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Amoni and hydrogen peroxide destroy lens?
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PostPosted: Fri Sep 14, 2012 12:59 pm    Post subject: Amoni and hydrogen peroxide destroy lens? Reply with quote

Please help!
I had lens with little trace of fungus. Fungus was outside on 3-4 marks, inside side was clear (one piece lens/glass). I dissemble camera and lens and put in 3%-5% amonia and hydrogen peroxide the rest. After 14h (in the morning) lens was foggy with bought sides, there is lines like small scratches. Does this solution is abrasive, destroying lens? Can I take of this fog, put the lens in trash or try to polish it somehow? I thy it with alcohol, acetone, hydrogen peroxide again and nothing happens.


PostPosted: Fri Sep 14, 2012 1:04 pm    Post subject: Reply with quote

Generally no i have used the same combo on many lenses but it destroyed teh rear element on a Flektogon for me i donth think the zeiss coating likes it


PostPosted: Fri Sep 14, 2012 1:40 pm    Post subject: Reply with quote

What lens from what camera please? Can we see picture?


PostPosted: Fri Sep 14, 2012 2:22 pm    Post subject: Reply with quote

What you might be seeing is etched lines in the glass from the fungus, these can remain even after the fungus has been removed in some cases. The fungus secretes an acid that eats into the glass if left for a long time.


PostPosted: Fri Sep 14, 2012 2:49 pm    Post subject: Reply with quote

Time is matter with any cleaning material work quickly not left on lens for long time.


PostPosted: Sun Sep 16, 2012 7:14 pm    Post subject: Reply with quote

Yes
H2O2/NH4OH is a pretty agressive and non-selective solvent and should be used with care on lenses.
It can pretty easily dissolve many coatings and lyes are generally able to slowly dissolve some ingriedients out of many glas sorts, which can haze the glas.
NH4OH/H2O2 is very good in dissolving fungus but you should only use it when softer methods (alcohol etc.) aren't working and you should never store glas for a long time in a strongly alkaline solution.
That's the reasons why pure acids are often sold in glas bottles while lyes are always sold in plastic bottles.

Most acids are also able to dissolve many coating-ingriedients bye the way, but are not able to etch glas under such moderate conditions (with a very few exceptions).


Last edited by ForenSeil on Mon Sep 17, 2012 1:39 pm; edited 1 time in total


PostPosted: Mon Sep 17, 2012 7:25 am    Post subject: Reply with quote

Thank you for answers. Lens is (or was) the last beck of biometar 2.8 120 for pentacon six. I was very happy that finally I found that lens and now I destroyed it. If any one have have last beck glass for sell I m interested. Maybe I try to polish mines. Anyone have idea how to do that. I know that is probably worst idea because I will change lens characteristic, but now it is usles so I can experiment. I will post pictures.


PostPosted: Mon Sep 17, 2012 1:35 pm    Post subject: Reply with quote

Srdjan wrote:
Thank you for answers. Lens is (or was) the last beck of biometar 2.8 120 for pentacon six. I was very happy that finally I found that lens and now I destroyed it. If any one have have last beck glass for sell I m interested. Maybe I try to polish mines. Anyone have idea how to do that. I know that is probably worst idea because I will change lens characteristic, but now it is usles so I can experiment. I will post pictures.


Depends on how deep the haze ist. If it's only a few microns you could polish it with cerium oxide etc. of if it's deeper you first have to polish a larger grit and with cerium oxide afterwards. Can't say how much it will influence the IQ. Maybe it will only cause an invisible focus shift.

But you can't use normal polishing cloth for that!
Very good surface is medium soft pitch (called pitch 28) with creasing. You can melt ptich carefully until it's like thick honey an then cast it with onto the lens with an anti-slide mat between them to get the greasing. Heat them both slightly before every use, that you polishin tool will fit perfectly.
http://www.youtube.com/watch?v=4f9RJnB_TFU skipt to 0:20 for an example

Hobby telescope makers are using that or similar techniques for polishing their mirrors after grinding. Google will provide much more information. Depending on your country it might be easy to get all the stuff needed and not very expensive (~35 here in Germany for a whole mirror-grinding set with many extra stuff).

I'm planning to make an own cassegrain mirror lens from since a few weeks bye the way, which is the reason why I have some clue about polishing and grinding glas Smile


PostPosted: Wed Sep 19, 2012 8:40 am    Post subject: Reply with quote

Thank you very much for answers. I will try to make pictures and post it here to see how it looks. I think the haze is not deep at firs look it look more like strange mineralization that this chemicals produced (I was hopping that Smile
ForenSeil I wont to try something that is for really micro fine polishing, what is what you thinking? I found thid on ebay it's look interesting it is some liquid with cerium oxide? http://www.ebay.com/itm/3-75mm-DIY-Glass-Polishing-Repair-kit-Light-Scratches-/140766665273?pt=LH_DefaultDomain_3&hash=item20c658da39#shId


PostPosted: Wed Sep 19, 2012 11:52 am    Post subject: Reply with quote

Zeiss uses cigarette ash for fine polisher


PostPosted: Wed Sep 19, 2012 1:29 pm    Post subject: Reply with quote

Might work. Not that expensive. I would try it