that you don't need it.

I don't think you will have an easy time explaining it to a glass shop. Maybe there's something similar sold for windows.

I have had a heat absorbing glass (I think for a Beseler 23C), and about all I can remember of it was that I think it looked a little greenish? There's no markings that would tell you a glass type. To the human eye, it's just a clear piece of glass.

reddesert said:

Just try using the enlarger without the heat absorbing glass. You may find you don't need it. It is unlikely that it would be easy to search out some other enlarger that did have it. Many enlargers never had it and people survived; and the average person selling off an enlarger doesn't know if they have it.

The point of the heat absorbing glass is to block IR radiation that would be absorbed by a B&W negative and cause it to bulge ("pop"), losing focus. This is more likely to be a problem with long exposures, dense negatives, and larger formats. In a modern age with pretty fast paper and most people using 35mm, you probably will find that you don't need it.

I don't think you will have an easy time explaining it to a glass shop. Maybe there's something similar sold for windows.

I have had a heat absorbing glass (I think for a Beseler 23C), and about all I can remember of it was that I think it looked a little greenish? There's no markings that would tell you a glass type. To the human eye, it's just a clear piece of glass.

Click to expand...

Thanks for the reply! I probably will try using it without the glass. My only reservation about that is how close the contrast filter try is to the lamp with nothing in between. In the past I had a Beseler 23C and I remember it had a piece of glass in the filter tray, and this searching makes me miss it.

What is considered a long exposure? 20 seconds? Or minutes?

You can try

http://www.khbphotografix.com/LPL/

They sell the used Omega and the updated LPL version of the C700 they might have glass on hand or know who will cut out the right sized glass for your enlarger. I think of a exposure in the seconds to be on the normal side. Mine usually run 12 to 22 seconds. I don't use heat absorbing glass with my D3, but my Meopta 6X6 enlarger uses a glass negative carrier so I don't worry about the negative buckling. You might want to find out if Omega made a glass negative carrier for the C700.

Paul Howell said:

You can try

http://www.khbphotografix.com/LPL/

They sell the used Omega and the updated LPL version of the C700 they might have glass on hand or know who will cut out the right sized glass for your enlarger. I think of a exposure in the seconds to be on the normal side. Mine usually run 12 to 22 seconds. I don't use heat absorbing glass with my D3, but my Meopta 6X6 enlarger uses a glass negative carrier so I don't worry about the negative buckling. You might want to find out if Omega made a glass negative carrier for the C700.

Click to expand...

Thanks! KHB Photografix Online lists it on their website as out of stock, but I didn’t think of sending them a message about any alternatives. I sent them a message.