Trying to Prevent Filter Glass Oxidation #1

[Andrea B.]

ADDED CONCLUSION on 23 June 2020: The vacuum sealed bag experiments showed, so far, that it is not easy to get all the air removed because of pump weakness in home-use vacuum bag sealers and/or because of altitude or other environmental factors which affect vacuum creation. Nevertheless, it is possibly a better way to store clean filters long-term than simply storing in filter boxes.

 

ADDED REFERENCE on 25 June 2020: I think I've found a better solution for filter storage and cleaning. Please see the big blue links in this topic: Trying to Prevent Filter Glass Oxidation #2

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I think I have a goofy cool possible solution for preventing filter oxidation??

 

My solution is only useful when storing filters for a prolonged period of time. My solution is probably not particularly workable for day-to-day usage of filters during a short-term photography event or or a photo shooting season like UV-in-the-spring.

 

Vaccuum pack? your filters for long-term storage using one of the home food storage vacuum devices such as this: https://www.amazon.c...F8&node=1090768

 

WHY DIDN'T I THINK TO TRY THIS BEFORE. GEEZ!! DUH!!!

I *actually* have one of these gadgets which my sister sent me for a Christmas present. We use it to seal food before freezing.

 

I'm going to vacuum pack my Baader color filter set which I almost never use. Then I'll let you know how it went. And provide a photo of the vac packed filters.

 

There is a possibility that if the filters could break or warp under the vacuum suction. But I don't think that is going to happen. At least not with the vac sealer I have.

 

I have no way to recommend which of these vacuum sealer devices is the "best". So look for reviews and read up on them before spending any money.

 

Stay tuned and I'll be back soon with a sample vacuum pack.

[Andrea B.]

OK, here is what I've learned so far.

 

After cleaning the filters, I put them into the vac bag and vac sealed them. EZ PZ. No breakage or warping.

 

1) It appears as though perhaps not all the air was removed? from the vac bag I used because of the filter mounts and because of the vac bag thickness. There seemed to be some air left around the inner surface of the filter mount? I'm not sure of this because I don't know how well these vac sealers really work. I have some vac bag film which can be cut to size to make a vac bag and which is thinner. I'll try that next.

 

2) Of course the plastic of the vac bag presses against the filter glass except for a small peripheral area. So, the natural questions are: Will the plastic be harmful? to the filter if pressed tightly against it? Do plastic vac bags and filter glass chemically interact over time? I do not know the answer to this. Prevention of air contamination is no good if plastic contamination could happen.

 

3) My vacuum sealer has a container accessory (photo soon) into which the filters could be placed to avoid plastic film against glass. This might be the way to go. I will try this also.

[Andrea B.]

Snapshot of vacuum sealer. On top of it is a box of plastic film on top for custom-sized bags. On top of the box is the plastic container which came with the set. The air is pumped out through the grey seal on top.

I've never used the container. Forgot I even had it until today. I wonder what keeps the food from being sucked to the top of the container when the vacuuming is running?

 

Snapshot of 5 vacuum sealed Baader color filters. (The 6th had some oxidation so I didn't want to seal it up just yet.)

[Andrea B.]

Re-thinking the warping question. As mentioned above, no evidence of it at the time of sealing. But, long-term would there be stress from the vacuum sealed plastic bag which could cause warping of a metal ring? I suppose you could make assumptions about equal pressure on both sides of the filter mount, thus no warping. But I'm having trouble convincing myself that all the air got sucked from the bag.

[Andrea B.]

I tried a custom vac bag using the plastic film (in the box) which appears to be slightly thinner than the zipper bag I used the first time. Not much difference though in the final look of the filters in the custom bag.

 

I'm still thinking that this vacuum sealing method might be the way to go for long-term filter storage. It's got to be better than just storing the filters in a filter box? Yes? No?

 

It's really hard to say whether or not the filter boxes I have are "leaky" and pass humid air or whatnot. The good clear circular filter boxes certainly do not seem like they would be leaky. All filter boxes have air in them however. And air and filter glass react over time. So there you are.

 

How can I test vacuum sealed filter storage?

I suppose I could leave the vac sealed filters somewhere together with an unsealed and unboxed filter and try to see how oxidation progresses (or doesn't). So I wonder how long that would take?

 

Added: Elsewhere I have mentioned that I've seen clean BG filters begin to oxidize in as little as 6 weeks under warm, humid, coastal salt-air conditions if the filters are not cleaned and reboxed daily.

[Andrea B.]

somebody tell me if I am spitting into the wind here......

[SteveE]

Put the filter in a filter case that has some holes drilled in it? Probably a square one like Hoya filters come in, rather than the round screw together type, so you could drill the holes in the sides of the case so the plastic of the vacuum bag doesn't block the holes as much. In any event, there will be much less oxygen available to react with the filter.

[Nisei]

Great idea Andrea!

I'm sorry I can't answer any of the questions you're having.

But I was just thinking, since we're already in kitchen territory anyway , perhaps keeping them in a container submerged in a liquid of which we know won't hurt the filters might also be an idea. Rubbing alcohol perhaps?

[Andrea B.]

Steve, yes, an aerated filter box would prevent possible warping. I've run the vac sealer about 4 times today on my Baader color filters. So far no warping is apparent. But we have to keep the possibility in mind.

I think the vacuum container I showed in the photo above solves the warping problem. But see my last comment in this post.

 

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Nisei, you are describing the "pickling" method of filter storage. Grandma's Little Jar of Pickled Filters!

Love this idea, but don't know if it is feasible without lots more research. The chemical properties of the metal rings and the glass should be known to determine whether the immersion liquid would be harmful over time. I do not remember enough Chem 101 to have any idea whether alcohols would serve for this. Household alcohols certainly do not harm the glass and plastic containers they are sold in. But alcohol is not sold in colored filter glass with metal parts. Anybody want to run an alcohol immersion test on an old scratched filter??

 

[Alcohol is still difficult to find in some areas in the US. Please, nobody should make use of their sanitizing alcohol to run a filter test. We have such supplies returning to the shelves here but it still sells out quickly. If I can get some, then I'll try this.]

 

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I am wondering whether Schott or Hoya or any other manufacturer of color filter glass would be able to suggest how best to prevent oxidation degradation? I have googled around all afternoon and really not found much info about color filter protection.

 

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Vacuum sealing and altitude. This is partly my problem in the current experiment. At this altitude I cannot hope for a complete vacuum seal with a simple home-use, food grade vacuum sealer. And too, some of the vacuum pumps are better than others depending on the vac sealer brand.

However dot dot dot pause inhale exhale ----- I still think a vacuum sealed blue-green filter might be less prone to oxidation. Do you think so??

[Andrea B.]

Vacuum seal unmounted filters?

If you had the patience, you could remove the filters from their mounts before vacuum sealing them. Doing this would provide for a close fitting seal against the glass. But this also adds a layer of annoyance to the process because it is not always easy to get the filter glass out of its mount. Sometimes glue or "pipe dope" has been used to prevent the filter from loosening in its mount. And the retainer rings used for some filter mounts are thin and light, easily warped. Finally, when you wanted to use the filter, you would have to put all the parts back together again.

 

I can already tell you that I would be too lazy follow through on this type of vac sealing more than once!

[Andrea B.]

Oxygen absorbing packets. Might be useful to add one to the bag or container to be vacuum sealed. Don't put it against the glass, of course.

And it makes sense that a silica gel packet could also be useful.

These packets suggested by Col in another topic.

[SteveE]

Replace the air with an oxygen free gas? Nitrogen would be ideal, but probably hard to do at home. It is a thing to fill your tires with nitrogen, because the nitrogen molecule is bigger and doesn't diffuse through the tire as easy as the oxygen in the air. Perhaps a box with a tire nipple on it where you could go to the tire store and get it filled with nitrogen. CO2 would be easy to get, but is probably too reactive to use.

[ulf]

Replace the air with an oxygen free gas? Nitrogen would be ideal, but probably hard to do at home. It is a thing to fill your tires with nitrogen, because the nitrogen molecule is bigger and doesn't diffuse through the tire as easy as the oxygen in the air. Perhaps a box with a tire nipple on it where you could go to the tire store and get it filled with nitrogen. CO2 would be easy to get, but is probably too reactive to use.

I think this is the best alternative.

Nitrogen or even better argon are good candidates for replacing air.

I think a food-vacuum storage machine will not remove enough oxygen.

 

Argon is used as a protective gas during some types of gas-welding.

Sources available for refilling the pressure bottle as gas-welding are rather common.

 

Protection from oxidation and humidity are rather common problems in many industrial and scientific processes.

I remember that nitrogen or argon was eventually used to protect the super thin vacuum evaporated silver layer on the glassmasters. (used for producing stampers in the CD-industry)

Often the mastering facilities was not at the same place as the CD-factories. Shipping and storing glasmasters before running the galvanic process, making the stampers was problematic as the silver deteriorated after some days.

[Cadmium]

I like how they look in the bag, they make me hungry, the different colors must be different fruity flavors, but you would need a Fruitometer to know for sure.

[colinbm]

What research has Mr UVIROptics done to find a solution to this problem over the years ?

Have you found what it is that is causing this problem & what can stop it from happening ?

You have suggested buying a coated filter, but where are they available please ?

 

 

 

EDITOR'S NOTE: I don't think it is particularly Mr Uviroptics problem to solve. The problem belongs to all of us.

OXYGEN and MOISTURE cause the problem, as mentioned in *several* places. Let me remind you that it is your responsibility to inspect and maintain your filter set. And I also note that I have oxidized filters sold by other manufacturers. My Kolari had to be soaked in H₂O₂ last year.

 

 

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[enricosavazzi]

Replace the air with an oxygen free gas? Nitrogen would be ideal, but probably hard to do at home. It is a thing to fill your tires with nitrogen, because the nitrogen molecule is bigger and doesn't diffuse through the tire as easy as the oxygen in the air. Perhaps a box with a tire nipple on it where you could go to the tire store and get it filled with nitrogen. CO2 would be easy to get, but is probably too reactive to use.

I agree with other posters that this is probably the best alternative. I don't think this is particularly difficult. Just flood the bag with nitrogen before putting it in the sealing machine. Since air is mostly nitrogen anyway, in this way you can probably lower the oxygen content of the gas inside the bag by 90% or so.

 

I would be more concerned about evaporation/degassing of organic solvents and plasticizers from the plastic bag and any plastic containers used to contain the filters. In the long term, this may form deposits on optical surfaces. Before my last house move, for example, I had wrapped some lenses and microscope parts in cling film, anticipating that I would reopen the packages within a few weeks. I could do it only after about six months, and in most cases the cling film had left very visible deposits on optical surfaces (especially, but not only, those in direct contact with the plastic film). These deposits can be easily removed with lens cleaning solutions, but they are not what I would want on stored optics in the first place.

 

I don't know whether degassing can be a problem with silica gel. Perhaps a low pressure can force water vapor out of the silica gel?

[JMC]

I have a question (and Mods feel free to move this if you think it is inappropriate here).

 

Would putting the glass in a vacuum be expected to stop this phenomenon from happening?

 

The thinking behind this is based on surface energy. The surface composition of a material is different from its bulk. Also glasses will flow over time. Is it unreasonable to expect glass composition at the surface therefore to change over time, without the need for oxygen, contaminants etc etc? Could what we are seeing be driven in part at least by the glass itself?

 

Then, and rather worryingly, we clean the glass and remove some components from the surface, essentially creating a clean surface again. Chemical potential then tells us that components will move from areas of high concentration to low concentration, thereby driving the more mobile (or more easily washed off) components within the glass to the surface again.

 

Anyway, just a pre-coffee thought to start the day with.

[colinbm]

I was once told that the more energy put into making something, the faster it will try to return into its original form.

So are these glasses made from a mixture of oxides, that are easily oxidized ? I am no chemist.

[Nisei]

I like how they look in the bag, they make me hungry, the different colors must be different fruity flavors, but you would need a Fruitometer to know for sure.

:lol: :lol: :lol: :lol:

[colinbm]

It could be funny Nisei, but the reality is that this problem should have been addressed years ago & perhaps driven by the supplier going back along the supply chain & establishing the cause & solution. That is what quality control is about.

 

PS, Our domestic digital cameras use a similar glass to cut the unwanted UV & IR from our cameras, & we, as in this group, are all to keen to remove these UV/IR filters.

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

[JMC]

Colin, not heard that before, but normally some form of energy needs to be put into something to make it decompose or break down, a sort of activation energy. Of course some things will spontaneous decompose, or require only a small energy input to get them to break down. For example if you mix oil and water and shake it a lot (put lots of energy in) you'll get an emulsion typically with droplets of oil in the water. However the oil doesn't want to interact with the water, so the droplets of oil will coalesce very quickly, and you end up with a layer of oil and a layer of water. However if you add a surfactant and/or a thickener you can slow down this rate if coalescence. Skin creams are typically oil in water emulsions (a bit like mayonnaise) and when formulated correctly this mixture of oil droplets in water can last for years.

 

Anyway, I digress.

 

My understanding of glasses is at a really basic level. I believe they are a mixture of Si oxide, along with varying portions of other different metal oxides. The silicon oxide is a large polymeric type structure which provides the 'scaffold' to the glass, and the other oxides are present as either individual molecules or small clusters within that scaffold.

 

I'm sure some of the additional metal oxides can be further oxidised - a lot of metals can exist in different oxidation states - however whether this will happen spontaneously will depend on the energy required to make that change.

 

This is probably a very simplistic way to look at it and I'm sure there are plenty of other experts on here that can correct this if wrong.

[ulf]

I suspect the clinginess of cling-films are due to volatile plasticisers.

My unconfirmed feeling is that plastic bags made by polyeten intended for storing food in the freezer is a better alternative.

[colinbm]

Thanks Jonathan & Ulf

[JMC]

When I was working with Ultra High Vacuum systems we would wrap things in Al foil for storage to keep them clean. We never used plastic bags because of transfer of material from the plastic to the clean surface. However even with Al foil, it needed degreasing before it could be used.

[enricosavazzi]

I suspect the clinginess of cling-films are due to volatile plasticisers.

I agree, it fits my observations.

My unconfirmed feeling is that plastic bags made by polyeten intended for storing food in the freezer is a better alternative.

Partly true, I do not get deposits on optics stored in generic clean/unused PE ziploc bags. Plastic bags for freezer use, however, often feel suspiciously soft/rubbery/oily, unlike clean PE.