Cleaning a Filter

[skir]

I've managed to get a slight finger print on a uhc filter (slipped from my hand whilst mounting it). Is it worth trying to clean it and if so what would be best to use and any particular techniques to best complete the task?

Sent from my Nexus 7 using Tapatalk 2

[NGC 1502]

Yes, I've done that too, but a finger print is better than dropping it

After carefully flicking off any grit, I put a small amount of isopropyl alcohol on a folded micro fibre cloth, and very gently wiped the filter. It took a couple of tries to do a streak free job.

Maybe the popular Baader cleaning fluid would be good as well ?

Regards, Ed.

[Carbon Brush]

Having wrecked the coating on spectacle lenses using IPA, I avoid it on optical glass.

Yet to see a problem resulting from the Baader fluid.

[NGC 1502]

Having wrecked the coating on spectacle lenses using IPA, I avoid it on optical glass.

Yet to see a problem resulting from the Baader fluid.

Hi David, I'm sorry if your specs were damaged by using IPA ( I'm assuming that's isopropyl alcohol), but I've never had a problem.

Maybe there was some other reason the specs were damaged ?

Here's a link from TeleVue on optical cleaning http://www.televue.com/engine/TV3b_page.asp?id=103

Of course, cleaning too often, or aggressively, is not a good idea (not saying that's why the specs were damaged)

All the best, Ed.

[Carbon Brush]

Hi Ed. Yes isopropanol was definitely the culprit.

This was the decent high purity stuff and always evaporated from other things without leaving a film.

I used IPA repeatedly to clean specs. It being very good for removing finger/skin grease, etc. After (probably) 20 or 30 cleans, I started to notice a bit of coating coming away from one lens. Gradually this worsened. The remaining coating could be flaked off easily using a fingernail. A work colleague suffered the same problem.

Both sets of specs were bought from specsavers at different times, so it couldn't be put down to one of us mistreating the lenses, or a bad batch. It was definitely that the coatings would not stand this solvent.

Another time I wrecked a pair of specs lens coatings by heat. I left them in their case on a black dashboard for about 3 days in nice weather. When I came back, the coatings looked like broken safety glass, loads of little pieces. As they were only a few months old, I got them swapped out in guarantee. That was D&A. Beware leaving scope stuff in a car?

I have since asked opticians about maximum temperature before lens coating damage. They had no definite answers. Run under a hot tap? Should be OK. So I put it to them that I could pour boiling water over the (metal frame) specs to get the lenses clean. Not sure was the reply. Leave them in a car on a sunny day? Definitely OK they said.

Now specs lenses are plastic, not glass. I'm reasonably sure the coatings and/or the application method are different to glass coatings because of temperature restrictions. But I still don't take chances on scope stuff. Any stuck dirt, grease, etc is removed using Baader wonder fluid. OK a tenner for a small bottle sounds a lot. But against £100 for a decent eyepiece? Or a scrap Mak due to wrecking coatings on a corrector plate? Or a wrecked refractor objective?

Perhaps Baader fluid is simply distilled water, IPA and drop of mild detergent to discourage droplets? Perhaps I could make this myself much cheaper? I don't know and given that one bottle looks like lasting several years, I'm not going to take the risk on my decent kit.

Perhaps one day I might experiment with chemically wrecking coatings on something that has been scrapped for other reasons.

[skir]

I think I'll have a go at the baader fluid just to be on the safe side, thanks for your advice.

Sent from my Nexus 7 using Tapatalk 2

[NGC 1502]

Hi David, thanks for going to the trouble to post that info.

Food for thought indeed, and yes the Baader fluid sounds the safe bet.

Regards, Ed.

[glowjet]

I believe I have read that Baader filters are manufactured with a hard coating finish to enable them to be cleaned, of course, they recommend their own cleaning fluid and cloth, which is no doubt used by a good many of the forum members, but a simple clean with distilled water and a smidgen of washing up liquid on cotton buds and a final polish with a micro fibre cloth may do no harm, so long as any grit particles have been removed by a blower brush first. However, investing in the Wonder cleaning kit could be the best way to go in the long run

John.

[Carbon Brush]

I'm sure that coated glass is generally much hardier than coated plastic.

But in these days of subcontracting, can you be sure of consistency?

The quality optical manfufacturer may know he has good product that can be (almost) cleaned with sandpaper when he makes his own filter.

But if he subcontracts, or outsources any parts, can he still be certain?

Can we be sure that the kit bought 5 years back has the same 'recipe' as today's kit?

Even the big boys get caught out here sometimes.

Remember the rusty Meade PST objectives?

On the same lines, but different, if you get my drift.

A few years back there was a spate of laptops catching fire due to battery failure. Don't get the lawyers on to me if I'm wrong, but I think Sony/HP/Compaq were involved. The grey cells aren't what they used to be!

Basically the Japan based battery designer/manufacturer was subcontracting battery pack assembly to China. Someone there used the wrong type of cardboard separators between cells and some failed giving short circuits, resulting in fire.