A Blue 'Mist' on the Mirror of my Newt...?

[Dave In Vermont]

I had the mirrors on my 200mm F/4 Newtonian re-mirrored about 2 years ago. And have now removed the secondary to fit a new focuser. And I just noticed strange blue-ish areas on the secondary. They seem to have clear 'ravines' running through these misted areas - like water had been running in tiny rivers through the misted areas (no water has been anywhere near - mirror has been resting covered). So parts of the secondary are nice & shiny and perfect, while others are in a blue mist.

So much for trying to define this oddity with linguistics - try some photos.....

 

          

 

Anyone have any ideas on what this is all about? I've never encountered such before.

Weird -

Dave

[bottletopburly]

Had something similar caused by diesel fumes from a cement mixer when I done my patio , cleaned it still couldn't budge finally used  neat white vinegar dampened on a very soft microfibre and lightly dragged over surface , drastic I know did the trick ,then rewashed mirror 

[alacant]

2 hours ago, bottletopburly said:

caused by diesel fumes

I had something almost matching this description when dew formed from polluted air which I traced to smoke from a bbq; the water then evaporates leaving the solids from the smoke particles forming a film. I'd guess the ravines are where the condensation has coalesced into droplets and run under gravity. I removed it with one of the cloths used to clean spectacles. HTH.

[Peter Drew]

I wouldn't do anything drastic as a first attempt to clean it. Try some warm water with a drop of washing up liquid applied to the surface with just the weight of a cooton wool ball soaked in the water.  

[Commanderfish]

I was going to ask, is the scope stored in a garage?  Looks like a layer of petrol, diesel or maybe butane or propane fume condensate.  

Given that such chemicals might eat at coatings, I'd wash with filtered (or better yet distilled) water.  I cleaned the primary of my 10" with filtered water and dragged some cotton wool across it very gently, came out mint with zero damage.  

Considering that it looks like water condensation has wiped some of this stuff clean already, I think it might come out perfect by just pouring over some filtered water.

[Dave In Vermont]

It was stored indoors - under a sheet of plastic-wrap (Hmmm...) - nowhere near auto exhaust or other petro-sources. I'm wondering if the plastic-wrap could have transfered onto the mirror?

Curious. If it did - then what's it doing to the food it's supposed to be used to wrap?! This should keep me busy for awhile.

I'll get some distilled H2O and have-at with some surgical-grade cotton-swabs.

Dave

[Commanderfish]

Excellent questions...  I just used a drinking water filter, seemed to remove all the limescale rather well.  Distilled is better of course - though no idea where I would buy any...

 

[Dave In Vermont]

1 hour ago, Commanderfish said:

Excellent questions...  I just used a drinking water filter, seemed to remove all the limescale rather well.  Distilled is better of course - though no idea where I would buy any...

 

Over here, distilled H2O is available at 'Drug Stores' - which I think you call a 'Chemist.' Make a few calls?

Dave

[alanjgreen]

1 hour ago, Commanderfish said:

Excellent questions...  I just used a drinking water filter, seemed to remove all the limescale rather well.  Distilled is better of course - though no idea where I would buy any...

 

You can use de-ionised "battery topup" water from Halfords. Its purer than distilled and is great for rinsing mirrors with no residue

http://www.halfords.com/workshop-tools/garage-equipment/battery-chargers-jump-starters/halfords-battery-top-up-water-5l

[Dave In Vermont]

De-ionized is purer than distilled? I don't think so.

I'm an organic-chemist. The process of distillation involved boiling the water into a vapor and allowing it to travel over & through a condenser that has a cold-liquid running through an outer jacket to facilitate the vaporized water to condense back to a liquid. This is usually done 3X to ensure that all that you end up with is ultra-pure water.

De-ionizing means you simply react any possible positive or negative charged ions to a neutral-state that won't react to cause an electric-charge - or detract from one either. But it may still leave residual materials behind following evaporation. Distilled-water leaves nothing behind.

Dave

[Astrobits]

If your plastic food wrap is based on PVC then it is full of plasticisers which will leach out. These make the plastic flexible and tacky. Just Google  "PVC plasticisers" to get some of them, mainly long chain phthalates. If that is the case then water will not clean your mirror and you will have to try other, more vigorous, materials. I would start with soap solutions and if that doesn't do it then some commercial lens cleaner or organic solvent such as Isopropyl Alcohol. ( nearly used the abbreviation IPA there but here in the U.K. that is a beer and while it may wash a mirror it is much better being drunk)

Nigel---hic!

[Dave In Vermont]

Thank you Nigel!

I was rather thinking along similar lines. I've got some 91% iso-Propanol (IPA) on hand. And Dawn for dishwashing - same brand used on Seabirds that meet with oil-leaking wrecks. But that'll have to wait until July 5th - when I'll have my next occasion to pick up some distilled H2O in town.

Here in ULTRA-GREEN Vermont, I'll enjoy writing an article for our local paper on what is out-gassing from the plastic food-wrap! I can see the prices on the stock-market plummeting now!

Woof!

Dave

[Stu]

54 minutes ago, Dave In Vermont said:

I'm an organic-chemist

Crikey Dave, I thought you were a bike mechanic?

I use RO (reverse osmosis) water from an aquarium. Very cheap and works perfectly, no residue at all.

[Astrobits]

There has been a lot of concern for many tears about the plasticisers from cling film entering the food chain. Steak and Phthalates anyone?

Nigel

[Stargazer McCabe]

To you gentlemen like @Astrobits; would such plasticisers be present on weather resistant polyethylene barbecue cover ? A friend I visited this weekend has a SkyWatcher FlexTube stored inside his house, under one of these to keep dust off. I believe he has several 100g Silica Gel packets under to cover to thwart condensation. 

Could the same issue be encountered ? If so I'll give him a buzz...

Ed

[Dave In Vermont]

If it truly is polyethylene - it shouldn't be. But unless it swears up, down, and sideways it's straight-up polyethylene...? Who knows?

Over here, plastic-containers "should" have a triangle-imprint in the base of the thing with a number indicating what plastic it actually is. I don't know what the regulations are in the UK (but I'd like to!). Non-food items have more lax regulations over here - but I'm now betting that plastic-wraps are in some obtuse catagory that can slip through the cracks.

For myself - I think I'll just be avoiding 'plastics' whenever possible!

Nigel? What say thou?

Stu - I AM a bike-mechanic. AND an organic-chemist. And many other hats I have, too. Woof!

evaD

[barkis]

Maybe your Aluminiser  used Magnesium Fluoride on your mirrors, and some catalyst has caused it to react.
That substance is used in optics.

[Dave In Vermont]

5 minutes ago, barkis said:

Maybe your Aluminiser  used Magnesium Fluoride on your mirrors, and some catalyst has caused it to react.
That substance is used in optics.

MgF2, and other fluorides of similar nature, require some pretty strong acids to get it to react - especially in a way to release HF (hydrogen fluoride) that can etch glass. But I ran that through the proverbial mill, too.

Dave

[westmarch]

On 27/06/2017 at 05:42, Dave In Vermont said:

I had the mirrors on my 200mm F/4 Newtonian re-mirrored about 2 years ago. And have now removed the secondary to fit a new focuser. And I just noticed strange blue-ish areas on the secondary. They seem to have clear 'ravines' running through these misted areas - like water had been running in tiny rivers through the misted areas (no water has been anywhere near - mirror has been resting covered). So parts of the secondary are nice & shiny and perfect, while others are in a blue mist.

So much for trying to define this oddity with linguistics - try some photos.....

 

          

 

Anyone have any ideas on what this is all about? I've never encountered such before.

Weird -

Dave

Dave,

your laptop screen looks like it is going the same way.  Is there a common factor? 

John

[Astrobits]

Ed:

Polythene ( polyethylene) is a naturally flexible polymer so no plasticisers are needed. However, as the B-BQ cover is made for outside use it almost certainly has other ingredients such as UV stabilizers and, presumably, pigments that do have the potential to bleed to the surface. They are not as volatile as the plasticisers used in PVC so as long as the cover is not touching any delicate optical bits it should be O.K.

PVC in it's 'natural' form is very rigid, think rainwater goods like guttering, and needs plasticisers to make it flexible.

Dave:

Yes we also have the triangular identifiers but these only appear on containers, things like polythene sheeting and cling film don't get the mark. The marks are primarily to aid recycling as mixing plastics is not a good idea if you want a usable product out of the end. For example, Polystyrene and Perspex (aka Plexiglass ) are both clear rigid plastics in their natural state but they do not blend together, they are, like oil and water, not miscible.

By the way, Ammonium Fluoride is used to etch glass as well as HF. It is at least less volatile although still pretty dangerous if not handled properly. When I had an old enamel bath re-coated with a polymer the operators used it to etch the enamel ( =glass) coating so that the bonding was as good as possible.

Nigel

[Stub Mandrel]

That doesn't look good, I hope you get it sorted. I always thought it was the 'red mist' that caused problems!

I've used 'armor etch' to remove degraded coating from spectacles to get them another year or two's life! It removes the mineral coating and leaves the plastic behind, it's flouride based.

Nasty, but HF is really nasty.

 

[Stargazer McCabe]

@Astrobits

Nigel, thanks for the comprehensive reply. I'll print off this thread in readiness for the next time I see him. Not 100% certain of what the cover was. But your advice is useful I'm sure and maybe it'll be better to be safer than sorry... Anyway, whatever he decides to do; I'll have done my bit 

[AdeKing]

1 hour ago, Stub Mandrel said:

That doesn't look good, I hope you get it sorted. I always thought it was the 'red mist' that caused problems!

I've used 'armor etch' to remove degraded coating from spectacles to get them another year or two's life! It removes the mineral coating and leaves the plastic behind, it's flouride based.

Nasty, but HF is really nasty.

 

@Stub Mandrel I agree, HF is a horrible substance I spent four years doing a PhD and using it to dissolve silicates from rock samples to recover fossil pollen.

Glad I don't have to do that anymore.

[Dave In Vermont]

6 hours ago, westmarch said:

Dave,

your laptop screen looks like it is going the same way.  Is there a common factor? 

John

No, the laptop-screen is just moved around in & outdoors. And they're of different materials anyway - plastic rather than glass and a mirrored surface. I just wipe it down with a damp sponge when it annoys me enough.

The affected secondary was wrapped in the plastic-wrap and was airtight. And that's what I'll wager was behind this situation. The primary mirror to the scope is fine - with no plastic-wrap on that. Which drives another nail into the coffin of the plastic-wrap.

I'm looking foreward to finding what solvent will remove the 'blue-mist.' That will tell me volumes to finding out the chemical composition of this 'mist.' Knowing Vermont as I do, there's a very good chance that Vermont will ban this variety of plastic-wrap for any food-storage applications. And well they should!

Ban the Wrap!

Dave

[knobby]

Whatever you try, try it on the edge first... At least just the edge will be damaged if it goes wrong .

And good luck.