Stripping aluminum coating from primary mirror.

[Lumpy Darkness]

I leaned last night that Bob First alcoat webpage now says he is not costing at this time.  I then found the subpages on the website seem to be gone.  Anyone know Bob's status?

I was looking for directions on stripping old coatings.  I believe Bob had such info on his site.  Anyone know the process?   I think it's basically an acid bath.

Thanks,

Mark

[Jonathan Lawton]

Here's what the wayback machine has to say: https://web.archive.org/web/20210514223817/http://alcoat.net/al_2-0.htm

Jonathan 

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[Lumpy Darkness]

Thanks Jonathan.  My phone autocorrected Bob's last name: s/b Fies.

[John Pierce]

IIRC, Bob uses a concentrated solution of ferric chloride (PCB etchant).    most mirrors have a silca or other overcoating, this means it will take much longer to strip.

phew, if Bob Fies has quit, I heard that Optic Wave Labs had their vacuum chamber die unrepairably, and they aren't likely to resume coatings, and I don't think 1800destiny is doing coatings anymore either.

Bob did my Coulter 10", and I have zero cmplaints.     ok, I met him twice, and he talked my ear off each time, but thats OK, it was entertaining.

OWL did the club's 20" Obsession's Galaxy mirror with a 96% coating, and that came out just awesome.

OH!   Bob used to hand out this floppy disk with his 'Astro program' on it, basically a bunch of local/static web pages with notes on various things.    I took it upon myself to post a copy here for my own personal reference.

https://freescruz.com/astro/web_tele/alt_00.htm

Bob's coating removal instructions are here...

https://freescruz.com/astro/web_tele/alt_15.htm

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[Matthew Buynoski]

Aluminum is prone to corrosion by chlorine containing chemicals. Probably the quickest is hydrochloric acid, though this stuff is somewhat dangerous to work with; it’ll dissolve you with gusto, too :-) The fumes are also not fun. It is often sold in hardware stores as “muriatic acid."

[John Pierce]

On Sat, Sep 9, 2023, 6:05 PM Matthew Buynoski <buyn...@batnet.com> wrote:

Aluminum is prone to corrosion by chlorine containing chemicals. Probably the quickest is hydrochloric acid, though this stuff is somewhat dangerous to work with; it’ll dissolve you with gusto, too :-)  The fumes are also not fun.  It is often sold in hardware stores as “muriatic acid."

It's also available from swimming pool supply places in gallon jugs, it's used to lower the pH of a pool after chlorine (sodium hypochlorite) raises the pH 

[Donald Gardner]

Aluminum was the primary metal used for interconnects in integrated circuits until more recently when the technology switched to copper and a couple of other metals. The aluminum interconnects were formed on top of silicon dioxide (similar to the glass in a mirror) and were patterned using either a dry etch process or a wet etch process.  The wet etch process was designed to not etch silicon dioxide and uses a mixture that consisted primarily of phosphoric acid, a relatively mild acid.  The etch rate is highly sensitive to temperature, but readily etches at room temperature.  One can easily find premixed aluminum etchants on the web such as from Sigma Aldridge:

https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/318/803/901545-product-info-mk.pdf

With best regards,

Don

On Sep 9, 2023, at 3:08 PM, Lumpy Darkness <itsmar...@gmail.com> wrote:

I leaned last night that Bob First alcoat webpage now says he is not costing at this time.  I then found the subpages on the website seem to be gone.  Anyone know Bob's status?

I was looking for directions on stripping old coatings.  I believe Bob had such info on his site.  Anyone know the process?   I think it's basically an acid bath.

Thanks,

Mark

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