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UltravioletPhotography

Trying to Prevent Filter Glass Oxidation #1


Andrea B.

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Often (always?) the speed of chemical and physical reactions decrease with lower temperature.

Cool storage will likely improve the situation if the relative humidity do not get too high.

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Looks good Ulf

I just found that the food grade oxygen absorbers are made with steel powder & salt, to cause the steel to oxidise, therefore absorbing the oxygen....

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Argon & Nitrogen are about the same price...a valve should be easy to find....

https://www.ebay.com...&frcectupt=true

 

Perhaps a quick squirt in a deflated bag with the filter inside & a quick deflate again & zip shut.....should do the trick....cheaper then a new filter

 

Perhaps in a small box with foam top & bottom to keep the bag flat & deflated & provide enough pressure to stop the bag self inflating again......

Tell them you saw it here first...;-)

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Gases (especially those with a small molecule) can diffuse through things. Helium has the smallest molecule, being a noble gas (the molecule has only one atom, and the helium atom is actually the smallest atom there is, even smaller than the hydrogen one). You will surely not use Helium, but argon is another noble gas with a monoatomic molecule... Maybe nitrogen is better.
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Stefano... :cool:

If the bag is under pressure from foam top & bottom it wont self inflate & also leave no room for any gas to enter.

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The problem is that gases can escape. A helium balloon doesn't last long because helium escapes. But you are right, what matters is that nothing enters. Unless you want to use mylar... maybe this is going too far.
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Gases (especially those with a small molecule) can diffuse through things. Helium has the smallest molecule, being a noble gas (the molecule has only one atom, and the helium atom is actually the smallest atom there is, even smaller than the hydrogen one). You will surely not use Helium, but argon is another noble gas with a monoatomic molecule... Maybe nitrogen is better.

Argon atoms are almost three times bigger in radius than helium atoms, so the problem will be less pronounced.

It is also heavier than the nitrogen molecule and more efficient for purging air:

https://www.research...t_like_nitrogen

 

To get more secure long time storing I would put filters, with argon, in sealed glass jars, like the ones used for jam, etc.

For short term storage during the active photography period keeping them in gas filled plastic bags can be enough.

With a reasonably big supply of argon it is no problem to re-store the filters when not used, daily if needed.

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The problem is that gases can escape. A helium balloon doesn't last long because helium escapes. But you are right, what matters is that nothing enters. Unless you want to use mylar... maybe this is going too far.

Wouldn't gas loss depend on pressure differences appart from molecule size?

If there is no pressure difference like in a not completely filled plastic bag there is not much driving the argon from escaping and as the oxygen molecule is big it will not enter through the wall.

The main reason for using either argon or nitrogen is to purge the oxygen and water vapour from the container to avoid harming the filter surfaces.

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Wouldn't gas loss depend on pressure differences appart from molecule size?

If there is no pressure difference like in a not completely filled plastic bag there is not much driving the argon from escaping and as the oxygen molecule is big it will not enter through the wall.

The main reason for using either argon or nitrogen is to purge the oxygen and water vapour from the container to avoid harming the filter surfaces.

Yes, pressure does play a role. The ideal solution would be to store the filters in an inert, non-poisonus, non-flammable, denser-than-air gas (like argon), inside a plastic bag or similar, maybe all inside a second container (like a jar), also filled with the gas.

 

Also, nobody mentioned light. Some filters can maybe be damaged by high energy photons, such as UV and HEV (High Energy Visible, about 400-500 nm), so storing them in a dark place would be ideal.

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Andy Perrin
Why has nobody recommended Yucca Mountain yet? Surely the best solution is to bury them far underground to reduce the cosmic ray count? I don’t THINK we have to worry about neutrino damage, but we should consider everything.
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This started out as a great idea to use a household appliance to prevent filters from oxidizing and we're now at lab level talking about argon, nitrogen and pressure levels...
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I wish my grandfather was still around, he would know what to do!

He had a saying:

 

I grow what I can,

I eat what I grow,

I can what I can't eat,

and I eat what I canned.

 

Don't rule out home canning as a possible option for preserving filters!

https://en.wikipedia.org/wiki/Home_canning

 

Picked Filters, sold by the jar, they stay fresh in your pantry for decades without loosing their nutritional value.

post-87-0-24018500-1592930627.jpg

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This started out as a great idea to use a household appliance to prevent filters from oxidizing and we're now at lab level talking about argon, nitrogen and pressure levels...

The original idea with the household appliance might not be that great, considering the risk of contamination from the vacuum bag itself and the not very deep vacuum level those vacuum-devices reach.

There will still be plenty of oxygen left inside to harm the filters. It is not a good idea to let the plastic bag touch the filters surfaces.

 

It is just lab level due to the technical analysis done, likely giving a better result for the storage.

 

The cost levels are not that far apart either.

The vacuum sealer, household appliance with dedicated bags will be more expensive, in the long run, than the big argon bottle I linked to.

 

If the big gas tank is too big for you to handle, you can get a system with smaller 60l disposable bottles:

https://www.amazon.c...=nb_sb_ss_i_4_5

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Yes, as long as an uncoated filter is exposed to oxygen

I think the speed varies with temperature and humidity too.

My filters are not ageing very fast and mostly during the hotter more humid summer period.

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I think the speed varies with temperature and humidity too.

 

The general rule of thumb is: the reaction rate doubles with each 10 degree Centigrade increase in temperature.

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THANK YOU EVERYONE for all the great ideas and comments. It has been fun experimenting with the vacuum sealing idea even though it probably is not a perfect solution. I'm going to follow through on it just to see what happens. I'll store some blue-green glass in a vacuum sealed container and leave it sitting out with some unprotected blue-green glass. I will report what happens (if anything) in 2 weeks, 4 weeks, etc.

For now I added a conclusion at the beginning of the first post stating that the experimental result was not ideal. :wacko:

 


 

It is not a good idea to let the plastic bag touch the filters surfaces.

 

John, it truly depends on what kind of plastic the bag is made from. Although I *definitely* agree it is a real concern and I would require that knowledge before proceeding any further with my vac bag experiments. :smile:

 


 

Cadmium, I love those mason jar filter packs!! I have a bunch of those mason jars used for storing various food items. Your filters look kinda cute in them. The mason jars would prevent excess moisture from reaching the filters. And that is a good thing. :grin:


 

Why has nobody recommended Yucca Mountain yet?

 

Hey, I'll go for it!! I've always wanted to see one of those places. I'd also love to see the seed storage place in Svalbard. Of course the logistics of retreiving ones stored filters from Yucca Mt. are a bit daunting. :tongue:

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These discarded UV/IR cut filters don't suffer from the 'pox', why?

 

Because your UV/IR-cut filters have a more stable chemical composition than does blue or blue-green glass. And possibly some UV/IR-cut filters are coated. It is sometimes difficult to determine whether a filter is coated or not.

 

But trust me on this if you will --> long-term *all* glass will suffer some deterioration from oxidation/moisture or other environmental phenomena. Glass is not a thing which lives forever.

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I think he means the cut filter removed from cameras converted to full spectrum, and yes, those usually have multiple coatings for various reasons, so they generally last the life of the camera.

Those are usually not discarded (by conversion places), just try getting the 'discarded' filter from LifePixel from your FS converted camera, they keep those, sell them, and use them for installing in cameras they convert back to stock.

 

Here is the nitty-gritty. For uncoated filters, the susceptible filters are:

BG filter types:

Schott: S8612, BG39, even BG40 (not as bad), the same applies to the Hoya equivalent versions, and any other brand equivalent versions.

U filter types:

Schott: UG1, UG2A, UG5, UG11.

Hoya: Hoya U-360, U-340, all Hoya U glass.

All U filter glass types, any brand.

Some of the higher IR longpass filters can sometimes show cloudiness also.

 

If you use your filters, we generally clean the filters off with a cloth before we put them on the camera. You will look at the filter then, and you will see any cloudiness, if you do, then that is when you clean it,

take it apart, clean it with hydrogen peroxide, then with cerium oxide (if needed), this will remove the cloudiness if you haven't deferred maintenance for many years.

I have never had any issues with cleaning my filters in this way, however if you don't use your filters for years, then I suggest you check on their condition often, and if you see any signs of cloudiness clean then as I have described.

Clean them on a regular basis, just like other things in life if you want them to stay mint. They will stay mint if you clean them often enough.

 

If you want coated filters, then I would start by contacting ITOS.

I have edited this line of text because I contacted ITOS yesterday and they informed me that they do not carry S8612, a surprise to me.

 

If you want 'clad' filters, then that is available, but also increases the cost, and it is a little more complicated depending on the type of glass you want to clad with.

Some clad is very thin, some transmits deeper but may need to be thicker depending on the pre-lapped thicknesses available.

 

Personally, I prefer the plain glass, just because I look at my filters often enough and actually sometimes not really often enough!

What exactly is enough? That would depend...

Time is not the only factor, local climate seems to be a factor also.

Filter glass doesn't become cloudy on its own by internal factors, that is why clad and coated filters don't get cloudy.

 

I hope that info helps.

The take away, you don't need to worry about this if you maintain your filters, check them and remove cloudiness when it is in the early stages.

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Are we trying to pack these things so they will still be viable when our tomb is opened in 3000 years?

 

YES !!! :lol: :lol: :lol: :tongue:

In the 51st century, the renowned archaeologist S. Spiff will find our perfectly preserved color filters and declare them to be some kind of ceremonial objects used in sun worship and for prevention of evil viruses.

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