UV filters and humidity

[KaJashey]

I understand humidity is bad for a lot of UV filters. I took a break from photography and I come back and a lot of my equipments isn't in good order.

 

One thing that has problems is my UVIROptics La La U. It's got some fog on it. 

 

Is there an abrasive or something to get this off?

 

[lukaszgryglicki]

Mine AndreaU also starts to corrode :(. UVBPlus is OK.

 

[KaJashey]

I was hoping for a recommendation on what abrasive to use to remove the corrosion. Then I remembered I already had a set of silicon carbide powders.

 

About 30 minutes of dry polishing with a paper towel and 2000 grit silicon carbide the filter is mostly clear. Far edges are still a little cloudy but that doesn't matter to me. If I wanted to do a better job on the edges I'd probably have to remove the retaining ring.

 

The filter gets stored with desiccant for now. But first I'll take some photos.

[ulf]

Sorry for my late answer.

 

The typical polishing agent for glass-surfaces like uncoated filters is Cerium oxide. 

That is what is used in the optical industry to polish filter- and lens-surfaces.

 

There are different grades of cerium oxide and you should find a fine, high grade type.

It is normally used as a slurry, mixed with distilled water.

Sometimes it is sold like that.

I bought mine from my UVIROptics.

 

A quick search indicates that it can be found on both Amazon and eBay.

 

Only polish filters without AR coating with Cerium oxide!!! 

 

It is always a good idea to remove the filter round from the retaining ring.

Then the rear side can get good support during polishing.

For very thing filters there is a risk of cracking the glass.

 

All glass corrode over time due to humidity.

It is the same process that makes drinking glasses greyish if not used for a long time

Some filter glass materials are more reactive and corrode faster.

 

The IR-blocking S8612 from Schott is one of them and it is likely one component in your La La U.

 

Some of us have experimented with methods to decrease or eliminate that type of corrosion.

I think this works well, but as I live in a place with less humidity I am not that affected.

 

I have used Rain-X, normally intended for windshields on cars.

If I remember correctly Colin (colinbm) successfully tried a similar product.   

 

[OlDoinyo]

If you do not wish to use abrasive, soaking the filter overnight in a 5 per cent hydrogen peroxide solution also seems to remove this kind of efflorescence. But with a glued filter stack, the solution can sometimes get between layers which can be irksome.

 

[Doug A]

I feel so lucky to have a Schott S8612 with protective coatings. Worries me that it is almost irreplaceable. 

Thanks,

Doug A