Is De-Ionised Water OK for Mirror cleaning?

[Alan White]

I wish to clean my newtonian mirror and when I went to look for distilled water today was only able to find de-ionised.
I know they are different, but is de-ionised ok for the final mirror wash over?

If it is not OK, can someone point me at a supplier.

Thanks, Alan

 

[happy-kat]

I think halfords do distilled water though check the ingredients as it is meant for the radiator system in cars.

[paul mc c]

I wouldnt use anything only chemists distilled water,sterile and pure,you would get this in most chemists,I just done mine last night,used 2 ltrs and came up like new.

[paul mc c]

Should add,I use it for rinsing only.

[IanC11]

Wash with either distilled or de-ionised water but use Isopropyl Alcohol  for rinsing. 1 ltr tins available from Maplin Electronics.

Once rinsed just allow to stand for 5 mins as it evaporates away leaving a dry, clean mirror. Also to help the cleaning try to get hold of medical grade cotton wool balls. Only use each ball for ONE gentle pass across the mirror face then discard.

[Ouroboros]

In my view deionised is fine. I have used deionised water to rinse the 200mm mirror in my SW reflector everytime I've cleaned it on maybe four or five occassions during the last 7 or 8 years. I shall carry on using it as an experiment. If the mirrored surface deteriorates, or the glass melts, I will let everyone know. 

[Alan White]

Thanks all.  
Appreciated as always. 

[scarp15]

Distilled Marine, RO type III, obtainable in 5L bottles, available through aquariums at local garden centres. Upon the first time I cleaned my mirror, I bought a 5L bottle after which refills are free. Dry with cold blow setting on hair dryer straight after.

[niallk]

I got a bottle of distilled from Boots.

I'm in the wrong business: expensive stuff! 

I washed my 10" mirror as practice before doing my 15".  Only the 15" got a final rinse with the expensive distilled water; I used deionized for the final rinse on my 10".

The 10" was perfect - like new No doubt distilled is the purist option, but no issues with deionized, and I too blew water droplets off the glass with a hairdryer on cold and the corner of a sheet of kitchen roll sucking anything stubborn up.

[faulksy]

i used distilled ,pharmaceutical grade. bought it on line. around 7quid a gallon. and from my local chemist medical grade cotton wool . loooks lke new

[saac]

5 hours ago, Alan White said:

 

If it is not OK, can someone point me at a supplier.

Thanks, Alan

 

Alan, you can source distilled or deionised water on Amazon. Prices vary quite a bit for distilled so worth looking through all the listings.

Jim

[N3ptune]

I found this webpage about distilled water and deionized.. I can't really make up my mind 100% but I would be tempted to use distilled water instead of de-ionised for my mirrors. Sometimes in my country we can buy distilled directly on the shelves for 2.50$ each bottle like this one bellow, very cheap, but it's rare, most of the time the only choice is deionized.

https://www.thoughtco.com/distilled-versus-deionized-water-609435

They say this about deionized:

- As you can see, in some situations either distilled or deionized water is fine to use. Because it is corrosive, deionized water is not used in situations involving long term contact with metals.

- washing glassware, especially the final rinse

- While it's okay to drink distilled water, you should not drink deionized water. In addition to not supplying minerals, deionized water is corrosive and can cause damage to tooth enamel and soft tissues. (I was not aware of the dangers or drinking deionized.. surprising)

- Deionized water is reactive, so its properties start to change as soon as it is exposed to air. Deionized water has a pH of 7 when it is delivered, but as soon as it comes into contact with carbon dioxide from the air, the dissolved CO₂ reacts to produce H⁺ and HCO₃^-, driving the pH closer to 5.6.

I did the cleanup of my mirrors one time with deionized and honestly it did absolutely no apparent damages to my mirrors.

[Ouroboros]

I doubt weak acidity makes much difference since we are rinsing and drying the mirror quickly. So the water is not in contact with the mirror for very long. And anyway - as reported on this website - distilled water will also absorb carbon dioxide from the air to become a weak carbonic acid with a pH of about 5.8.  Moreover the tap water we use to clean and carry out initial rinses may have a pH anywhere between about 6 and 9. 

[barkis]

Until you feel yourself very capable cleaning that valuable disc of glass, don't be tempted to rub the surface with anything. It's surprising how vulnerable the coatings can be, and minute scratches can easily be made. Thorough rinsing in tepid water can often suffice to clean it, if any marks persist, repeat the cleaning process. A final rinse off with IPA should complete the job. Stand the mirror on it's edge to allow the water to run off. Any globules remaining can be picked off with the corner of a tissue.        Bear this in mind though, a dirty mirror can perform better than a badly cleaned one.

[triton1]

I used de ionised water without any problems at all,angle the mirror in the sink quick rinse it will be dry in a couple off minutes and no streaks.

[Ouroboros]

I sometimes wonder whether the deionised versus distilled versus reverse osmosis water debate in astronomy circles is like the gold versus copper versus silver speaker cable debate in hi-fi circles.