Cleaning solar filter

[KenG]

I had some internal work done to my house recently and when I went to use my solar filter yesterday - yes, the sun was shining! - I discovered the lid of it's box was detached and there was a layer of fine dust - a mix of sawdust and plaster - on the glass. I blew most of it off with an air brush but a residue remains and I don't want to touch it without some advice. It's the outer face i.e. the one facing towards the sun that's affected. How should I go about cleaning off the remainder? 

[Uplooker]

Use it - it will make no diffrence, jus don't rub the filter, with anything. Why not just run it under the tap, let it dry naturally.

[Peter Drew]

Glass filters are usually coated with inconel which is pretty tough. Do as Ian suggests in the first instance and then see if it needs further attention. Don't try this with solar film. 

[KenG]

Thanks for that information. I tried water as you suggested but it made no difference, however, I then read up on Inconel, which it turns out, is indeed tough - in fact it's described as being very resistant to damage - and applied to only one surface of the glass, which is important. Having examined the filter, it's quite obvious that the coating is applied to the inside face i.e. the one facing the telescope and on my filter it's the outer face that needs cleaned, so looks like I can safely remove the remaining dust using optical cleaning materials.

[Joe12345]

I had some solar filter which I got glue on. I washed it under a tap and scrubbed it with my nails and toilet paper. Then I dried it roughly with a towel. Perhaps not the safest way, but it still works!

I'm not suggesting you try this though, seeing as everyone says to treat it with care!

[KenG]

Well, for the information of anyone reading this, I used a glasses cleaning spray to put a light coating on the outer face of the filter and then gently removed it with a lens cleaning cloth and I got a perfect result. It's important of course to ascertain from the outset which face is coated with Inconel. I wouldn't attempt this on the protective film itself.