Trying to Prevent Filter Glass Oxidation #1

[colinbm]

Repeated from "Sick S8612"

Thanks Andrea

Yes the consensus seems to be that it is oxidation, of what chemical composition ?

"Know thy enemy" seems to be the best defense, to win this battle.

We need to neutralize this enemy.

 

Yes I live in a hot humid area, but not as hot & humid as it can get, I only live halfway on the east coast of Australia, there is still plenty of country that gets hotter & more humid then here.

Moisture has been long branded as the culprit, but I have the filters with silica gel & the gel hasn't changed colour to tell me that it has finished absorbing the moisture....?

 

I am willing to donate my 'poxy' old BG39 filter & another older BG type filter for chemical analysis, if we have a chemist on board that is willing to look & sample these.

[dabateman]

Oh how quickly we forget.

Remember this thread:

https://www.ultravioletphotography.com/content/index.php/topic/3749-what-is-the-magical-ingredient-in-u340-to-block-ir-and-can-we-all-petition-hoya-or-schott-to-triple-it/

 

The most susceptible filters to degradation are U340, ug11, Ug5 and S8612.

Ug1 and U360 are not as sensitive.

 

Ug11 and ug5 are mostly phosphorus pentoxide, 60 to 70%.

 

Ug1 and U360 were mostly silica.

 

So the problem is phosphorus pentoxide, which is a very powerful binder to water. The glass surface is literally pulling water out of the air and forming acids which will etch and damage the glass.

 

Water is the problem, maybe not so much oxygen.

 

[Cadmium]

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.

 

I forgot to mention, Andy, Yucca Mountain, seriously great idea!

 

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.

 

Andrea, I have a lot of those I inherited from my dad. Some are blue glass, and some are clear, all sorts of shapes, sizes, and lids too.

Beautiful jars, I should use them for something, get them out on a shelf...

 

Here is an excerpt form a Schott catalogue.

---

After a certain amount of time, the surface of highly sensitive glasses exhibits a slightly cloudy residue. Initially, this residue can be removed using glass polishing compounds.

More severe attacks ruin the surface polish quality, however. This effect is caused by humidity.

---

Here are the glass types that Schott says are susceptible:

BG18, BG40, BG50, BG55, KG (all), BG42, UG5, UG11, BG39, S8612, S8022 and S8023.

However, I have seen small isolated cloudy spots on higher IR filters occasionally too, the black ones, so I would watch for those also.

I have never seen anything on colored longpass filters.

 

These two pdf links provide a lot of information about Schott glass, I suggest both are good reading:

 

https://www.us.schot...ies-2015-us.pdf

 

https://www.schott.c...on-2015-eng.pdf

[colinbm]

Oh how quickly we forget.

Remember this thread:

https://www.ultravio...t-to-triple-it/

 

The most susceptible filters to degradation are U340, ug11, Ug5 and S8612.

Ug1 and U360 are not as sensitive.

 

Ug11 and ug5 are mostly phosphorus pentoxide, 60 to 70%.

 

Ug1 and U360 were mostly silica.

 

So the problem is phosphorus pentoxide, which is a very powerful binder to water. The glass surface is literally pulling water out of the air and forming acids which will etch and damage the glass.

 

Water is the problem, maybe not so much oxygen.

 

Thanks very much Dave

So we need to bury out filters in Kitty Litter....?

OR find a clear UV passing sealer ?

[Cadmium]

Ug11 and ug5 are mostly phosphorus pentoxide, 60 to 70%.

 

Ug1 and U360 were mostly silica.

 

So the problem is phosphorus pentoxide, which is a very powerful binder to water. The glass surface is literally pulling water out of the air and forming acids which will etch and damage the glass.

 

Water is the problem, maybe not so much oxygen.

 

David, Indeed, phosphorus.

An excerpt from the S8612 Material Safety Data Sheet PDF:

--

 

https://www.schott.c...?tenant=ao-cert

[colinbm]

page 28

Chapter 7.2 Coatings

Polished filters can be supplied with additional optical coatings to improve the optical properties or add new functions to the optical filter component.Such coatings include:• Anti-reflection coatings• Protective coatings• Multi-layer interference coatings• Mirror coatings• Electrically conductive coatings• Demisting coatings (anti-fog/hydrophilic)

For more detailed information on coating capabilities,

please refer to our website www.schott.com/advanced_optics/optical-filter-glass or contact a sales representative. ** This link is dead.

 

Is there an option for coatings available to us Please ?

[dabateman]

Not kitty litter.

But an oil might not bee too crazy. For long time storage placing a filter in a mason jar of pure vegetable oil or olive oil may not be a bad idea.

 

Not sure which oil has the least amout of acid though. I would think an oil extremely low in acid content would be best.

 

Funny thing is that phosphorus pentoxide is better at pulling out water than silica drying packs. So if you want keep your drying packs dry, place them with a Ug5 or Ug11 filter. The filter will have higher water activity, causing the white acidic build up and preserve your drying pack.

[colinbm]

Well yes Dave that explains it pretty well.

All the silica gel packs with my filters are not showing any colour to indicate they have fully absorbed with moisture.

So we have been mislead all the time, all because there was no feed back down the Quality Control line.

It almost seems like these filters have built in obsolescence...!

Bravo to you Dave

The camera companies have done the right thing & coated their BG type filters, now we need the same or suitable solution....

[dabateman]

Companies don't like to share trade, Formula secrets.

Andrea looking to the MSDS's was brilliant.

 

If you like to mix and match glass for different colors effects, then nothing beats S8612.

If you want the best UV filter that will not go bad over 11 years stored open in a marsh land high 99% humidity. Than I can only recommend the Baader venus filter. I purchased mine in 2008, and its still excellent. The DC area including today is crazy humid.

[colinbm]

Yeah, thanks Dave, I was relying too much on the silica gel & like how they were packed & sent & I used some more silica gel to be sure, & as the silica gel didn't change colour like when it was finished I was assuming I was doing it right....but not.

Got to find a way to seal them without losing the properties.

But you would think it was in everybody's interest in the supply chain to make them serviceable & not dispensable, like this. I mean the camera companies are doing the right thing by coating them.

Anyway the problem is now known, as to why they are failing, now to protect them properly.

[colinbm]

So humidity is the problem, ie water vapour....I wonder if keeping the filter under water or Hydrogen Peroxide will be safe ?

Water & water vapour have different affinities ?

Hydrogen Peroxide maybe safe to Aluminium ? I know that brass is not, it reacts to give oxygen.

[Cadmium]

UPDATE: ITOS informed me that they do not carry S8612, a surprise to me. I got my KV-418 there, once upon a time. Not cheap, but good.

 

Coatings get complicated in the sense of quantity, and the glass needs to be lapped to the desired thickens first.

To get a more affordable price you need to make like 1,000 pieces, and it is still not cheap.

The other route to go is lap the glass as usual, then send those sheets to someone who specializes in coating glass, they send the glass back, and then you cut the circles or shapes.

Even more expensive, but lower required number of pieces, but still high, at least 5 to 7 sheets, sometimes more depending on the equipment used for coating.

So you are talking like 50+ 52mm filters. Doable, but complicated, and expensive.

That is why if you find some glass place that has S8612 and you want one or a few filters coated, they are not really set up for that,

because they would have to dedicate a large amount of glass to make one for more circles for you.

So please don't get upset about plain uncoated filters, just take care of them and they will last a long time with no problems.

If you let them go, without care, then expect the results of no maintenance.

[Stefano]

So humidity is the problem, ie water vapour....I wonder if keeping the filter under water or Hydrogen Peroxide will be safe ?

Water & water vapour have different affinities ?

Probably there is no chemical difference between water and water vapour. If something is attacked by water vapour, it will be attacked by water too.

[Cadmium]

See the thing is about S8612, it is better than BG39 for UV stacks. They both suppress high red and UV better than anything else per thickness.

You can use BG39 for UV stacking, but you will loose the 360nm peak amplitude, see in the graph of BG39 2mm vs S8612 2mm how the the 360nm point drops from 65% to 50%,

that makes a difference. For any situation where all you need is to cut red/IR off low, then BG39 will work for that, but keep in mind they both need maintenance examination and cleaning.

 

[Bill De Jager]

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.

 

Neutrino damage can be a real concern: https://what-if.xkcd.com/73/ I was hoping to get multispectral photos of a supernova in action from quite close up, but even with shielding that may not work quite as well as I had hoped.

 

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

 

YES !!! :lol:

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.

 

Yay, Spaceman Spiff! My favorite cartoon character of all time: https://calvinandhob.../Spaceman_Spiff

[Alaun]

What about sealing the filter surface with a wax polish?

[Andy Perrin]

We could remove the filter ring, put the filter in tissue paper between the pages of the family Bible or other holy book, and call it a day. No one will see that filter for 2 or 3 centuries. Tried and tested on letters and flowers.

[Nisei]

Probably there is no chemical difference between water and water vapour.

Yes there is: loads of oxygen.

[colinbm]

Reposted from 'Sick S8612"...

Manfrotto offer an affordable coating, 8 Layer Water Repellent Filter.......is this what we need for the BG filters ?

https://www.jbhifi.com.au/products/manfrotto-58mm-outdoor-uv-8-layer-water-repellent-filter

[SteveE]

There are nitrogen cartridges on Amazon, like the CO2 cartridges used to power paint ball guns, only filled with nitrogen. Apparently they are used somehow with food and beverages. Some are threaded and there are valves that screw on to threaded cartridges that are used to inflate tires. There is another dingus that looks like a small grease gun that is used to purge something in air conditioning. It has a trigger to release the gas and an attached hose. It should not be too hard to adapt one of these devices to fill a container. You would probably have to consume one cartridge per filling, but it shouldn't be too cumbersome an operation.

 

WARNING: compressed gas cartridges are dangerous. ONLY use an appropriate commercially made device for releasing the gas. If an opened one gets loose, it will be propelled by the escaping gas like a bullet, and like a bullet, it can kill. Use at your own risk. You assume any and all liability for any use of these cartridges or devices.

[colinbm]

The discussion has moved on from using gases.

You will need to read some of yesterdays (my time) later posts & you will see that it is a chemical reaction with water vapour ie humidity, that is causing the problem.

Removing or preventing contact with this humidity / water vapour is still the problem to be solved.

[ulf]

The discussion has moved on from using gases.

No it has not.

Using gasses is probably still the best practical alternative for protecting filters without cladding or coating, like the excellently custom crafted filters from UVIROptics.

By purging the air with something non reactive you will prevent contact with humidity / water vapour.

 

You now are demanding alternative processes to add to the process of grinding, polishing and cutting the filter glass discs to add additional protection from humidity.

Big professional companies like Schott can do such additional steps if you are willing to pay for it, but for such low volumes like the needs for our community they are completely out of reach.

Just to start making filters like that there will be a minimum order quantity to at all be accepted.

 

Normally they are expensive industrial batch processes and you would have to pay for a big batch of filters with such treatment.

The equipment for such processes are an expensive investment.

 

There might be other ways of protecting filters beside cladding or coating, but it is a bit unlikely this could be done on a single filter basis to a reasonable cost.

[colinbm]

Thanks Ulf

Gases are an option, but I am not sure how dry of water vapour they are ?

[ulf]

Compressed air from a compressor contain water vapour, but quality gasses not so much.

 

If you get quality Argon 99.998%, High Purity 4.8, there is not much space left for water.

That is the reason for me to push for argon. That quality is used for some types of protective gas welding (MIG).

[colinbm]

Thanks Ulf, yes, but, Dave showed us yesterday that the BG glass filters are a big sucker of moisture & it will out-suck silica gel by miles....
So if there is a minute bit of moisture it will go straight into the BG glass & do its dirty work.