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Old 11-07-2014, 08:56 PM
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doppler (Rick)
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DIY Mirror silvering

This old 10" meade starfinder was salvaged from the tip/recycle centre for $50 with a badly corroded primary mirror. After a acid wash and a home re-silver the primary is seeing light again. A fair bit of coma but it is a F4.5. 23 X 20sec @ iso 3200 mounted on eq pier with RA drive only

Rick
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Old 12-07-2014, 07:59 AM
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torana68 (Roger)
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awesome bit of recycling !!! how much did the chemicals cost?
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Old 12-07-2014, 08:13 AM
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Could you please describe the process you followed? I have a 16inch that is in desperate need of resilvering.

Trent
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Old 12-07-2014, 11:19 AM
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I have just had this 20" recoated by Wayne Sainty at Saintech. Prices are very reasonable.
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Old 12-07-2014, 01:10 PM
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Thanks Barry
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Old 12-07-2014, 07:09 PM
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Originally Posted by torana68 View Post
awesome bit of recycling !!! how much did the chemicals cost?
The dearest part is the silver nitrate @ $75 per 25 grams (but you only need about 5 grams to coat a 10" mirror) The other chemicals needed are nitric acid, ammonia, sodium hydroxide, distilled water and glucose. Nitric acid is recomended for cleaning the glass prior to coating, but is hard to buy in small quantities. I have been using hydrochloric acid as a substitute. Ammonia is also hard to obtain, liquid or as ammonium nitrate. I found that the soap used in "black and gold" cloudy ammonia settles to the bottom and clear ammonia can be decanted. Sodium hydroxide is drain cleaner and is on the supermarket shelf and pure glucose is cheap at the chemist. Nitric acid dissolves silver so if you could obtain some you could recycle the coating or even make your own silver nitrate by letting the acid evaporate from the dissolved silver.

Here is a short clip showing the chemical silvering proccess that I have adapted to coat my mirror.
https://www.youtube.com/watch?v=6vduHWV47Dg

This process is ok for a quick cheap fix , it only lasts for a few months and the coating can be easily rubbed of. Aparently there is a chemical that will condition the glass for a stronger bond but I have only found it on o/s mail order sites. I am not sure about custom regulations about importing chemicals.
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Old 13-07-2014, 02:54 AM
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The dearest part is the silver nitrate @ $75 per 25 grams (but you only need about 5 grams to coat a 10" mirror)
Ouch!
These guys do a few kits for pour or spray coating. Their most basic pouring kit will coat 8 sq feet for ~$18.
http://angelgilding.com/A2101.html

Their basic spray kit will do 133sq ft for ~$80.
Much more than anyone would use within the 1 year shelf life
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Old 13-07-2014, 06:48 AM
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The gubmint doesn't trust mere mortals with nitric acid any more. It has become very hard to get, and when you find it, very costly with exorbitant courier charges - more than the HNO3 itself!!!

Ammonium nitrate - good luck. You can make things go boom-bye-bye with it. Therefore, we aren't allowed to have it easily.

Sulphuric acid is hard enough now to get too.

i use HNO3 and H2SO4 a lot in my hobby of firearm restoration. You make rust blue solution with these 2 combined, plus some other ingredients. I have to buy 3 litres of each... adds up real fast
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Old 13-07-2014, 07:41 AM
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Mackay is minnig supply town, I can get nitric acid and concentrated ammonia but only in 20 litre drums at about $200 each, but I only want a litre of each.

The silver nitrate is $60 for 25 grams, the source is in melbourne postage and packaging took it up to $75.

It costs me about $15 each time I recoat and the unprepared chemicals have a shelf life of many years. A new mirror for the 10" is about $350, but the scope has the old cardboard tube and a crap focuser, not worth fixing when a new dob is $650.

I picked up this old 8" dob at a garage sale on friday for $60. The primary mirror coating was completly gone, you could see the cell behind it. Resilvered it that arvo and was looking at the moon and saturn that evening. The mirror is an old full thickness one so might be worth getting the proper aluminium treatment.
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Old 13-07-2014, 12:33 PM
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Originally Posted by MrB View Post
Ouch!
These guys do a few kits for pour or spray coating. Their most basic pouring kit will coat 8 sq feet for ~$18.
http://angelgilding.com/A2101.html

Their basic spray kit will do 133sq ft for ~$80.
Much more than anyone would use within the 1 year shelf life
I have checked that out and it doesn't look like they ship outside the US or Canada.
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Old 13-07-2014, 12:55 PM
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I have checked that out and it doesn't look like they ship outside the US or Canada.
Sure they do, you can't use the shopping cart tho;
http://angelgilding.com/International_Orders.php
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Old 13-07-2014, 04:38 PM
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Thanks, I'll bookmark that link. I have enough chemicals to last me for a year or so. Looks like its worth a try at that price.
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Old 13-07-2014, 04:43 PM
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Smile

I have received several shipments of their product. Highly recommended. So easy to do. Safe and simple. 13 Months and still some viewing time left on my last application.
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Old 13-07-2014, 07:26 PM
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I have received several shipments of their product. Highly recommended. So easy to do. Safe and simple. 13 Months and still some viewing time left on my last application.
How well does the coating bond to the glass? I find that with my method you can't touch the coating too much or it either peels or rubs off. I have ordered some stannous chloride which apparently conditions the glass to let the sliver bond better. I got a good 6 months out of my first effort and even then it was only showing a tinge of yellowing, but still quite usable.
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Old 14-07-2014, 05:05 AM
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How well does the coating bond to the glass? I find that with my method you can't touch the coating too much or it either peels or rubs off.
This is supposed to help: http://angelgilding.com/A2044.html
I've not used any of it yet so can't comment on how well it works.
It was Stephen that put me on to these guys, cheers Stephen
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Old 14-07-2014, 06:47 AM
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This is supposed to help: http://angelgilding.com/A2044.html
I've not used any of it yet so can't comment on how well it works.
It was Stephen that put me on to these guys, cheers Stephen
Great, thats the stuff I have ordered from the UK, but in powder form (stannous chloride) http://rover.ebay.com/rover/0/e11400...xe=exe,ext=ext
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Old 14-07-2014, 08:04 AM
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Quote:
Originally Posted by doppler View Post
How well does the coating bond to the glass? I find that with my method you can't touch the coating too much or it either peels or rubs off. I have ordered some stannous chloride which apparently conditions the glass to let the sliver bond better. I got a good 6 months out of my first effort and even then it was only showing a tinge of yellowing, but still quite usable.
Hi doppler,

no problem with bonding to glass. Glass preparation after thorough cleaning and subsequent application of "Tin for silver" (probably "stannous cloride") the end result is good.

Even managed a mirror clean without doing much damage to the surface.

PS Hi MrB(Simon) Your glass there yet?
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Old 14-07-2014, 01:34 PM
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PS Hi MrB(Simon) Your glass there yet?
Hi Stephen, yes the glass arrived thru the week, many thanks. I haven't had a chance to get a square drive tool to remove the screws you have used. It looks to have arrived in one piece, but a thorough inspection will follow after I source the tool.
In the mean time I'm trying to decide which machine to build, a MoM style or a Fixed Post (Gordon Waite style) machine. The fixed post looks perfectly capable in youtube vids, so is the type winning me over at this stage.
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Old 14-07-2014, 01:37 PM
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I just realised the Long Life 'Tin for Silver' I linked to above can't be shipped internationally.
Oh well, I'll just have to order the standard version. Due to the short shelf life of many of the chemicals, I'm holding off my order until I'm closer to actually needing it. There's a lot of glass to remove in the meantime.
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Old 17-07-2014, 08:51 AM
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Please let us know your next step.. I need to fix my 12 inch nbut will also wait a bit aseven if I had product today work cant yet proceed.
I am glad to see this thread I was about to throw the lot out.except focuser ..I chped the tube setting up brakets and the thing was a sorry sight. Great to think I can use it again.
Mice got in and pee d on the mirror I was only away for 3 weeks and I thought it was well covered...It was heart breaking
alex
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