A loupe is basically a magnifying glass without a handle. In the case of watchmakers’ loupes they are designed to be held to the eye either by the folds of skin around the eye or by some sort of mechanical device. They may also be known as eyeglasses or eye loupes.
Magnification
There’s a whole range of magnification. The higher the magnification, the closer the loupe will be to your work. Loupes may be referred to in terms of magnification or focal length.
You should use a magnification to suit the job you’re doing and probably shouldn’t use the higher magnifications for long periods.
I tend to work with a X, because I can see the whole pocket watch movement in the field of view, but I have collected a range of them over the years and will often swap between them, depending on the task in hand.
Byran G Sweazey (Chicago School of Watchmaking) recommends a 3” glass. Donald de Carle, Fried
Types
There are myriad types of eyeglass. You will pay more for aplanatic lenses which have been designed to avoid distortion:-
Some have screw on or push on lenses which means the lens can be removed for thorough cleaning.
Some have threads enabling a second lens to be added to increase magnification. There seem to be three reasons why anyone would buy a double lens:-
Economic – you get two for the price of less than two
Practical – instead of swapping loupes and having the new one steam up on you, you just add to the one you’re wearing.
Technical – the two lenses are matched to reduce distortion (certainly in the case of the Seitz jewel inspection eyeglass)
Remember, though, that the second lens is invariably smaller and that your field of vision will be reduced.
Some are made especially for inspecting jewels (10x and 20x) and are often tinted blue (Bergeon make some for Seitz).
Basically, you get what you pay for. If you’re likely to be wearing one for most of the day then it would make sense to buy the best you can afford to minimise strain. If you’re only going to use it occasionally (and I’ve heard of some who don’t generally use them at all – they must be young!) then why pay more than you need to?
Holders
There are a number of different holders:-
Stainless steel wire – I tend to use these at the moment. They’re simple to use, but watch out for the coil end; it’s sharp and will mar the casing of the watch glass unless it is filed smooth.
Stainless steel strap – a more sophisticated version of the wire and at a more sophisticated price!
Rubber strap – I’ve not tried this one as yet, but it doesn’t look as comfortable or as easily removed as the steel wire one.
One of the problems I have is that I have to wear glasses to see anything on the bench, so I need to be able to quickly remove a loupe for brief moments.
Spectacle frame clip ons – these are lenses encased with clips of various mechanisms for use with glasses. The Ary, made by Bergeon, are over £70 each, so I haven’t tried them yet! A*F do a much simpler and cheaper version.
Manufacturers
A*F (Swiss), Anchor (Indian), Asco (blue tinted, Swiss), Bausch & Lomb (founded in 1853 in Rochester, New York), Bergeon (Swiss), Coil (UK), Eye (German), Horotec (Swiss), Peak (USA), Schweizer (German).
Prices range from £1 upwards. Horotec make a range of wooden eyeglasses; each one costing around £60. So, as usual with watchmaking equipment you can spend a fortune or just enough!
It really isn’t worth buying these second hand.
Further Reading