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UltravioletPhotography

Cleaning of some UV Filters.


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Enrico in one of his excellent articles....

http://www.savazzi.n...tography/uv.htm

Headed, about one third down the page, FILTERS.

He mentions one problem that some UV filters have, & that is a surface deterioration, in humid air, of the UV filters surface.

I have been aware of this problem for a number of years & have experience with it happening with CC1 & BG38 filters, which are similiar.

I had learnt that washing & wiping these filters in a dilute solution ( 3% w/w ) of Hydrogen Peroxide will keep these filters clean & clear.

Col

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I've had one of my Baader blue bandpass filters show some problems - kind of a whitish precipitation on the surface. I was able to remove it by taking the filter from its mount and just using a bit of gentle soap and lots of water. It has been OK since, but I keep an eye on it.
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Thanks Andrea & Alex

Andrea I have tried nearly every solvent, but never soap & water.....:(

Alex, let us know how you go please.

Col

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I was desperate to salvage the filter! Nothing else I had at hand seemed to work. I didn't have any hydrogen peroxide though.
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Soap and lukewarm water works well. I have used that for years. However, the hydrogen peroxide perhaps makes removing stubborn spots or smudges easier? Must try.

 

For lenses, pure hexane (same stuff cars use, by the way, but without the additives) can do wonders. Some repair facilities also use "Windex" or similar ammonia-containing cleaing fluids. I once or twice used that fluid for removal of fungi on a damaged lens surface.

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I tried the hydrogen peroxide method a few years ago on a severely deteriorated BG filter (more than half the surface was damaged), without success. It may still work on minor damage.
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UG-11 filters used to filter light output of Xe-arcs can get pretty bad after a while. Sometimes an isopropanol/water mix and a good scrubbing with a paper towel will remove it sometimes not. When that fails, sometimes a bit of white toothpaste and a little water and rubbing with a fingertip will remove it.

 

I am NOT saying either of these methods is suitable for a camera filter. Just thought it might give insight into the nature of the corrosion.

 

I also can relate that certain order sorting filters in monochromators suffer the same issue. This is in my experience due to improper storage, where an instrument taken into the field was left to long in an air tight case. The same instruments kept at normal lab environment can last years without any filter degradation.

 

Similar conditions I expect that would foster lens fungus are fostering filter corrosion of susceptible glass.

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