Isopropyl Alcohol as a lens/mirror cleaner or dissolver of optical coatings

[pmrid]

What are your thoughts about this. I was about to embark upon a morning chore of removing the dust motes and other bits of whatever that seems to end up on glass surfaces and imaging chips. I'd seen somewhere in these forums a reference to isoptopyl alcohol as the cleaner of choice for this sort of job. The only form of this stuff my chemist could supply was a 65% solution (it didn't say what the other 35% was) under the brand name isocol. I wasn't entirely comfiortable - not knowing what that other 35% was and being concerned about the effect of this stuff on coated optics.

So I dragged out a couple of old/cheap eyepieces and used them as a test.

When I had smeared some of this across the surface of a coated eyepiece with a bit of cotton wool, I had a look at that surface under a magnifying glass: it seemed to me that the alcohol had dissolved/melted the coating. That was the end of that experiment and the beginning of this thread. Before I go any further with the CCD's can you tell me what you use for cleaning glass elements in your imaging train, and CCDs in particular.

Peter.

[allan gould]

70% isopropanol - 30%double distilled water.
Nothing else.
You may have just partially removed years of grease build up from eyelashes rather than any coating.

[Dennis]

Some time ago I purchased some 99% IPA from the Chemist – I had to show him my book on cleaning optics before he would sell it to me, for fear of misuse.

I think that anything less than 99% proof “may” be contaminated with other additives. IIRC, one post on sci.astro mentioned that some sort of oil was added to cheaper solutions and this would leave a film after the alcohol had evaporated.

The above comments are made up mostly of memory recollections and is not qualified advice, just a warning to check!

Cheers

Dennis

[dannat]

some isopropyl alcohol sold in chemist/pharmacy os really mouth wash & can have additives. Luckily i work in school & know i am using 99% proof watered with distilled - this liquid combo should be safe to use on all optical surfaces.
A chemical company can sell you the good stuff so to speak
Sometimes acetone (nail polish remover) is a stronger solvent - (we used to use it to remove urine from our microscopes)but it is possible it could damage/degrade some coatings or plastic parts near glass surfaces. Always wash it well off with water.

[pmrid]

Daniel. I am absolutely not going to ask about the microscopes... Honest, I'm not. No, really!!!
Peter

[marki]

Bunnings paint section: diggers isopropyl alcohol @ 100%. Its an easy and cheap alcohol to distil so I don't doubt it. Comes in a spray bottle to boot. I usually dilute it to 70:30 using de-ionised water and it works a treat. I also have and tried the very high analytical grades of isopropyl alcohol (2-propanol) at work and the diggers version does exactly the same job. Will not affect UHTC coatings on meade optics. Low grades will have impurties such as 1-propanol and water left from production.

Mark

[Hagar]

Peter, I would ask the Chemist to order in the 99% for you. It is not cheap, from memory $35 for 0.5 L but it is the good stuff. It is available but usually only by order.

[Tandum]

I got hold of some diggers isopropyl alcohol from bunnings tonight and sprayed it on plastic and then hit it with a hair dryer and it completely evaporated, quick smart. I did the same with some isocol and was left with lots of water droplets after hitting it with the hair dryer. It looks like diggers will do it, $11.70 for 125ml.

[AlexN]

I don't know if I'd use Isopropyl on optics... I definitely think its great for cleaning camera sensors, but I would be wary of touching mirrors or APO telescope lenses with it... tiny dust spots on a telescope lens will go unnoticed in both visual and photographic use, and by cleaning it all you are doing is risking the optical integrity of the telescope... most of the dust motes you see in images will be dust or specs of something on the sensor or on the filters, and its usually fairly easy to tell which is which based on the intensity of the mote in a flat frame. With your QHY8, its easy enough to open the camera up, clean the sensor and the optical window then seal it back up, and I think thats worth doing (I used to do mine once a month)

On the Astro-Physics website, Roland has a bit of an article covering his thoughts on cleaning refractor lenses.. Summarized, he basically says that until you notice it visually, do not touch it. and once you do notice it, get it professionally cleaned by someone who knows what they are doing..

[marki]

Not sure about your scope optics Alex but it is the only cleaner recommended by meade for their UHTC coatings. Robin it doesnt hurt to dilute the alcohol with some deionised water. Cleans well and leaves no marks.

Mark

[Andrew C]

I have a sense that isopropyl alcohol reacts with aluminium, so would be wary about using it for mirror cleaning. There is some chemistry here that I don't understand, but when I used it once I was convinced that it left streaks that did not dissolve in distilled water.

Would be interested to hear from a chemist on this.

[marki]

You will have to let me have a think about that one as it is a secondary alcohol which are not that reactive to start with (could be wrong will check). In any case I would not be using anything but de-ionised water and mild detergent to clean your mirror.

Mark

[marki]

Update from the MSDS datasheet. Seems your hunch is correct.

10. Stability and Reactivity
Stability:
Stable under ordinary conditions of use and storage. Heat and sunlight can contribute to instability.
Hazardous Decomposition Products:
Carbon dioxide and carbon monoxide may form when heated to decomposition.
Hazardous Polymerization:
Will not occur.
Incompatibilities:
Heat, flame, strong oxidizers, acetaldehyde, acids, chlorine, ethylene oxide, hydrogen-palladium combination, hydrogen peroxide-sulfuric acid combination, potassium tert-butoxide, hypochlorous acid, isocyanates, nitroform, phosgene, aluminum, oleum and perchloric acid.
Conditions to Avoid:
Heat, flames, ignition sources and incompatibles.

Appears it does the same as a primary alcohol with sodium metal and forms a Al salt (aluminium isopropoxide). The hydrogen is knocked of the hydroxy group and forms hydrogen gas, The Al dissolves forms a salt.

Mark

[DavidU]

Yes, a similar problem to Aluminium car engine parts and Ethanol fuels.

[allan gould]

Highly unlikely, there was probably some impurity in the alcohol used. Isopropanol will evaporate with no residue. Remember your coating is NOT aluminium but aluminium oxide, an enert unreactive matrial. Powdered aluminium or even metalic is different.

[marki]

Allan, I very much doubt the mirror has an AlO3 coating. MgF2 or SiO2 yes.

Mark

[allan gould]

Still the point is, neither/none of them is Aluminium.
We use isopropanol every day and reactivity with Aluminium is not one of our concerns.

[casstony]

I've used Isopropyl for years without any damage to lens coatings; on occasions I also use Acetone to remove stubborn deposits that aren't removed by Isopropyl (need to not let acetone touch anything other than the glass). It's better to disolve a deposit with acetone than to rub hard with Isopropyl.

Eyelash oil on eyepieces should be removed as soon as possible. Objective lenses that get dewed should be cleaned occasionally since contaminants in the atmosphere damage coatings. All IMHO.

[multiweb]

Just a thought [Satchmo] would know that. He's a mirror maker. Hear it from the horse's mouth. :thumbsup:

[rat156]

Actually raw Aluminium converts to the oxide faster than you can blink. The surface of almost all aluminium is coated in the oxide as soon as it's exposed to air. So it is possible that it is coated in Al oxide. Some mirror manufacturers coat with SiO2 after the deposition which is done in an atmosphere devoid of oxygen (and all other gasses). Most don't though.

Cheers
Stuart

[marki]

Yes but the Al coating is applied in a vacuum so oxidation will not be a major problem particularly if the protective coating was also applied before the mirror was exposed to air. My concern is simply based on the integrity of the protective coating considering their micron thickness. Mirrors that are exposed to the environment such as the case in open tube and truss frame designs have to have their mirrors recoated periodically as the Al coating some how comes in contact with oxygen (eg the coatings fail) and dulls due to oxidation and the formation of AlO3. Could it not then be possible that 2-propanol used as a cleaner might also reach the surface Al ? I imagine any scope mirror that did not have protection against oxidation would have very little usefulness beyond 48Hrs as the mirrors would dull rapidly. Just as an aside, I did a little experiment today. Freshly cut Al does indeed react with with 2-propanol but very very slowly. It took about ten minutes for the surface to visibly dull.

Mark

[RobF]

All this talk of chemistry and labs stimulated my safety gene. Be careful with isopropanol:

- extremely flammable
- nasty in your eyes
- don't want to breathing it in too much while you're agonising over your optics

Probably why the chemist was worried about selling. Really just requires the care and respect you'd give while using any solvent.

Safety rant over now.... :rolleyes:

[rat156]

I doubt that it was the IPA dulling your Aluminium. Freshly cut Sodium reacts slowly with IPA, that's what we use to get rid of excess Sodium without too much of an exotherm. Probably dissolved Oxygen in the solvent. AlOxide coatings on fresh aluminium are essentially impervious to liquids, though gas molecules are small enough to permeate slowly. Alkaline or acidic solutions will slowly dissolve the AlOxide and dull the Aluminium surface, which is why you shouldn't leave your mirrors wet. Also remember that most aluminium available to us is an alloy, not pure aluminium as would be vacuum deposited.



Geez, I'd hate to take you to a petrol station...

Petrol
- extremely flammable, forms explosive mixtures with air readily
- nasty in your eyes, on your skin (especially in those sensitive areas)
- don't want to breath in too much
- until recently actually contained a heavy metal poison (Lead)
- until recently contained a confirmed carcinogen (benzene)
- contains CNS toxins (Xylene and Toluene)

Amounts in use, IPA about 125 ml, Petrol usually over 40 litres...

Cheers
Stuart

[Bassnut]

How about Windex?. I tried it once, and it gave a very clean, streak free finish, better than anything else I have tried. Worried me a bit though, there is no mention of chemicals used, but the instructions say dont use on acrylic,fiberglass,painted surfaces, waxed, polished or varnished wood, or tinted windows. What do you think would be in it?, would it damage Al coatings?.

[rat156]

From memory the windex formulation had ammonia in it, avoid it for that reason alone.

Cheers
Stuart

[coldspace]

Tks Mark, good ol Bunnings.
I have been using the Bintel fluid and its OK, but I still used pure Iso that I had from an Orion optic cleaning kit and this does the job superb but I ran out last time I cleaned my corrector. BTW the Meade site recommends at least 90% or better Iso so diggers at 100% makes me feel better. I will pick up some next time I am at Bunnings.
Here's the link if anyones interested.
http://www.meade.com/manuals/lx200/apxe.html

Matt.

[marki]

Stuart both were analytical grades (eg pure Al we use for experiments not an alloy). Like you we also get rid of excess Na metal in 2-propanol for the same reasons and yes the reaction is very slow. I cleaned the Al surface with emery then steelwool and plunged it straight into the alcohol. The sheen of the Al dulled mildly after about 10 mins. Obviously acid or hydroxide will damage the coating with ease (the hydroxide will etch the glass of the mirror as well if it is of a high enough molarity) so best to keep these well away. As for the mirror coating being AlO3 I am unsure. From what I have read on mirror coating it is only possible to achieve the quality required in a vacuum chamber which is evacuated then the Al atomised to form the coat. In any case I would not put alcohols near the mirror sticking to de-ionised water and a mild detergent in the worst cases. Like you my initial thought on this was the 2-propanol must have been contaminated but I am not so sure after mucking around today. I am not excluding dissolved oxygen but I have never seen this happen using good old detergent and de-ionised water and think it's better to be safe then sorry.

Mark

[marki]

Fred I would not put windex anywhere near your mirror. It often has impurities that cause streaking. You can filter these out some what through high grade filter paper but still.... Ammonia in water forms hydroxide and this can attack the ali and etch the glass. It will only be about 3% ammonia but still not necessary when detergent and de-ionised water can do the job without risk.

Mark

[RobF]

Maybe I should switch to selling petrol. Gov safety regs now force we lab rats to have to read and signed off on MSDSs for up to 100 substances a year. Sniffing petrol might be easier......:rofl:

[marki]

I have to read the MSDS sheets and a danger report prepared by the lab tech then sign off for each bloody experiment we do in class. Lets see, 2 x year 12 chem classes, 2 x year 11 chem classes then there's years 8 - 10 AAAAAARRRRRRGGGGGGHHHHH. The poor tech is pulling her hair out. She has spent most of the year preparing the reports :D. We were using toluene, cyclohexene and cyclohexane as well as bromine water today (fresh and fumming, I tell the kids it will kill thier libido, they don't want to go near it) . This was the first organics lab with my 11's. Even though most work was done in the fume hood there was a lot of broken glassware and several stoned kids:rofl:. Some of my brightest and most responsible students regressed to the kindy sandpit:P.


Mark

[rat156]

Some phrases from the MSDS of the things I work with on a daily basis...



Extremely hazardous material. Known human carcinogen. May be fatal if inhaled, swallowed or absorbed through the skin. Causes severe burns. May cause serious eye and lung damage.
Toxicity data
ORL-RAT LD50 2.4 mg kg-1
ORL-MUS LD50 8.1 mg kg-1
SKN-RAT LD50 1.7 mg kg-1
Highly toxic if swallowed, inhaled or absorbed through the skin. Exposure to even small amounts may be fatal. Readily absorbed through the skin.



Vapor (Inhalation/Ocular)
ECt50 (Mild) = 0.1 mg-min/m3
ECt50 (Severe) 2 = 10 mg-min/m3
LCt50 = 15 mg-min/m3
Vapor (Percutaneous)
ECt50 (Threshold) 5 = 10 mg-min/m3
ECt50 (Severe) 2 = 25 mg-min/m3
Liquid (Percutaneous)
ED50 = 2 mg/70 kg man
LD50 = 5 mg/70 kg man
LCt50 = 150 mg-min/m3

We don't have broken glassware. You want to see the risk assessments...

Cheers
Stuart

[marki]

Been there, done that, chickened out coz I like living :P. Can send you some students to test some of those chemicals on if you ever doubt the validity of the MSDS sheets :).

Mark

[rat156]

Already been tested on humans by the Germans and Iraqis :(:(:(

[Satchmo]

Isopropyl is a standard for removing greasy deposits on aluminium /overcoated coatings and antireflective thin film coatings. I've found the usual routine of cleaning first with wads of cotton wool and warm dilute water before distilled rinse, isn't enough to get rid of a very tenacious greasy layer on mirrors cuased my air pollution and Eucalyptus oil if you live near the bush, so isopropyl is needed.

The standard test for cleanliness of an aluminium coating is to breathe on it and look out the breath pattern . If it is featurless and even then the coating is clean. if it is spotty and blotchy with big dark spheres then you have an oily deposit. I find that with a clean mirror displaying some greasy deposit even after a standard clean and isoproply , that a buffing with cotton wool and just the moisture of solid breath gives enough action to lift it. There is no danger of scratching the overcoat ( which is as hard as glass) so long as your materials are clean, and only a contamination that is Silica like will be hard enough to cause scratches.

I disagree with one poster that many modern optics are not over-coated. Unprotected aluminum surfaces will look noticeably dull after 6 months of oxidisation and do not cut it in the commercial world. I would say that uncoated surfaces these days would be extremely rare, although there is one aluminisation service in Australia that does not do it.

[multiweb]

Hi Mark, is acetone ok as well?

[Dennis]

Hi Marc

I have read that acetone can attack (melt!) certain plastics so if this is the case, I’d be very wary about using it!

Cheers

Dennis

[multiweb]

Sure does but I found it very effective at spot drying (water marks) on mirrors with coton.

[DavidU]

I used to use Acetone to clean acrylic sign panels. I have also cleaned a Achromat doublet with it. I had a web page with instructions I found.(Analytical scientific LTD)
BEWARE ! as Mark said it can dissolve some plastics.
http://www.analyticalsci.com/Astronomy/Telescopes/imagestv/cleaning_eyepiece_and_telescope_.ht m

[multiweb]

no worries - thanks for the tips.

[marki]

Marc acetone (propanone) should be OK. It is a good solvent and cleans well. It should not affect the Al mirror surface or the glass but I would check on the coatings. I suspect these would be reasonably inert in any case. As has been mentioned it can dissolve some types of plastics so contact should be avoided. I wonder how diethyl ether would go? Might try that out on an old mirror.

Mark

[MJ_]

Hey guys im a chemist and use solvents all day at work. I can tell you from my experience isopropanol is great for cleaning glass. Dont waste your money buying the expensive stuff from your pharmacy, goto bunnings and get the Diggers brand, it will be in the paint section with all the other solvents. It has no other additives and its purity is fine for use as a cleaning agent.

Isopropanol is flammable like all other solvents, just dont smoke or be near an open flame while using it and you will be fine. Theres no harm in being over cautious but it is really not dangerous.

[multiweb]

Very good to know - thanks for the info. What's your take on acetone for aluminium coated mirrors?

[MJ_]

I dont use acetone as a cleaning product so I cant give you an accurate answer. All solvents will do pretty much the same job so i think its a bit useless trying to compare them when the end result is the same. If you are worried acetone is going to do anything to your coatings just stick to isopropanol.

Also that Badder 'Optical Wonder' is just a mixture of isopropanol and ethanol, so dont waste your money on that either there is nothing special in it.

[leon]

Hey guys, I think all this cleaning of lens stuff is well over the top , I clean my Tak and the other accessories Taks with a OPSM glasses cloth, with a very small spray of normal Windex, been doing this for years.

Crystal clean every time, and no smears, and no damage,save your dollars.

Did you know that when one takes out the filter in front of the sensor of a 5D, that they are nearly indestructable.

I tested mine that I took out because I did not need it any more as I replaced it with the IV/UR replacement.

I took it to the shed dropped it in acetone, metho, petrol and kero, rubbed it clean, with an old cloth, took it inside washed it under the hottest of water with dish washing detergent and dried it with a tea towel.

Not a mark was visible, but I'm sure there were some small marks that I could not see. :shrug:

The point is you can handle filters and the like and clean them with ordinary stuff, they are much tougher than led to believe. ;)

Below is an image of the filter I removed and abused with a bright light shining through the rear

Leon :thumbsup:

[floyd_2]

Hi guys,
just in case anyone is looking for Isopropyl Alcohol and can't get it from a chemist, sign writing suppliers sell it for cleaning cars etc prior to applying vinyl to them. I used chemist supplied isopropyl alcohol for cleaning my naglers etc for years. When I finally ran out, I just started using the isopropyl from my local sign writing supply shop. I paid about $10 for 1L.

As far as I can tell, this isopropyl leaves no residue at all (first tested on an old eyepiece). Any residue in a cleaning product like this sold by an automotive vinyl distributor would no doubt stop their vinyl from sticking to cars properly. I do sign writing from time to time and also use this isopropyl for cleaning vehicles as the final stage before vinyl application. It leaves them squeekey clean with zero polish etc left on the surface.

Dean

[stephenb]

I too have used isopropyl alcohol for years, but I have used Windex also (I think you've posted this somewhere before Leon?? I'm sure I came across your Windex advice somewhere on IIS before :thumbsup:). I have used Windex successfully on previously owned GSO instruments without any issue whatsoever.

[marki]

I have been thinking about this for a while and after a number of scientific experiments I can highly recommend .......... SMIRNOFF :). Yes after many exhaustive tests vodka cleans your lens like nothing else and if it all goes pear shaped you have the answer in a bottle right next to you :drink:. Try it and see for yourself, you will be amazed at the results.

Mark

[multiweb]

Yep - totally agree. Smirnoff is not good for anything else. I wouldn't drink it. Zubrowka is the only way to go when it comes to Vodka. ;)

[mickqueensland]

Hi guys,
interesting discussion.

Marki, what "mild detergent" do you recommend and what strength solution?

Cheers
Mick

[Outbackmanyep]

I used to use Isocol, which is found in the supermarket, but recently (in the last 4 years) i have been using mild warm soapy water.....

[mswhin63]

Isocol is rubbing alchol, I use it for certain cleaning, but i wouldn't recommend for lenses as it contains other chemicals other than Isopropyl. Usually best pure Isopropyl.

I would think soapy water on a lense would leave a residue on it. Mirrors are a different matter though.

[marki]

Any dish washing detergent will do but your mirror would have to be filthy before I would go beyond deionised water. Wouldn't try vodka on your mirror though as the ethanol will react with the aluminum coating.

Mark

[floyd_2]

I always used just one or two drops of liquid detergent in distilled water when I cleaned my newt mirrors in the past, nothing more. Just enough to break the surface tension of the water.

Dean

[avandonk]

One thing that I have not seen mentioned in this thread is that why Isopropyl Alcohol is so good as a solvent cleaner is it's rate of evaporation. Ethanol or Acetone will condense any contaminants in the local atmosphere onto your optic surface due to their high rate of evaporation at normal room temperature.

Isopropyl Alcohol evaporates at a rate where it forms a 'protective' cloud of solvent vapour so no contaminants can condense or settle on your optic surface.

All antireflection coatings are porous at the molecular level so will incorporate contaminants. Some are better than others. It depends on the vacuum deposition method.

A plain Al coating will form oxide within seconds of exposing to air (oxygen). A 100nm Aluminium Oxide layer will form after a couple of days. The reflectivity will drop from 90%+ to about 84% or less over time. As an over coating for Al, SiO2 is deposited as SiO and this converts to SiO2 over time.

So NEVER clean a freshly coated mirror until many weeks after coating.

Pinholes in coatings are the main reason for deterioration as contamination eats away at the glass coating interface.


I spent many happy years producing vacuum coatings at Kodak in the Reseach Lab so I most probably have forgotten more than I know now.

Bert

[batema]

Hi,

If you use Isopropyl alcohol on a refractor do you have to worry about the alcohol near the edge of the lens seeping into the holding groves???? and if using cotton wool makeup circular pads is there a particular pattern you should follow first?

Mark

[Outbackmanyep]

Hi Mal,
I use the warm soapy water on my 10" dob, and it works fine on the 8" SCT, i haven't had any problems, i rinse with distilled water which is a must. I stopped using Isocol about 4 years ago before i bought my 8" SCT, i never used it on my 10" dob, i used to use it on my 60mm refractor though....
I'll just keep using soapy water.

[GeoffW1]

:rofl::rofl::rofl:the mind boggles :eyepop:what were the punters DOING ?

I recall years ago doing a St John's First Aid course. We got to the bit about spider and snake bites, where the accepted wisdom (then) was to wash off the bite.

The instructor said "use anything available, even urine", at which some wag at the back called out "Step 1 - piss on the patient !!"

Cheers

[GeoffW1]

Hi Bert,

How does that work? I'm not doing a leg pull honestly, because I see you have that experience, but.........?

Cheers

[GeoffW1]

Hi Leon,

I think yes, dead right :thumbsup:

I was steered that way by other sites as well, like Cloudynights etc, when I took my C8 to bits.

Greasy fingerprints everywhere, delicate surfaces, ooohhhh what have I done ?

That formula worked fine. A bit of dilute acetone with distilled water was need at one point for a smear of Nulon grease :P but all was well.

Cheers

[GeoffW1]

Ha,

4 in a row :lol: