Distilled vs deionised water

[Physopto]

Kim Wipes if necessary, use once and throw away.

Big BUT! It depends upon using them correctly. There is a very precise method. Drape the Kim wipe on the surface gently and slowly drag across the surface. Do NOT rub!

There is a better discussion on line somewhere. It takes practice to do correctly and would be a costly mistake if done wrongly!!!!!

But they are only used after the mirror is washed clean and rinsed. They are used to take of the last few drops I believe. I have never done it!

I use them on lenses and filters when needed but when absolutely necessary and I haven't as yet, I have "First Contact Polymer Solutions Optics Cleaner".

Derek

[hughgilhespie]

Hi,

I would be a bit cautious about using water purified by reverse osmosis alone. As I remember from my boating days, a yacht RO unit would produce 'drinkable' water but it always tasted very salty. Maybe the kit has improved but this is a quote from a current advert for a '5-Stage Reverse Osmosis' kit

'For Pure Water 0 TDS reading why not add a De ionization Filter To your order'

TDS is Total Dissolved Solids and for optical cleaning you really need that to be a big fat ZERO!

Regards, Hugh

[Mrbloke]

What about WFI?

 

 

[RikM]

Deep sigh putting on 'work' hat.

Distilled water is an outdated method of producing 'purified' water of no specific classification.

Type 3 water, RO, basic DI and filtration, has a resistivity of > 0.05 MΩ-cm,  <1000 ppb silica, <200ppb TOC (total organic carbon). This is used for rinsing glassware, filling heater baths and as feed water for more advanced systems.

Type 2 water, multistage DI and filtration, has a resistivity of > 1.0 MΩ-cm,  <100 ppb silica, <50ppb TOC. This is used for standard reagents, microbiological culture media preparation and for preparation of reagents for chemical analysis. Used in clinical analyzers, cell culture incubators. Also suitable for rinsing optical components.

Type 1 water, multistage DI, UV treatment, Ultrafiltration etc, has a resistivity of > 18.0 MΩ-cm,  <10 ppb silica, <20ppb TOC. This is used for critical analytical reagents, mammalian cell culture, IVF and other clinical applications.

WFI (water for injection) is somewhere between type 2 and type 3. Has a resistivity of around 0.75 MΩ-cm and is subject a loads of different regulations but generally low purity compared to analytical grade water.

 

I work for a major scientific equipment manufacturer and help design ultrapure water systems for a living. if you normally use labwater with a 'Q' in it, I work for the other guys  

 

[triton1]

Even deeper sigh after reading that head starting to implode my first quotation methinks.I use de ionised no problem.

[Ouroboros]

Frankly I'm sceptical.  I think it unlikely that contaminants in deionised water will be present at sufficiently high concentrations to damage or corrode the mirror surface, or indeed to significantly reduce the mirror's reflectivity.  The main purpose of using deionised or distilled water is to rinse away calcium and magnesium carbonates that can be left as a visible residue after cleaning with tap water.  Deionised or distilled water will do that equally well. I usually find the deionised water I use barely wets the surface of the mirror - it simply flows off when I leave the mirror to drain and dry. 

Now, my background (in part) is in surface physics. The old joke in surface physics is that 'God made solids and the devil made surfaces' because surfaces are notoriously difficult to keep clean.  As soon as you prepare a "clean" surface it becomes contaminated with all sorts of organic molecules and goodness knows what from the atmosphere.  Admittedly I haven't done detailed comparative tests of mirrors repeatedly cleaned with deionised and distilled water. Has anyone?  What I'm saying is a best guess ....... Reinforced by the observation that using deionised over several years appears to have no deleterious effect.  So in a way we are doing the comparative tests ourselves.  Let's see whose aluminised mirror surface drops off first shall we?  ;-) My bet is that one of us is more likely to drop a mirror or scratch it during the cleaning process than we are to damage it with the water we're using. 

[edarter]

Wow, didn't expect to kick off such an excellent discussion! Thought it would be a cut and dried answer ☺ Very informative!! 

[Dave In Vermont]

Last Words Dept:

From me - at least: I recommend you use distilled as a final rinse. DI-H2O certainly won't hurt, but if it's what you got - it's what you got. And I surely agree that unless cleaning is not needed - Don't!

Many, if not most, damage is incurred to mirrors and/or lenses is caused by well-meaning people who don't understand a bit of dust or something that "doesn't look clean" is not a reason to try to clean a optical surface.

I'll also say that using a torch/flashlight to look at a mirror/etc. will often make an utterly clean optical surface resemble a WWI battlefield.

 

"Gasmasks ON, Boys!"

Dave

[Stub Mandrel]

On 24/01/2016 at 16:55, davedownsouth said:

NB.  If anyone lives in the North Hampshire area, I am happy to let them have as much DI water as they want; they have to come and get it though, water is heavy to ship 

Thanks, I'm sending over a few tankers for some of your heavy water.

Kim Jung Il

[Peter Drew]

Here's some chronological testing. I've been cleaning mirrors, when necessary, for over 50 years. I've always used tap water and either soapflakes or washing up liquid followed by rinsing with distilled water. Never, as far as I recall, have I damaged the surface or reduced the longevity. I think the lifetime of the reflective medium is largely determined by the initial quality.

[davedownsouth]

7 hours ago, Stub Mandrel said:

Thanks, I'm sending over a few tankers for some of your heavy water.

Kim Jung Il

It's true, when water is ultra-pure it has a density of 14.2; slightly more than that of mercury 

[Physopto]

9 hours ago, Peter Drew said:

Here's some chronological testing. I've been cleaning mirrors, when necessary, for over 50 years. I've always used tap water and either soapflakes or washing up liquid followed by rinsing with distilled water. Never, as far as I recall, have I damaged the surface or reduced the longevity. I think the lifetime of the reflective medium is largely determined by the initial quality.

And I should think by careful handling....

 

[pete_l]

I doubt that it would make any material difference. So long as there aren't any particles (grit, pieces of limescale) in the water that could scratch the surface. Since you will be drying the surface after cleaning - rather than letting it dry by evaporation, any residue will be absorbed onto the cloth / paper  towel / cotton-wool that takes the water off. Just remember to dab, not rub.

The amount of "stuff" in the quantity of water you'll be using - even straight from the tap - will be infinitesimally small and the mirror coatings are pretty tough and inert.