Has anyone tried this?

[azrabella]

The final rinse after cleaning a primary mirror was done with "distilled" water from a condenser tumble dryer. It seemed to work as there appeared to be no noticeable residue or water marks left after the mirror had been allowed to air dry. Has anyone else tried this? Only reason for asking is that it is quite difficult to obtain commercial distilled water readily and I regularly produce about 5 litres costing nothing, which normally gets thrown away.

[wulfrun]

Completely different purpose but I use it to run model steam engines. I live in a very hard-water area and boilers scale up quite quickly on tap water. One side-effect is a slight aroma of fabric conditioner so I suspect the water is less-than-pure distilled. Never tried it on a mirror, telescope or otherwise. Don't see whay it wouldn't work though and if you have no marks afterwards I'd say it's all good. Melted ice collected from defrosting a freezer would also be fairly well distilled.

[Zermelo]

It's an interesting idea.

The principle makes sense - water vapour condensed from the air results in pure water(?).  I haven't had to wash a mirror yet, but I did have a similar idea a while back - I tried using the water condensed in our electric dehumidifer in place of the de-ionized water we used to buy for the steam iron.
I have a conductivity meter, so I tested (a) our normal tap water, (b) de-ionized water and (c) water from the dehumidifer.
The commercial de-ionized water read just about zero, whereas the dehumidifier water, although much lower than our tap water, was certainly not zero.

Perhaps the dehumidifier water was picking up material from the innards of the machine. If you can see no residue from your procedure then it sounds like you're OK.

[laudropb]

I would worry that there would still be impurities there and that mirror coatings could be damaged.

[azrabella]

...then maybe good quality bottled drinking water is pure enough. I'm thinking  "smart water" or Aquafina? Technically these are regarded as pure.

[DaveL59]

1 hour ago, azrabella said:

...then maybe good quality bottled drinking water is pure enough. I'm thinking  "smart water" or Aquafina? Technically these are regarded as pure.

most drinking water will have impurities of some sort, be that mineral or even bacteria. None will be anywhere close to distilled or de-mineralised as you can't or should not drink either of those as they are likely to cause your body issues if consumed in significant quantity. 

I'd also agree with @laudropb about impurities in the output from a condensing drier, dust and any chemical from washing/fabric additives that find their way into the evaporation mix. No telling what the longer term effects of this coating the mirror surface will be. In some ways the closest would be aircon or dehumidifier condensate, but even this has the potential for bacteria build up in the internals over time.

It should be possible to order distilled water from Amazon should you need it, most local garaged and hardware around here only to de-mineralised. From what I read this is more active so perhaps less ideal, but once opened and after a couple of weeks de-mineralised becomes distilled in nature so should be fine and I've used this on mirrors with no issues.

[Shimrod]

8 minutes ago, DaveL59 said:

most drinking water will have impurities of some sort, be that mineral or even bacteria. None will be anywhere close to distilled or de-mineralised as you can't or should not drink either of those as they are likely to cause your body issues if consumed in significant quantity. 

I'd also agree with @laudropb about impurities in the output from a condensing drier, dust and any chemical from washing/fabric additives that find their way into the evaporation mix. No telling what the longer term effects of this coating the mirror surface will be. In some ways the closest would be aircon or dehumidifier condensate, but even this has the potential for bacteria build up in the internals over time.

It should be possible to order distilled water from Amazon should you need it, most local garaged and hardware around here only to de-mineralised. From what I read this is more active so perhaps less ideal, but once opened and after a couple of weeks de-mineralised becomes distilled in nature so should be fine and I've used this on mirrors with no issues.

Or alternatively de-ionised water which you can pick up from Asda in the car section for about £2. I've used it on my LX90 without issue, although there is a de-ionised vs distilled debate. Couple of links to threads on here:

replacement for distilled water

cleaning primary mirror

 

[DaveL59]

20 minutes ago, Shimrod said:

Or alternatively de-ionised water which you can pick up from Asda in the car section for about £2. I've used it on my LX90 without issue, although there is a de-ionised vs distilled debate. Couple of links to threads on here:

replacement for distilled water

cleaning primary mirror

 

ah probably de-ionised was what I was referring to rather than de-mineralised, but yes there's a degree of debate on the merits of the easier to obtain de-ionised stuff.

[Stu]

7 hours ago, azrabella said:

The final rinse after cleaning a primary mirror was done with "distilled" water from a condenser tumble dryer. It seemed to work as there appeared to be no noticeable residue or water marks left after the mirror had been allowed to air dry. Has anyone else tried this? Only reason for asking is that it is quite difficult to obtain commercial distilled water readily and I regularly produce about 5 litres costing nothing, which normally gets thrown away.

I’ve always sourced RO (reverse osmosis) water from the local aquarium which is really cheap and easy to get hold of. Seems a safer bet to me.

[Zermelo]

34 minutes ago, Stu said:

I’ve always sourced RO (reverse osmosis) water from the local aquarium which is really cheap and easy to get hold of. Seems a safer bet to me.

as used by my window cleaner (on my windows, not on his primary mirror).

It doesn't leave any marks, but not sure how pure it is vs. distilled/deionized.