Wray London Loupe

[Stephen]

A nice vintage Wray London magnifying loupe, with adjustable sleeve casing, to match the focus to the focal plane, used mainly for examining glass negatives. Bought cheaply on Ebay.

The glass elements are in very good condition, but the black paint on the sleeve needs a re-spray, and the aluminum eyepiece and knurling, needs a good clean and polish.

Magnification is not marked, but seems to be approx 20X. I suspect it dates from pre-war period, the war time ones are Ministry arrow marked. They were used for examination of aerial reconnaissance negatives and plates in the war.

Stephen

[philbirch]

A lovely object, rather than a re-spray I'd be inclined to strip the paint off and see if the brass can be polished up first. It may look good that way. Try paint remover - doesn't always work on cameras though.

[Stephen]

It appears that Wray made these for dual use, examining negatives, but also to check the exact focus on a view camera with a ground glass focus plate, like 5x4 or larger.

I think it best left black, I can strip it easily with Nitromors, oven cleaner, or caustic soda, and clean the brass with citric acid, then spray with oven baked synthetic enamel and oven bake the paint, and then polish with fine rubbing compound, almost certainly the way Wray did it. I doubt if an undercoat was used.

The Citric acid is used as it is safe, the old trade "cleaner" was a mix of nitric, sulphuric and hydrochloric, mixed with soft soap (BPC)grade, Ammonia, and then made neutral with caustic soda. The mix produces an etched surface with a fine crystal granular appearance, and was beloved by instrument and clockmakers, for the very best brass finishes.

Do not try this mix at home!!it is lethal if mixed wrong. I suspect it is banned under UK Health and Safety regulations these days.

My last job before retiring was working at Leeches Scientific equipment and lens makers, who made, and finished very similar items. The Wray optics are un-coated, plain glass, the quality indicated by three glass elements and large diameter outer element.
Stephen

[daveh]

Caustic soda is bad enough but a combination nitric, sulphuric and hydrochloric acids would give a super-duper aqua regia, presumably one of those mixtures than would dissolve everything. They are now looking for something to keep it in.

[Stephen]

May 19, 2014 3:08:42 GMT -5 daveh said:

Caustic soda is bad enough but a combination nitric, sulphuric and hydrochloric acids would give a super-duper aqua regia, presumably one of those mixtures than would dissolve everything. They are now looking for something to keep it in.

Mixed in glass, and after being made neutral, stored in tins! Diluted with distilled water to suit the etched surface required. Obviously made up in small quantities. There was a commercial mix done for clockmakers, and other nitric/sulphuric based mixes for dipping brass after silver soldering, for instant dissolving of borax flux.
All very nasty in the wrong hands!

In my youth we had to dispose of 500 gallons of sulphuric (battery strength), from a GPO exchange, the local Sussex council did not allow simple disposal, so it was driven tank by tank by me in a Morris van to Kent, where it was poured down the drain, via a caustic soda "filter" dam made of sacks of the stuff... it did a wonderful job of clearing the drains! Such disposal is strictly banned these days........

Stephen

[Stephen]

Finding the details of old processes is an interest, the statement that the do not make this any more and the method is lost, really annoys me!!

Metal blackening, etching or oolouring were considered black arts, trade secrets, many processes coming from the art world, used by Victorians to "fake" bronzes patina etc., or came from gunsmiths who loved "processed steel". With brass the best users were clockmakers and jewelers makers.

I was surprised to find out in the leading London gunsmith's workshop that the very best barrels were blackened by old used woolen socks, applied dry, and rubbed on to red hot steel. The smell was indescribable....but Purdey barrels were done that way! Proper gunblack by carbonisation, not a chemical in sight.

Stephen.

[daveh]

Old is often good. Old is often improved on over hundreds of years. New can be better, but sometimes it isn't. It's a skill to keep the best of the old and incorporate the best of the new.

A J Rudge, the father of a friend from school was a chemist with, I think, ICI. Fluorine was his "thing". The manufacture and use of fluorine and its compounds, was written in the early sixties and had a few photos of people who had accidental exposure to hydrofluoric acid. That isn't too nice a substance either, even though it's much less well known that the big three. I'm not quite sure what applications HF can be put to but I image it is good for most of those cleaning and etching operations.

[Stephen]

Hydrofluoric Acid, used to etch glass and in production of glass ornaments and special lenses, and precursor of PTFE, and fluorine compounds, also used to vulcanise rubber in specialist O rings, very nasty acid indeed, but useful in processes....