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Some advice sought, Yashicamat 124G lens


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Hi.  My yashicamat has developed haze on the internal face of the rear taking lens. I've got it out. It looks like a cemented doublet, but the haze is on the inside face - the haze looks like breath condensation, but it's fixed on the lens. I had hoped that it was simply lubricant evaporation, but it cannot be cleaned off with simple lens cleaning fluid and cloth.  I've replaced the lens with another from a damaged yashicamat, but it has the start of gum separation around the perimeter.  I'm hoping it will be ok at apertures smaller than f5.6.  But back to the hazy lens:  any suggestions as to how to proceed.

My thoughts are to go thru the following steps:

1. Try 50:50 hydrogen peroxide/ammonia;

2. If unsuccessful, try pond's skin cream;

3. If unsuccessful, try cigarette ash (not sure how to do this);

4. Finally, cerium oxide, if I can get some.

Any suggestions greatly appreciated.

Regards, Arthur (apiarist1)

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Haze on the forward surface of the rear group is a common problem with Yashicamats. I've no experience of the methods you suggest. I had a Yashicamat with the issue some years ago and had to clean it more aggressively than I would have liked, I used ordinary toothpaste which is very mildly abrasive to get it off.

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Thanks Moto-Uno, but I think I've done it.  John, got to cigarette ash and it seemed to work.  Did not have to proceed to toothpaste.  Also 'Ponds Cold Cream' is no longer in production - I think it contained very dilute NaOH, as an exfoliant, which may have assisted in fungus emoval.  I don't know what it was - seemed only to affect the inner face of the rear element duo. Not fungus, but a thin chalky covering, reminiscent of a residue of evaporated finely crystalline salts.  I don't know what, if any, coating was used, but I understand that magnesium flouride can dissolve with condensation.  Anyway, it will be a while before I can put it back in and test it with film. I had replaced it with a rear element set from another, damaged, camera.  The replacement does have the start of balsam separation around the edges, so it won't last. Thanks again for your advice. regards, Arthur (apiarist1)

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