Just curious, how soft is 'soft' glass?
Old 01-24-2017   #1
philipus
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Just curious, how soft is 'soft' glass?

I have a 1950 Summitar (coated, 10-blade) which is pretty dusty inside.

I have just cleaned the aperture ring and was wondering if I should try to wipe the glass surfaces in the two front groups.

I've read that the glass is rather 'soft' and I am wondering how soft that is?

For instance, what about using a clean microfibre cloth, would that affect the surface? And what about a cleaning solution of some sort, like high-% alcohol?

Sorry if this is a stupid question...

Thanks in advance
Philip
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Old 01-24-2017   #2
mpaniagua
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I cleaned mine with lens tissue and lens cleaning fluid, very careful (not rubbing too hard) and didnt had any issue (scratch or marks). Used lighter fluid on a bit of stubborn haze with no problem. But again YMMV, so be careful on the lens.

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Old 01-24-2017   #3
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Special tissue is available for delicate surfaces. It is in use in other industries as well, photography is not primary aplication for it. R.O.R. Liquid is available in camera stores.
How soft is old Leitz glass? Common description is chalk soft. It is accurate description as well.
Check YouTube for instructional videos. Rocket blower, wet tissue, dry tissue, rocket blower and so on. If fungus is involved, use receipt and instructions from available on-line Leica M2, light meter and lenses service manual.
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Old 01-24-2017   #4
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Yes, it's soft by glass standards, but it's not that soft. For example, I rehabilitated a Summar with an absolutely opaque front element. It took many hours of polishing with cerium oxide to get it reasonably smooth and clear, not 15 minutes. Of course, it was obviously soft enough to get that badly scratched up in the first place.
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Old 01-25-2017   #5
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Thank you very much for all this info, it's very helpful. I don't think mine has fungus but there might be a bit of haze. Mainly it's dusty, though, but really quite dusty actually.

I'm not able to find R.O.R. Liquid - could I use something else, like alcohol or such?

br
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Old 01-25-2017   #6
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Wet cleaning is not a problem as long as you wipe gently and not rub with abbrasive material.

That said, I have polished the cleaning marks off of a Xenon with toothpaste and a cotton handkerchief.
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Old 01-25-2017   #7
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Glass is easy cleaned if you are careful.

If it is 1950 1960`s old and coated, send it to DAG where he will do a chemical clean as the coating will scratch if you look at it wrong. You will destroy the lens.
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Old 01-25-2017   #8
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I'm using it for almost decade now:

Google is very effective tool. Here is search return from Google on R.O.R. Liquid.
https://www.google.ca/webhp?sourceid...=R.O.R.+liquid

Another name is Eclipse liquid.

99% alcohol is too aggressive, vodka will leave reside.

Tissue was much more complicated, I have to look at the box:
http://www.edmundoptics.com/lab-prod...pes-ex-l/1504/

Rocket blower:
https://www.bhphotovideo.com/c/produ...ir_Blower.html

Rocket Blower, wet tissue, dry tissue, rocket blower. Repeat if necessary.
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Old 01-25-2017   #9
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Thank you for the further replies, and Kostya for the links. Since my earlier post I have managed to locate ROR Liquid here in Europe so I'll order that.

I considered sending the lens to Wil van Manen but was quoted a price of upwards 150 Euro. The lens is not in such bad shape that his help will be needed, hence my interest in cleaning it myself.
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Old 02-13-2017   #10
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Here is the technique I have used. First try blowing any dust that will come off. Cut some small rectangles out of the cleaning tissue. Lay a tissue in the center of the element, then drop 1-2 drops of cleaning fluid onto the tissue. It will wet and stick down. Use no pressure, let the fluid hold the tissue onto the glass. Hold the end of the tissue and rotate the lens, letting the wet tissue drag, spiraling the cleaning from the middle to the outside. Repeat this several times. The liquid and low pressure should protect the glass. I sometimes do this 5-6 times, and most haze will come off. If the glass is etched, or there are scratches, you cannot remove them. But haze is usually from lube outgassing or atmospheric dirt, smoke, etc. You don't need to apply pressure unless the haze is very tough, and only then after a few runs with no pressure. You don't want to rub any micro grit on the glass.
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Old 02-13-2017   #11
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Quote:
Originally Posted by Ko.Fe. View Post
Special tissue is available for delicate surfaces. It is in use in other industries as well, photography is not primary aplication for it.
The special-purpose tissue I use is called "Kimwipes." Safe for lenses.
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Old 02-13-2017   #12
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Softer than silica grit. Harder than cotton. Harder than chalk, too. As long as there's no grit on the lens, or on the cleaning cloth, it's quite hard to find something that will scratch anything except very early soft coating. The most important things are blowing ALL grit and dust off beforehand, and using a CLEAN cloth or tissue (store it in a ZipLoc or similar). I find chamois leather very good...

I should add: I have lenses up to about 120 years old.

Cheers,

R.
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