MicrobeHunter.com Microscopy Forum

I just wanted to point out something some new collectors, like myself, may be unaware of.
The Spencer microscope on the left has a rich copper coating over the brass which is beautiful and cuts some of the glare.
The Bosch and Lomb binocular scope is a restoration. This one was in very bad shape, the paint on the prism housing was pulled off in chunks from people taping department labels and such and ripping them off. The prism cover had to be stripped, polished and painted. I had to buff the paint off with an emery tip on a rotary tool because B&L’s chemically resistant paint actually shrugged off xylene! (Always use eye protection, mask, and gloves outdoors. I use Canada balsam and so cannot get away from it, and I try to keep exposure limited.) But I digress.

The brass was so corroded it had black stains and pimples. I had to use Brasso to clean the stains, which brings me to the point of this post:

Brasso removes tarnish from brass, but it also quickly and efficiently dissolved the copper coating!

I also had to polish the pimples off the corse focus knobs with a soft tip on the rotary tool and red polish paste. This still left microscopic tool marks which made them look foggy. I hand polished them with diamond paste, followed by several coats of Renaissance Wax. Note the difference in reflective glare. And the naked brass surface will require more maintenance as it will tarnish more quickly



So in conclusion, never touch a copper coated brass microscope with any kind of brass polish.
The copper coating responds well to Renaissance Wax which is a micro crystalline metal polish.
Several coats rubbed on and off will make brass, chrome, rhodium, or black microscope paint really pop in the light.

I hope this saves someone some grief.
Radazz

A better angle.

Radazz wrote: Brasso removes tarnish from brass, but it also quickly and efficiently dissolved the copper coating!...
So in conclusion, never touch a copper coated brass microscope with any kind of brass polish...

Yes. Brasso and similar silverware and copperware polishing materials contain ammonia, as is evident from their smell. Ammonia dissolves metals.
I have used it on ornamental copper items ("Alladin's" lamp, etc). Unless you finish it with some protective coating, a grey-green patina reappears within a day. I finally applied a coating of thin transparent lacquer and the item is still shiny like new, after 3 years. But for a working microscope there should be better solutions.

Both Spencer and B&L used a type of lacquer over the brass parts, which has a yellow to orange tint, possibly derived from the same traditional sources as Urushi lacquer ; iron oxide and or cinnabar. The tint of the lacquer was not consistent, ranging from a mid orange to almost the colour of the brass itself. It may fade over the years depending on the exposure to light. I have found that isopropyl alcohol and sometimes a bit of highly diluted toothpaste and a small soft toothbrush works well on it. I have also used some plastic polish, such as plast-x , which is designed for those plastic headlight lenses.

Spencer also had some gold plated apochromats, between about 1925 and 1955, which I don't think were lacquered.

I do believe that the "copper" coating, which you refer to, is actually just the lacquer which Apo refers to. As the lacquer ages, it also can get darker. The Brasso is taking the lacquer off along with with blemishes and it also will take paint off, so you need to be careful. After getting down to bare metal, you should give it a coat of lacquer and you won't need to keep polishing it.

Cool! Thanks for the info.
This forum has been an invaluable resource.

Radazz,

Good job on your polishing. Looks great.

Just as an aside, if you are interested in re-applying lacquer to parts of the microscope, you have a choice of using a modern lacquer, or using one formulated in accordance with more old-timey techniques. Below are two pages from my venerated copy of Scientific American Handy Book of Facts and Formulae (ed. by Hopkins), 1918, pertaining to the lacquering of brass. The p.269, item 11, even mentions pale gold (q.v., p.268) as the best for microscopes.

If nothing else, it would provide hours of fun and excitement, especially digging up the materials (e.g., Dragon's Blood resin). I would definitely experiment with small amounts, on small areas, to perfect your techniques before committing to the larger areas of the scope.

Oh man! That’s fascinating, And some truly bizarre ingredients.
But it’s a delight to the imagination

I've run across an internet based company that sells many of those old fashioned and hard to find products:

http://www.woodfinishingenterprises.com/

I haven't bought from them, but bookmarked them because some of their products can be used for processing specimens and making permanent slides.

What others have indicated is true regarding the warm copper tone of the brass components of the vintage, "unpolished" scope. That hue/patina is due entirely to shellac that was applied over the polished brass as an anti-corrosive. I am a machinist and fine mechanic specializing in optical instrument repair. Years ago, I did a great deal of "ghost" repair work for a microscope repair business (that's still in business) in Florida. The primary reason for them sending me stuff to repair was that, especially on the old Leitz 600 series condensers - where the tiny iris leaves are practically at the bottom of a well - their aging repairman lacked the dexterity to re-assemble them... I liked the guy and he had trained as an apprentice at Vickers in England and would describe the atmosphere in the various departments of that company before the war. I had one of these old brass scopes in my shop to regrease and I asked him about *that* finish and he described a huge room housing a large bench with bunsen burners and women who would apply stick varnish/shellac using no brushes but only the heat of the burners to melt and drip the varnish on components where, due to the heat, it would coat very evenly while they rotated the parts. He further added that, because he was a teenager at the time, he had no desire to learn the technique and regretted it ever since!