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UltravioletPhotography

Don't Forget about Filter Maintenance !


Andrea B.

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Schedule Routine Filter Maintenance Every 3-6 Months

 

I got caught up in a whirlwind of life events and did not use my filter sets for about a year. When I opened up my filter case a couple of days ago, I was horrified to see that some of my beautiful blue and blue-green filters (all uncoated and unstacked) had begun to oxidize!! One of them even had a kind of greasy substance in the center. Ugh!

 

Well, horrified I was, but not particularly surprised. I know perfectly well that oxidation can happen with uncoated filters of any color. Typically I have a mid-winter inspection and clean-up so that all filters are examined about every 6 months for signs of oxidation or other problems. Oxidation can advance to the point where it deteriorates the surface of the glass and the filter becomes unusable. Please do be sure to schedule some routine filter maintence for your own filter kit to prolong the life of all those little pieces of colorful glass on which you have spent scads of $€£.

 

Two good oxidation removal methods for UNCOATED filters:

  • Hydrogen peroxide: an overnight bath followed by a rinse and good drying.

  • Cerium oxide paste: polishing with a tiny dab followed by a rinse and good drying.
    Or, you can avoid the rinse and simply wipe the paste off carefully with a microfiber cloth.

If you have a glue-stacked, uncoated filter which is showing signs of oxidation, then using cerium oxide is probably the best way to remove oxidation. I'm always hesitant about completely immersing a glue-stacked filter in the H2O2.

 

If you keep up with the oxidation removal, you can extend the life your uncoated filter glass for years. My Baader Blue and Blue-greens are probably the very worst in my filter kit for oxidation, but they are now about 11 years old and still sparkling give-or-take a few minor scratches from field use.

 

I note for the record that using a graphite-based cleaner like a Lens Pen does not remove oxidation. The Lens Pen just makes a weird squeaky sound on the oxidized area. And the greasy type of oxidation could ruin the Lens Pen.

 

Periodically we do discuss filter cleaning here, but a fresh topic serves as a good reminder. Please feel free to contribute any filter cleaning methods or suggestions that have worked for you.

 

ADDED:

  • added the adjective uncoated where appropriate to clarify above
  • added remarks about cleaning other types of filters below

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Cleaning Coated or Dichroic Filters

 

Sometimes simply brushing away any dust and polishing with a clean microfiber cloth is all that is needed for any filter. If a wet cleaning is needed, then you want use a well-known filter cleaning solution recommended for cleaning coated filters and lenses. Some dichroic filters have a coating over the electronic sputtered, hard, dichroic layer, some do not. And I don't think it is very easy to determine this by looking. So it is probably best to treat dichroic filters as though they were coated.

 

When I do need to wet clean a filter, then for years I have used Formula MC multi-coated filter and lens cleaner on any filter (or lens). Formula MC will remove fingerprints, smudges, sticky nectar, tiny pollen grains and dirt. The cleaning process has two steps: after brushing away anything granular, use a drop of the solution and clean the filter with lens paper or microfiber cloth in the usual gentle, circular manner from center to edge. Then with a fresh lens paper or dry microfiber cloth, gently dry and polish the filter surface. For the record, Formula MC will not remove oxidation.

 

There are other such filter/lens cleaning solutions that are equally good. So add your suggestions below if there is one you would particularly like to see mentioned.

 

These days I no longer use lens papers much. They seem to leave some little fibers behind. Microfiber cloths are my personal preference when cleaning filters or lenses. How about you?

 

[The usual disclaimer: UVP is non-monetized and has no financial association with any manufacturer of photo gear or accessories.]

 


 

In personal practice, I've used the following on dichroic filters: Eclipse, Windex, isopropyl alcohol, soap and water, H2O2 and whichever lens/filter cleaning solution is in-house at the time. But you might want to be more careful with your dichroics than I have been . Also note that dichroic filters can get scratched although I'm again not sure whether it's a coating over the dichroic layer or the dichroic layer which has gotten scratched.

 


Did you know that all glass deteriorates over time?

 

 

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Andrea,

You need to start this post outlining the difference between a dichroic (interference) filter and an absorbing filter, typically with out any coatings.

 

Do not clean your Baader venus U filter with Cerium oxide paste. I don't know what a bath of hydrogen peroxide would do to it either.

 

But your U1, UG5 and even S8612 filters may need this cleaning.

 

Most of the cheap bandpass filters I have are dichroic and will need some special cleaning. My Zeiss microscope lens cleaner has worked and not pulled off color yet from some I have cleaned. But even with that I think you need to be careful as some Astrophotographers have pulled off coatings with it. It seems to be a detergent with some type of unknown alcohol or butane. I was lucky to get my small bottle directly from Zeiss at a product show. There are counterfeit Zeiss cleaners for sale on Amazon.

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Thanks David for reminding me.

I added the word uncoated where needed. :lol:

 

Now I'll add a remark or two in the first post about cleaning dichroic or coated filters.

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My uncoated UG or U filters have held up quite well so far. They do not seem to oxidize quickly like the Blue or Blue-green glass.

 

Same remark for my uncoated RG and IR filters.

 

Brand name filters are not necessarily immune from oxidation. My Kolari UV-pass had a ring of oxidation just in from the edge on one side (but not in the center) and went into the H202 bath last night. This afternoon it has been dried, polished and restored to its usual shiny self. I think the Kolari is coated? But I don't know any other way to remove oxidation than what was mentioned above. Suggestions always welcomed. :D

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Andy Perrin
Can someone here show me a photo of what oxidation on a filter looks like? I have not noticed any, but I don't know what I'm looking for, really!
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You may find this cleaning protocol amusing after your recommend frequency.

 

Oh my! That is quite interesting.

And methinks cleaning telescope mirrors is a whole nother thing entirely from cleaning the filters we use for photography. I would *not* want that job, for sure. That is quite an interesting solution they mix up. Might be interesting to try that for our photo filter use also.

 

I take a very practical approach to photo filter cleaning - especially since my filters get so much actual field use - like out in a field, literally. Or the woods. Or the rocky shore. Or the desert. No matter how careful you are and how hard you try, field-used filters come home dusty, sticky and/or smudged. I've more than once had a pollen-laden bee bump into a filter and leave a sticky pollen mess. (Was the bee warning me away from its flower with that bump? Was it attracted by shiny? Who knows??) And I've had filters fall off or get dropped into dirt, water, mud, gravel, etc. Only a couple of times, though, have I had to replace a filter due to a serious scratch or ding. That statement does not include the stepped-upon BaaderU which met its dreadful end when I tried to get up from a crouch on some desert gravel and lost my balance. Saved the camera/lens/tripod though. And missed the cactus. Can't complain. Could have been worse.

 


Andy, oxidation on a filter looks like a splotchy, filmy layer, like something wet has dried on the surface of the glass. It blocks light and is very difficult to simply rub off with just a microfiber cloth. There is also an oxidation or deterioration phenomenon which looks like a greasy smear which literally will take fingerprints as though a thin film of butter were smeared on the glass. Sorry I can't make any photos for you right now of oxidized filters as I just cleaned them all up these last two days.

 

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  • 10 months later...

That looks pretty well done... but give it a try.

I like to start with the hydrogen peroxide.

Remove it from the ring. Soak it in hydrogen peroxide. Use a container that doesn't transmit light, or put it in a dark place.

Put the filter on a clean PED pad (or clean microfiber cloth), use another clean PED pad (of clean microfiber cloth) soaked with hydrogen peroxide,

and scrub, flip and scrub other side.

Clean with methyl alcohol (methanol) and examine.

If most was removed, repeat.

Examine again.

If all else fails, polish with cerium oxide.

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I would probably not use methyl alcohol after hydrogen peroxide.

But I can't remember what the mix creates. Is it only carbon dioxide (and water)?

 

CH3OH + H2O2 = ???

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Andrea,

We are not in pure H2O2, but 3% with water. If pure, interestingly you can form a highly reactive CH2OH. But that might also require a pH adjustment.

 

To be safe Bill soak that filter for 3 days in 3% hydrogen peroxide. Then rinse with water. Then wipe it down with standard lens cleaner. See if any change.

You may need to carefully polish with cerium oxide.

 

I had a bad UG5 filter. Soaked it for a week in 3% hydrogen peroxide, then polished it and its good now. The 1mm UG5 I wasn't careful with when polishing and cracked it in half. A small chunk of cerium oxide got under and I was polishing too hard.

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Bill De Jager
Thanks for the advice! I don't think I have any of the materials needed so I'm going to need to acquire them. This filter and the other dye-based one from this manufacturer sat around neglected and forgotten for years while I used the Baader-U instead, so another week or two of waiting isn't going to hurt.
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Hydrogen peroxide, very common, any drug store, some countries you have to ask for it, but very well used for cleaning. The household 3% is always available. In the US it is in any grocery store on the shelf, just ask.

The Methanol, get it on eBay, name brand ECLIPSE Optic Cleaner, made by Photosol Inc. (they make the PEC Pads also), little 50ml bottle, or smaller.

Eclipse Optic Cleaner = Methanol = Methyl Alcohol, MSDS (material safety data sheet), page 3, 99-100% methyl alcohol:

http://www.photosol....S-JUNE-2015.pdf

 

Cerium Oxide, buy it in powder or fluid form, get the high grade white stuff, buy it form some place that isn't cutting it with tin oxide or the like,

the Chinese cerium on eBay is well known for cut grades, and pink is OK, but why not just get some white, but even white can be cut.

Easily available on eBay or other glass supply places online.

 

Toothpaste, I would wouldn't use it, it has multiple ingredients, I want to know what is in what I use.

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Toothpaste, I would use it, it has multiple ingredients, I want to know what is in what I use.

 

Cadmium,

You may want to edit that again. Never use toothpaste to clean a filter. Many potential problems there. The silica can even scratch up the filter.

 

Baking soda didn't work for me on tough oxidation. But moving from baking soda directly to hydrogen peroxide did etch my glass filters. Must have been enough sodium hydroxide generated to cause the problem.

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NO TOOTHPASTE! And don't ask me how I know. Ha-ha!! :blink:

 

HYDROGEN PEROXIDE: Use only the 2-3% solution sold "over the counter". Stronger solutions of H2O2 can be quite reactive with other chemicals. There are definitely some household chemicals that you do *not* want to mix with H2O2, OK??!!! (Look it up.)

 

I've gotten some streaking with methyl alcohol. So it seems nothing is "perfect" when cleaning glass. The streaking usually can be polished off with a microfiber cloth in my experience so far.

 

David, I've just noticed my UG5 has oxidized. It seems particularly prone to this? I cleaned all my filters at the same time in the recent past. (Forget exactly how long ago, 6 months at least.) And the UG5 got some oxidation while the others are still holding good. Of course it may have been more exposed recently, who knows?

 

I want to also mention that I've had a filter or two along the way which I could not completely clean up. The color filters can last for years, but you will lose a couple of them along the way.

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Sorry, that was a typo, I have always been against toothpaste for cleaning filters.

But some (won't name names) have promoted it on here for that use.

I would not use it.

 

Long pass filters (what I think you may men by 'colored filters') don't seem prone to oxidation.

UG5/U-330, UG11/U-340, S8612, BG39 seem to be the most prone.

 

If you can't get it clean with hydrogen peroxide, use cerium oxide.

Andrea, have you tried cerium oxide?

 

I use methanol all the time to clean the remaining hydrogen peroxide residue off filters. I clean off the hydrogen peroxide the best I can first, but it doesn't seem to work well.

Yes, the Eclipse (methanol) leaves streaks, but polishing that off with the microfiber cloth removed the streaks and makes a very clean and perfect surface.

 

If you don't want to use the Eclipse, then don't. Just go straight to the microfiber cloth.

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I want to do a YouTube video showing this, but I have never done one before (for one thing), and I don't have anything here right now that has oxidation,

but when I find something I will try to do a video demo.

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Bill De Jager

I had forgotten that household H2O2 is 3%; somehow I thought it was 1%. Problem solved (I should have looked before posting).

 

HYDROGEN PEROXIDE: Use only the 2-3% solution sold "over the counter". Stronger solutions of H2O2 can be quite reactive with other chemicals.

 

As discussed briefly here: https://blogs.scienc...oxide_peroxides

 

I recommend the entire "Things I won't work with" series from Derek Lowe for your amusement and terror.

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I use methanol all the time to clean the remaining hydrogen peroxide residue off filters.

Methanol??? That stuff can kill you, even just breathing it is harmful! It's very toxic!

Excuse the exclamation marks but stay away from that stuff if you don't know what it's capable of.

I really don't see any need to use it when ethanol would suffice.

Use ethanol and keep that stuff locked away.

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You can use what you choose, but I don't think it is that dangerous.

Read about it...

https://en.wikipedia.org/wiki/Methanol#Safety

 

We were primarily addressing the issue of cleaning oxidation from filters, as far as all that goes, the methyl alcohol (Eclipse) can be omitted.

Hydrogen Peroxide and/or Cerium Oxide are the two things I recommend for removing oxidation. The Methanol will not clean the oxidation, it simply helps remove the remaining HP.

So just clean the hydrogen peroxide off with a very absorptive cloth that is suited for lenses and filters, it may take a little longer because of the high water content.

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Nisei,

 

Ethanol is not readily available in many US states. Where it is found, it may be called PGA (Pure Grain Alcohol), Alcool, Everclear, etc. It is the only safe liquid alcohol to consume.

 

I have used acetone as a degreaser and cleaner of filter glass. It evaporates quickly, but it is inexpensive and not tooo dangerous. "There is no strong evidence of chronic health effects if basic precautions are followed. It is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled. Acetone is not currently regarded as a carcinogen, a mutagenic chemical nor a concern for chronic neurotoxicity effects."

 

Workers in some industries seem to be perpetually bathing in acetone. I use basic precautions,

 

Just another thought. ymmv

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