Bob Fies on Aluminizing Mirrors

So now you have your new mirror ground, polished, and figured. Now what does it take to get it aluminized? For many amateur telescope makers in the SF Bay area, the answer involves Bob Fies. Bob coats mirrors for John Dobson of the Sidewalk Astronomers, and for the Chabot Telescope Makers Workshop, as well as for individual customers. I once took a mirror to Bob and stayed to watch the whole process. It was an interesting time. The flash of aluminum vapor in the vacuum chamber seen through the porthole was especially fascinating.

Bob will be addressing us on January 6. He will step us through the process, including cleaning and prepping the mirror, installing the mirror and aluminum in the vacuum chamber, flashing the coating, and applying the protective overcoat. Related topics include care of the mirror, durability of coatings, and stripping for a recoat.

How did Bob get involved in the mirror coating business? I thought his reply to my query was worth repeating, so here it is:

When I went to Carlmont HS in Belmont in the 50s the science teachers were very energetic. Those were the days when they had the Science Fair at the Academy of Science where the new planetarium had just been finished. One of the many projects at Carlmont was to grind and aluminize an 8 inch mirror for the school. The teachers had collected various bits and pieces for the project including a mercury diffusion pump which luckily we never got into operation.

The other influence at that time was the Peninsula Astronomical Society. That was before Foothill College and they met at the Center at the Park at Embarcadero and Middlefield Road in Palo Alto. Several ‘National Aeronautics Administration’ scientists from Moffet Naval Air Station attended along with Stanford professors. One of the people, Robert Jones was particularly involved in telescope making, even starting a business, Vega Instrument, to manufacture Maksutov telescopes. Marvin Van whose 16 inch telescope ended up in the dome at Foothill College was also a member.

So after a few grubby jobs I ended up in a good paying union job as a mechanic with Pan American Airways in 1964. At that time vacuum tubes were the main stay of electronics but there were people putting more than one transistor in ‘discrete devices’.

So at about 1966 I decided to build a vacuum system to experiment with. I was thinking of making capacitors or transistors or thin film magnetic memory and also providing a way to coat telescope mirrors. At that time they were using things like silane and arsine gas to ‘dope’ transistors and I didn’t want to have that stuff in my parent’s house. So I tried a bit of ZnS / cryolite dielectric optical filters but the sulfur made the aluminum coatings come out dark. It was at about that time that Mr. Dobson showed up with a bunch of 8 1/2 and 9 1/2 porthole mirrors to be aluminized. His great enthusiasm overcame my lethargy at that time and I more or less gave up on other vacuum projects and concentrated on mirror aluminizing. At that time all mirrors jobs were new mirrors as there were not a lot of used mirrors around as there are now.

So over the years I continued coating as a side line until Pan Am went bankrupt in 1991. At that time the mirror coating became more of a profession for me and a serious enterprise. Eric, one of the young sidewalk astronomers that was then at Stanford, persuaded me that I must be on the internet. The internet has turned out to be the perfect way to allow potential customers to find my service.

So that’s the history of ‘Aluminum Coating’.

Bob’s web site is at http://home.covad.net/~alcoat/index.htm .