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 Post subject: Time for a recoat
PostPosted: Sun Aug 24, 2008 8:44 pm 
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I made the mistake of cleaning my mirror without rinsing it with distilled water, and the coating got hazy. Luckily, Bob Fies at "Aluminum Coatings" in San Carlos, CA. is inexpensive, and does a great job. I'm bringing my mirror down tomorrow for a fresh coat. Probably the last one for awhile, since I'll have to ship the mirror from Hawaii in the future.

Just a reminder- when cleaning your mirror, rinse with distilled water!!! :grin:

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PostPosted: Sun Aug 24, 2008 11:17 pm 
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I take it the haze couldn't be rinsed off with distilled water during a recleaning? I guess I don't understand how a failure to rinse could cause permanent haziness on a mirror.

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PostPosted: Mon Aug 25, 2008 5:23 am 
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One of the reasons I've developed a preference for refractors is the potential for problems with mirrors.

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PostPosted: Mon Aug 25, 2008 7:39 am 
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The chemicals in tap water damage the coatings. Once it's allowed to dry, the haze is permanent. The thing is, I know better. When I last cleaned the mirror, I simply forgot to rinse it with distiller water, which was sitting in the jug right next to the mirror. :foreheadslap:

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-Erik Wilcox
Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
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Evolution is both fact and theory. Creationism is neither. -Anonymous


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 Post subject:
PostPosted: Mon Aug 25, 2008 8:19 am 
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Really? The last time I washed my mirror....I simply placed my 22" against the tree and simply hosed it down and let it runoff and dry, my coatings didn't haze.

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 Post subject:
PostPosted: Mon Aug 25, 2008 8:55 am 
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It would depend on the water content. Aluminium is highly reactive and quickly forms an oxidized coating measurable in nanometres when exposed to air; however the the presence of some catalysts can lead to a deeper reaction and some chemicals can have a nasty effect. Salt water for instance slowly eats into unprotected aluminium and if left to react long enough the result is a vaguely green goo. This was a common problem on some classes of post-WWII minesweepers built with a composite wooden hull and aluminium frame to prevent triggering magnetic mines.

My guess would by that either your water supply contains fewer chenicals /lower concentrations or your mirror has a thicker protective coating than Erik's had.

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The Irish Constitution... is written in the present tense. You reason it in light of this year, not in light of the year in which it was adopted by the people. You don't need to hark back to what some people thought thirty or forty years ago.
Brian Walsh, Supreme Court Justice 1961-90

O....o?oo


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 Post subject:
PostPosted: Tue Aug 26, 2008 8:31 am 
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Great explanation John. Thanks. I've often wondered what effect the minor amount of sea spray at the Winter Star Party in the Florida Keys has on coatings and have cringed when watching folks wiping encrusted residue from correctors and such. The stuff must be slightly abrasive is nothing else!


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 Post subject:
PostPosted: Tue Aug 26, 2008 3:36 pm 
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Put it this way- after looking at the local water table brocure they send every year, I'm not at all surprised that it would damage mirror coatings. :lol:

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Homebuilt 16" Truss Dob
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SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
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"Newt Gingrich is what stupid people think smart people sound like."
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Evolution is both fact and theory. Creationism is neither. -Anonymous


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 Post subject:
PostPosted: Tue Aug 26, 2008 4:15 pm 
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But you're in San Francisco, so your water supply should be from Hetch Hetchy Dam and the pristine Tuolumne River. ???

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Ah, but I was so much older then.
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Best tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg


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 Post subject:
PostPosted: Tue Aug 26, 2008 7:55 pm 
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Pristine? Is arsenic considered pristine these days? :lol:

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Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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 Post subject:
PostPosted: Wed Aug 27, 2008 8:37 pm 
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Sodium, calcium, iron, and magnesium are the most common dissolved minerals in water. Stuff like arsenic may not be good for you, but we're talking parts per million concentrations, which would probably not be visible on a mirror.

I'm assuming the the mirror had a silicon monoxide overcoating?

If so, you probably ended up with some silicate minerals on your coating: sodium silicate, calcium silicate, and magnesium silicate all form fairly easily. There might also be some carbonates in there, with sodium and calcium carbonate being the most likely.

If the water's really bad, you might have some sulfates/sulfites in there too. Yuck!

Some of these might polish away, but I wouldn't trust them to always do so without damage.


Bob Fries doesn't overcoat his mirrors, does he? He did my 10" about 4 years ago, and I'm happy with it, but I don't remember whether that step was included.


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 Post subject:
PostPosted: Wed Aug 27, 2008 9:04 pm 
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I'm not sure if he applies an overcoat. I'll have to ask him. :)

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Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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 Post subject:
PostPosted: Wed Aug 27, 2008 9:57 pm 
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quasar
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??? The SFPUC's 2007 water report summary says arsenic was below detectable levels.

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Ah, but I was so much older then.
I'm younger than that now
Bob Dylan

Image
49.6 mpg avg over 38,000 miles. 177% of '08 EPA
Best flat drive 94.5 mpg for 9.8 mi
Best tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg


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 Post subject: Re: Time for a recoat
PostPosted: Fri Sep 05, 2008 8:31 pm 
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Erik wrote:
I made the mistake of cleaning my mirror without rinsing it with distilled water, and the coating got hazy.....
Just a reminder- when cleaning your mirror, rinse with distilled water!!! :grin:



Yowsers! :shock: Thanks for the warning. I have always done the distilled water rinse but this will reinforce my habit.

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 Post subject:
PostPosted: Sun May 03, 2009 10:49 am 
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What about demineralised water? Anybody has experiences with that?. I see it readibly availble over here but i cannot find distiled water easlily. Perhaps at the local pharmacie but i don't know if they are willing t provide it by the gallon....(liters)

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 Post subject:
PostPosted: Sun May 03, 2009 6:10 pm 
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fmeireso wrote:
What about demineralised water? Anybody has experiences with that?. I see it readibly availble over here but i cannot find distiled water easlily. Perhaps at the local pharmacie but i don't know if they are willing t provide it by the gallon....(liters)



Try the pharmacy. Most pharmacies in the States carry it. And it's cheap, I pay less than $1/gallon.

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 Post subject:
PostPosted: Mon May 04, 2009 12:16 pm 
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Hi Freddy,
I hope you find the demineralized water. :)

As an update to my original post, I had Bob Fies recoat the mirror and it looked great. But he doesn't use an overcoat, and I was afraid of it getting damaged again. As I was planning the move to Hawaii at that point, I didn't want to have to ship it back to the mainland to get a recoat. So, while I was still in California, I ended up having Cary from OWL strip the new coating and do a recoat with an overcoat. He's the guy that refigured the 1/2 wave beast into the 1/8.5 wave beauty that it is today, and he did a great job on the recoat as well. In fact, I was so impressed with his new facility in Sacramento, that I'm planning on writing an article about it for ATT. He has some state of the art equipment, and an unbelievable amount of knowledge on everything optics-related. :cool:

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-Erik Wilcox
Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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