Friday, July 19, 2019

The Eyes Have It: A Technological Appendix to Postblogging, April 1949

Two things from last month that are obviously much more interesting than Standard Telephone and Cable's version of that new American gizmo, the "transistor."* They are mercerisation, which is one of the more common, yet mysterious, ways of treating cotton textiles, and a complicated Barr and Stroud optical gadget that no-one would call a household device, but which is still interesting from the point of view of trying to understand how a machine can do what it does. I tell you, these "robots" and "automatic machinery" today!

(STC  led to Alam Blumlein, "inventor of stereo," commemorated at "historic Abbey Roads Studio)

And now the fold . . . 
. . . So I can post big pictures without worrying about the front matter. That I haven't fiddled with in years.

These ladies are modelling traditional Indonesian batik wear. It's almost certainly Mercerised cotton at this point, but Mercerising isn't a traditional part of batik. Or is it?


Mercerised cotton top by Zalora. I apologise for the lack of glam. Standing around like a clothes hangar seems to be the default approach to modelling mercerized pictures. The men in t-shirts do better with what they have, but here I exercise my male privilege. 
So John T. Mercer is a pretty darn obscure guy, for someone who is making me reach for the "Shift" button so often to commemorate his awesome sciencing. He acquired one of those High Victorian biographical memoirs in 1886, E. A. Parnell's Life and Labours of John Mercer. It seems like I should know who Parnell was, but not so much. There are plenty of other famous Parnells, but E. A. is just some kind of chemist. He's behind an 1840 paper on the "preparation of inulin," that I'm going to leave to the link on account of the bibliographic matter being too much typing, but that's it. So he's some kind of chemist, and was really, really old by 1886. That probably tells you what kind of book we're reading the details of Mercer's life from. He's so old that his digestion could probably benefit from a regular source of inulin! Which I mention mainly to point out that inulin now has competition amongst the superfoods from turnips. Because turnips are inherently funny.)

Chintz top By Nasty Gal
Ahem. Per Wikipedia channeling Parnell, Mercer was born in 1791, died in 1866, was married to Mary Wolstenholme in 181. They had six children, and he did various things and was memorialised in various ways as to suggest that he was pretty well off. Wikipedia describes him as being "very fond of dyeing," which seems like an odd hobby, but who am I to judge? My good old Britannica more usefully identifies him as a calico printer. If reference to a British calico printer doesn't ring a bell, I would suggest taking the radical step of clicking through the link, where the reader will encounter Wikipedia's summary of a long-standing accusation (Nehru is cited) that British tariffs against imported Indian calicos played a crucial role in de-industrialising India. Contemporary relevance! 

The kind of flouncy effects the reader
probably associates with "chintz" and "crepon."
Otravez by Di Anna Elardo.
Mercer was brought up in the heyday of European calico printing, by which time focus had turned from the original problem of copying Indian printing patterns to the production of fashionable, "small, tight patterns" as the market moved away from chintz. I mention this because,of all the effects immediately produced by "Mercerizing," the most obviously salable one was, per the Britannica, the production of "permanent crimp or 'crepon' effects."

I guess I'm burying the lede here, because the point is that "Mercerising" fell into obscurity at some point after 1844 because Mercer just used it for these crepon effects, which weren't enough to sustain its use. Mercerising was revived and patented by H. A. Lowe in 1889/90, and then again by Thomas and Prevost in 1895, who finally made a success of it. The patents were subsequently annulled on the not unreasonable grounds that it had already been invented. 

So, way back in 1844, Mercer described the process as an attempt to filter 50°Tw caustic soda through fabric at roughly room temperature. While the results for the solution he was trying to filter are not recorded, the material he was using as filter showed shrinkage, increase in strength, in crease in hygroscopicity, and an improved uptake of dyes. The shrinkage, however, was a bit of a downer. The revival of the 1890s came along with machines that automatically grabbed the pieces of cotton and held them so that they couldn't shrink on exposure. (Insert technical language here.) The resulting pieces had an increased lustre (and were also, as far as I can parse the language) were also harder. It is the lustre, mainly, that distinguishes modern Mercerised from non-Mercerised cotton. That being said, it is often used in bandages and "medical" socks, which seems like it has more to do with the "hard hand." See! I am following the jargon, even if I have no idea how or why a fabric would have both a "hard hand" and a "soft hand."

If you're wondering about "Tw," it is the abbreviation for "Twaddell," which is a hydrometer scale for measuring the specific gravity of a liquid relative to water. It is named for W. Twaddell of Glasgow, who was the first to produce hydrometers (for the British industry, at least) on an industrial scale, back at the turn of the Nineteenth Century. Here's the Wikipedia article on the subject. Also, hey! HEY! A Glasgow instrument maker! That's a link to Barr and Stroud!!! 

So it's a weird, industrial measurement used in the British dye and bleach manufacturing sectors. Also, W. Twadell had the good sense to design a slide rule, once upon a time. I say good sense because slide rules are much more collectable than hydrometers, and I now get to piggyback on someone else's research (the best part of these technological appendices).

David Rance of Slide Rule Gazette tells me that William Twaddell (1792--1839), apprenticed in the shop of James Brown, "renowned Glasgow instrument maker") before branching out on his own. He is first known to the collector from a set of "philosophical bubbles," which is a matched set of eighteen hand-blown glass bubbles. You throw them in the retort, and the one that floats to the surface  tells you the specific gravity. As you keep adding one thing to the other thing, one bubble after another floats to the top, until you get the one you want, at which point you should stop adding. Philosophical bubbles were a well-known product, marketed to the spirits and liquor industry. Subsequently Twaddell made hydrometers

The Twaddell hydrometers Mr. Mercer would have used. 
Rance went to look at a set at the museum, and has found descriptions of their use in the tanning and pottery industry in recent years. This was as much an attempt to find out more about the Twaddle scale and the slide rule in his collection as to learn about Twaddell hydrometer sets, but now we know what we know.

Again, it's just my inference that Mercer used his Mercerising process to make flouncy, chintzy fabrics suited to early Victorian tastes. That, plus it is an excuse to put that nice picture up! When Mercerisation was reinvented, it was because they had those grabby things that prevented shrinkage, but also because caustic soda was a lot cheaper.  What I am circling back on is that going to come back to here is the notion that exposing fabrics to the effect of  "concentrated caustic soda" was some kind of novel discovery of 1844.  Traditional batik-making involves

 "Firstly, a cloth is washed, soaked and beaten with a large mallet. Patterns are drawn with pencil and later redrawn using hot wax, usually made from a mixture of paraffin or beeswax, sometimes mixed with plant resins, which functions as a dye-resist. The wax can be applied with a variety of tools. A pen-like instrument called a canting (Javanese pronunciation: [tʃantiŋ], sometimes spelled with old Dutch orthography tjanting) is the most common. A tjanting is made from a small copper reservoir with a spout on a wooden handle. The reservoir holds the resist which flows through the spout, creating dots and lines as it moves. For larger patterns, a stiff brush may be used.[18] Alternatively, a copper block stamp called a cap (Javanese pronunciation: [tʃap]; old spelling tjap) is used to cover large areas more efficiently.[19]

Emphasis mine. "Caustic soda" has another name, after all: soap. Or, rather, it's the active ingredient in that somewhat magical stuff. Home-made NaOH solutions have been used to treat fabric for a long time before Mercerisation was thought of. In fact, I've cut off a subsequent use of caustic soda in the preparation of indigo dye from the indican precursor produced from natural indigo plants. What Mercer discovered was a specific post-production treatment of a specific kind of cloth. As we learned from Fortune, there was a raging debate about just what Mercerisation did to cloth that continued into the 1940s and the invention of the electron microscope. From this perspective, I'm at least open to the idea implied by some sources, that what Mercer was trying to do was develop a new way of filtering caustic soda. In short, he was trying to improve caustic soda production with a view to making more of this essential material available to the existing textiles industry, for work such as calico printing. Instead, he stumbled on a new way of using caustic soda to produce a unique and valuable textile product.

It's  a story, anyway. It's also bound up in the instruments. Mercer has a new set of Twaddell hydrometers that allow him to assess the merits of a caustic soda solution in a new way. He sets out to produce caustic soda at a specific Twaddell number, and ends up showing that caustic soda of a certain Twaddell rating has this novel effect. Mercerisation helps sell the Twaddell scale, and Twaddell hydrometers.

John Brown may have been a "famed instrument maker," but good luck tracking down a specific Glaswegian named John Brown. By the time Archibald Barr and William Stroud were "approached by the Admiralty with a request to develop a short-based rangefinder" in 1891, Mr. Twaddell had been out on his own for more than seventy years, and, well, speaking of the latest run of Engineering, here's a link to the 1896 edition of The Electrician Electrical Trades Directory and Handbook, so you can see that there were lots of people and firms named "Brown" in the trade in Glasgow by then. This was two years before Archibald Barr was called home to Glasgow to take a chair at the University, and three years before his revived connection with Stroud, a former colleague at Leeds College, led to the opening of a manufacturing facility in Glasgow to produce the already-mentioned rangefinders. 

Unlike some of the other old firms we've followed up on around here, Barr and Stroud didn't move into a palace:
which is nice, because if they had, they would have outgrown the Anniesland neighbourhood, and I wouldn't have an excuse to post this aerial:

Mid-Eighties Anniesland. Quaint! Photo from the blog, Lost Glasgow, by Dennis Thompson.
Lomb factory in Rochester, New York
The building seems a bit underwhelming considering that Barr and Stroud were making binoculars for the Army by that time, but what do I know about the appropriate size of an optical firm? 

If I understand it properly, the multiplex stereo mapping equipment consists of several projectors mounted above a movable tracing table, which is above a drawing table. The projectors are fed with several overlapping aerial photographs, which are projected in blue and red onto the tracing table and then [something something] adjusted so that they show one particular datum, or elevation, which becomes a bunch of blotches. Trace the outlines of those, and you have all the given contour lines at that elevation on your final mapsheet. Keep on adjusting to produce slices of at each contour line, and eventually you will have a complete contour map. 

Now that's Dieselpunk. Source.
By simply feeding "multiplex stereo mapping equipment" into my stationary Google machine, I was led to this handy pdf. Apparently, the United States Geographical Survey's first multiplex stereo mapping equipment was crucial to the success of the TVA. There was no other way to map the Tennessee Valley on the scale and accuracy necessary, at least in the time available. No TVA means no atomic bomb, so from tiny acorns, mighty oaks, etc. I have no idea if the USGS got its equipment from Barr and Stroud, although I know that before that, they had an Aerocartograph  made in Germany. By 1949, the USGS's R. K. Bean was working on the ER-55 projector, which, as of this writing, you can get on E-Bay for $160 plus shipping and handling. Some nice person has put Bean's full account up as a pdf. Bean says that the key problem was one of making mirrors to the required accuracy, and that it was eventually solved by precision electroplating. It was possible to make glass lenses to the right, very complex shape, but plating the lens with the right thicknesses of blemish-free copper and silver required new departures in electroplating technique. 

It's too bad that we don't have a similarly loving description of the multiplex stereo mapping equipment used by the USGS previously. It might well have been made abroad, as the USGS had a distinct preference for Zeiss equipment at the time. But it turns out that by attaching "Barr and Stroud" to my search, I am led to a bonanza of work coming out of the Barr and Stroud archives. Fancy that! Here's a snip from Petrie's Short History of British Stereo Plotting Instrument Design that was Archibald Barr's initial contribution to the problem.

Barr was working for the War Office, which had developed an interest in mass producing good topographical maps during the World War, in aid of the overarching objective of killing more Germans. However, it seemed worth continuing after the end of the war, and a figure that soon pops u is none other than Canada's ever-controversial Lieutenant General E. L. M. Burns. Which just goes to show that whenever I read a placeholder in Flight about just how many square miles the RCAF has mapped that particular year, I am being introduced to an actual old-time Canadian contribution to the advance of science. 
The Wiki article doesn't really get at the
sheer assholeness of the man.

 Barr's work was cut short by his death, after which Burns became an important driver in the process, because Canada was a very interested potential customer, something hard to come by in those depression days. The men who working with Barr at the War Office were thus inspired to develop the "stereogoniometer," which doesn't seem to have matured by 1939, when two semi-prototypes were installed in a facility at Southampton and worked until they were blown up in the blitz. More work must have been done afterwards, and after the remit of the article I am summarising, or the Secretary of the Army wouldn't have patented it in 1968. 

I'm going to sign off on this one at this point. There's a huge public literature. It's all very technical, and there are a great number of instruments to consider that are really hard to tell apart unless you're deeply invested in the field.  A number of British researchers continue to mine the Barr and Stroud archives, but their work has limited general appeal due to that technical complexity. It is all, of course, built on an earlier mastery of the production of optical glass, and thus upon the heavy chemical industry and its ability to supply high quality caustic soda. That's where we come in, and it is --almost-- where I leave. 

The "almost" arises from Nehru's old denunciation of the prohibitive calico tariffs that supposedly birthed the British industry whilst deinustrialising India. (And Java, too, taking batik into account.) If the argument is accepted, the Barr and Stroud connection shows that we cannot limit the damage to just one field. Instrument makers profited from the development of mercerising, and all the other chemical post-production textile treatments like it, and went on to be the foundation of new industries in very different fields. The "No photogrammetry means no TVA means no atom bomb" through line is very lazy and hackish, but that doesn't make it wrong! 

*Noodling around Wikipedia, it looks as though STC's interest in the transistor starts with Alec Reeve's pulse-code modulation, which he was working on before he moved on to GEE and OBOE, which have just had their plugs pulled by the Air Ministry. Maybe STC has some spare technology left over from that project, and is rustling up custom?

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