[LVAS] Mirror Making - Part 3

[Fred Rayworth]

Gary,

 

Wow! Someone is actually reading them! Thanks.

 

I like your top to bottom storage method. It isn't that bad to have to have the different grits in different rooms, but you need to keep them at least moderately separated, that's for sure.

 

It's going to be tough to keep away from fans, especially in the Las Vegas area, but in other parts of the country... You won't really need to worry that much about it.

 

However, when we get to the polishing, don't matter if you are in a virtual oven, NO FANS for sure!

 

As for Barnesite, I used it on my 8" mirror along with rouge. I don't remember the Barnesite being radioactive at all, but that was in the 60's and I didn't have a geiger counter. It seemed to be a pretty common polishing compound, at least in the Telescopics mirror kits.

 

Cereum oxide is definitely more aggressive than rouge, but it also speeds up the rough polishing a good bit. In my case, on my 16", it helped tremendously. I used rouge for the smoothing later on and for the fine figuring. You just have to test a lot, but the sped up results can sure save time. I'll get into that more in a few articles.

 

As for preformed blanks, those can save a lot of time in hogging out the curve. All you need to do then is rough grind to match the mirror curve to the tool and you're off. However, premolded blanks are almost always f/4 or f/4.5 nowadays, so you are limited to whatever that curve is. I remember at one time some companies offered f/8 blanks and a few other focal ratios. For the f/7 example I use in the articles, I have never seen a blank offered with a pre-generated f/7 curve.

 

Mirror making is definitely not a cost saving measure, at least if you buy a kit. In the case of my 16", I found the blank in a junkyard and got it for free. I made a tool out of 1/4" plate glass epoxied to thick plywood discs. I scrounged the rough grit from a sandblaster. The only things I ordered were the finer grits, pitch, and polising compounds from Willmann-Bell. Total cost of making that scope, including the coating, was $250 stretched between 1984 and 1987. 

 

Thanks again for the comments.

 

Fred

 

 


 


Date: Fri, 19 Mar 2010 20:39:04 -0700
From: voliton at gmail.com
To: lvas at lvlug.org
Subject: Re: [LVAS] Mirror Making - Part 3


Hi Fred,
 
Excellent articles. I may actually give it a try. Definately not a way to save money though. Blanks seem to run about 70% of a good finished mirror so when you add all the materials and coatings - forget about the time and energy. Mirror making requires true dedication to the art of DO-It-Yourself.
 
As a long time Lapidary hobbiest I have several comments and questions. The only good way to store grits and polish, aside from being in seperate sealed rooms, is vertically  - coursest on the bottom and polish on top. This minimizes possibility of contamination. Also, no fans in the room.
 
I am a little surprised  at the preferance for Cerium Oxide as a polish. It is very aggressive and I reserve it for gems 8 or above hardness. Linde A would seem like a better choice at .3 micron size. Linde B might be a bit of overkill at .05 micron.
 
I never heard of Barnesite. Turns out it is a mineral associated with uranium ore and, as such, 
is moderately radioactive - sort of like wearing 25 radium dial watches for twenty years.
 
Any comment on the preformed blanks which seem to have become popular? 
 
Regards,
Gary 



  		 	   		  
_________________________________________________________________
Hotmail is redefining busy with tools for the New Busy. Get more from your inbox.
http://www.windowslive.com/campaign/thenewbusy?ocid=PID27925::T:WLMTAGL:ON:WL:en-US:WM_HMP:032010_2
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lvlug.org/pipermail/lvas/attachments/20100320/820427cb/attachment-0001.htm