Retrotechtacular: Crystals Go To War

More than one of our readers suggested we highlight this beautifully-shot process documentary about the laborious and precise manufacturing of piezoelectric quartz crystals in the early 1940s. Just a few years later, Bell Labs would perfect a method of growing synthetic crystals, sending droves of brave men and daintily-handed women from the Reeves Sound Laboratories to the unemployment line.

Early radio equipment relied upon tuned or L-C circuits for clocking. These were prone to drift by a few kHz, which prompted the use of crystal oscillators for stable frequencies in the 1920s. The lives of our armed forces and those of our WWII allies depended on reliable communication equipment, so the crystal oscillators they used were top shelf, produced by hand from Brazilian crust.

splat-crepesEvery step of the way, from raw, freshly-mined quartz crystal to mil-spec engineered crystal units, these minerals are sorted, inspected, verified, cross-checked, and so on. Before any cutting takes place, they undergo testing to determine their optic axis, which is clearly marked with a black dotted line. This procedure also reveals imperfections such as twinning. Every subsequent cut is made with the orientation of the optic axis in mind.

Once the crystal wafers are about an inch square and seventeen thousandths of an inch thick, they are lapped with liquid abrasive until are thin enough to achieve the desired frequency. Finally, they are tested for performance in extreme temperatures and sent tumbling down a vertical maze to see if they fall apart from shocks.

[Thanks for sending this in, Fred and ar0cketman]

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

51 thoughts on “Retrotechtacular: Crystals Go To War

  1. They sure spoke oddly back then.. “pie-ah-a-zee-oh”, “Ah-sala-scope”. But then again, the narrator sounds like he is eating lunch at the same time so maybe it is just him.

    1. I grew up with my grandparents who were of that generation. I don’t remember them or anyone else ever talking like that, yet almost all of the period documentaries I’ve seen had narrators that did. Something they teach in film school perhaps? Ridiculous Pronunciation 101 maybe?

    2. Maybe he was disguising his voice. Judging by the opening credits around 0:20, they wanted him to be anonymous:

  2. I loved the shots of the perfectly manicured and painted nails on the women. It may be an industrial job, but that’s not going to get in the way of looking good.

    1. They made a cut where he is putting his face shield down, but in the next shot when he actually goes to make the cut you can clearly see that he’s flipped it back up :(

  3. These crystals were in great abundance in the surplus stores back in the 1950s and 1960s. You can still find a few at ham radio flea markets today.

    The joy was bending the frequency by grinding to raise the frequency, or lowering the frequency by carefully applying graphite from a pencil. I used to use Comet cleanser and plate glass for the grinding. I still have a drawer of crystals that were used in a 2 meter transmitter which multiplied the base frequency by 18. So surplus military 8 MHz crystals were perfect once they were adjusted to the appropriate frequency. has more info on this amateur technique.

  4. @ 35:14 to 36:50 How did the timed exposure to a powerful beam of X-Rays lower the frequency ?

    Were some atoms changed from silicon to another element, and that tweaked the frequency down ?!?!? The longer the exposure the more atoms changed or was it something else ?

    1. The X-Ray’s introduced damage into the crystal structure altering it’s resonant frequency downward. Longer they got X-Ray blasted – the more damage – the lower the frequency.

      1. The thing I find terrifying (for the girls) is that crystal x-ray analysis and/or tweaking probably irradiated many of them to an early grave. The frequency-lowering jig gave me the Herbie-jebies: to wit the small size of the head of the instrument indicated that the likely x-ray (gamma ray, actually) source was radiological (likely a Cobalt 60 source). Anything hot enough to alter crystalline quartz (even on a small scale) wouldn’t be the the kind of thing I’d sit next to and make notes in a logbook.

        1. I was thinking something similar about the liberal use of x-rays with the users present. I wouldn’t want to be that tech that’s for sure! Today what safety info isn’t being provided to employees in states like China?

  5. Now that video is cool… Let me tell you a story about manufacturing crystals in the 70s:

    In the early 70s, I worked in a Crystal factory in Kansas City Kansas. I had all of the jobs at the factory during my high school and college studies. Generally, I worked full time on the swing shift but the midnight shift was more fun. This factory, in its era, was making mostly 3.579 Mhz crystals for Color TV. Some 32khz clock crystals but at least 75000 color TV crystals per DAY. Big color TV demand at the time. We had one competitor in Brazil doing about the same volume at the time.

    Obviously, the technology had moved enormously since the 40s. Labor was hugely reduced though several processes were still manual. i have to say: Labor didn’t look that good in the 70s… I guess that is also obvious. We did have the same cavalier approach to acids, TCE and safety though all of the xRay steps had been eliminated.

    some differences in Mfg flow:
    1) by the 70s, all raw quartz processing had been converted to “synthetic” crystal growth. baskets full of chunks of raw quartz, mostly clear were put in the bottom of vessels (basically ammonothermal growth vessels) with 6″ long 1/8″ square seed cuts of the desired orientation hung on strings in racks on top. Raised to temp and pressure… 22 days later, 4 strong high school boys would open the vessels using sledge hammers to loosen and, a crane, to unscrew the machined aluminum plug (12″ diameter, 12″ deep, fine thread pitch)… and Wollllaaa, you got 500 or so crystal rocks about 150mm long, 30mm wide and 18mm tall.

    2) These rocks went into a splitter/squaring saw… down the center long ways and then squared into nice “perfect” square rectangles
    3) these were double checked as to orientation… then diced at the proper angle into square crystal blanks maybe 1.5mm thick

    4) these went to Rough Lap… Strong High school boys ran these laps. Cast iron plates like they showed in the video but the “carriers” with the pentagonal holes were plastic… about 60 square blanks were done at once with a pot of mineral oil/ SiC powder dripping through holes in the top plate. the top plate weighed about 40 lbs but slowly ground down to about 25lbs when we replaced it. High school boys would spin off the plate and put it back 330 times per night. My shoulders and arms were very impressive at the time. We had these beat up old short wave radios wired to a sensor arm that attached to the top plate. when the “Noise” from the crystals during grinding got to the right intensity… the lap would shut off. we unload and reload and go again.

    5) these blanks were then stacked in a pressure vise (maybe 150 of them) and put in a “Lathe” that made the crystals round

    6) Crystals thrown into a tumbler … Brass tubes 10″ diameter with dry SiC powder to knock off the sharp edges
    7) crystals cleaned and then into the “Fine” lap. these had light weight plates (machines generally run by women singing country songs about men and sex and generally enlightening a naive high school boy)
    8) Crystals back into a “fine” tumbler to make “lens” shaped blanks.

    9) Cleaned… sent to the Silver evaporation department… a keyhole shaped dot of silver was placed placed and overlapped in the center with the long part of the keyhole sent to the edges of the crystal for the attachment of “Legs”
    10) wire clips (legs) held in a plastic base were clipped onto the crystal… then run through a tuning system of measuring-etch silver- measure – etch silver cycle until they were in tune.
    11) add the metal can over the top… measure/test/mark and ship.

    I left out all the toxic chemical baths and stuff like that… mostly cleaning… only the tuning step used real acids. So big improvements in manufacturing: Xray measurements gone, Xray induced damage tuning gone, Raw/real rocks gone. Mostly, though, the women were not dressed up or good looking like that. Well there was this one super hot momma… a proto-cougar that was … well, that is another type of story all together.

  6. It’s astonishing how much effort was required to manufacture those crystals compared to today’s probably100% automated process using synthetic quartz. I wonder how much those crystals cost adjusted to today’s dollars? I can buy a 20Mhz crystal for $0.19 US. For an estimate, If 3 hours of hands on manufacturing time was spent on each crystal in that film (from raw material sorting to packing them up), and you say they are made today in the USA with the same process in the film at a shop rate (with overhead) of $60/hour, then these are worth roughly $180 each not including raw materials. Cool look into history. Electronics sure have gotten cheap. BTW- gotta wonder where all that chemical laden wash water was going :).

    1. Having personally lived the 70’s version of this manufacturing/technology (25 years jump into the future from the video) I would love to see today’s manufacturing process. There has been another 40 years to automate the last manual parts but I imagine the change in crystal growth is the most dramatic as we are all used to seeing robots doing the other stuff.

      The Ammonothermal Vessels we used in the 70s were about 14 feet tall and the walls of the vessels were from 10-15 inches thick aluminum. the machined plug in the top was about a foot in diameter and a foot long. The whole vessel heated up with big resistors in the walls near the bottom of the vessel inside the insulating layer. i never got to see the actual resistors so I don’t know what they used or how they were wired other than they were wired to 440 mains voltage.

      I understand that modern vessels heat the materials inside the vessel and not the vessel itself so much… allowing thinner walls and lower power consumption. I would love to see those in action sometime.

      Being in Kansas, there were tornado power outages that were a real setback to the growth process. Temp cycles of the vessels caused big problems. We had to use a crane to pull the whole vessel through the roof of the building to send to a place that could saw open the vessel. I wish I knew why the temp cycle was so bad for the vessel and why we didn’t have big enough generators or something but it was a long time ago…

  7. So these women stood in front of (I assume) dental X-ray machines for days on end with little to no shielding? I wonder how high their cancer rate is. Then to use Chromic acid I bet most of these factories are superfund sites and HF( ‘frequency etch’) *shudder*.

    1. The X-Ray exposure chamber was lead encased.

      Old design principles where not as guided by math and often an approximation was made and huge tolerance margins were applied. This is why old equipment was so reliable and lasted decades.

      Need a resistor to dissipate 1 Watt. Sure a 1 Watt resistor will do it, but for how long? Use a 5 Watt resistor and it will last forever.

  8. Crystals are somewhat sensitive to radiation damage. Natural quartz is much more sensitive than artificially grown crystals, and sensitivity can be further reduced by sweeping the crystal – heating the crystal to at least 400 °C in a hydrogen-free atmosphere in an electric field of at least 500 V/cm for at least 12 hours. Such swept crystals have a very low response to steady ionizing radiation. Some Si(IV) atoms are replaced with Al(III) impurities, each having a compensating Li+ or Na+ cation nearby. Ionization produces electron-hole pairs; the holes are trapped in the lattice near the Al atom, the resulting Li and Na atoms are loosely trapped along the Z axis; the change of the lattice near the Al atom and the corresponding elastic constant then causes a corresponding change in frequency. Sweeping removes the Li+ and Na+ ions from the lattice, reducing this effect. The Al3+ site can also trap hydrogen atoms. All crystals have a transient negative frequency shift after exposure to an X-ray pulse; the frequency then shifts gradually back; natural quartz reaches stable frequency after 10–1000 seconds, with a negative offset to pre-irradiation frequency, artificial crystals return to a frequency slightly lower or higher than pre-irradiation, swept crystals anneal virtually back to original frequency. The annealing is faster at higher temperatures. Sweeping under vacuum at higher temperatures and field strength can further reduce the crystal’s response to X-ray pulses.Series resistance of unswept crystals increases after an X-ray dose, and anneals back to a somewhat higher value for a natural quartz (requiring a corresponding gain reserve in the circuit) and back to pre-irradiation value for synthetic crystals. Series resistance of swept crystals is unaffected. Increase of series resistance degrades Q; too high increase can stop the oscillations. Neutron radiation induces frequency changes by introducing dislocations into the lattice by knocking out atoms, a single fast neutron can produce many defects; the SC and AT cut frequency increases roughly linearly with absorbed neutron dose, while the frequency of the BT cuts decreases. Neutrons also alter the temperature-frequency characteristics. Frequency change at low ionizing radiation doses is proportionally higher than for higher doses. High-intensity radiation can stop the oscillator by inducing photoconductivity in the crystal and transistors; with a swept crystal and properly designed circuit the oscillations can restart within 15 microseconds after the radiation burst. Quartz crystals with high levels of alkali metal impurities lose Q with irradiation; Q of swept artificial crystals is unaffected. Irradiation with higher doses (over 105 rad) lowers sensitivity to subsequent doses. Very low radiation doses (below 300 rad) have disproportionately higher effect, but this nonlinearity saturates at higher doses. At very high doses, the radiation response of the crystal saturates as well, due to the finite number of impurity sites that can be affected.

    1. *blink* O_O wow… during nuclear events, that can wipe out any radio equipment for a considerable period of time until the crystals settle again, assuming they get close enough back to spec to continue to work at ALL at the operating frequency. That is, also assuming their shielding didn’t protect them enough, which is hard to do in portable equipment.

    2. Your numbers seem a bit off. “high doses” are 100 rads, but “very low radiation doses” are below 300…..

      Since the military had their branch wars to see who could entrench closer to ground zero back in the 50’s they’ve probably got their radios up to snuff by now. If your radio/computer got hit w/ 300 rads and knocked out for 20 min you’re not gonna be in much better condition. In most cases getting out of there and to a med center would probably take higher priority than messing w/ electronics

  9. Thank you HaD for these Retrotacular series… I find them all very interesting and enjoyable. It is amazing to see how much different things are today (both good and bad). Plus those big knobs and dials on the old equipment are simply beautiful!

  10. These things are still good to know if some new-fangled technology that replaced an older one suddenly becomes a problem, and someone has to go back to the old way to accomplish the same thing. It also helps to inform on where we’ve come from, which can lead to unexpected innovations as well.

    1. It’s unlikely that anyone will be replacing the crystals in any devices with hand made crystals, unless it’s just for kicks. Your point about understanding current technology by reviewing legacy processes however is on the mark in my opinion.

  11. There’s an old abandoned industrial quartz quarry in the middle of nowhere on Vancouver Island. Somebody had the foresight to buy that worthless property in the 70s. Got filthy stinking rich extracting the Gold and Silver out of piled up waste rock…

    1. That is one scary incident. I would have assumed that high temperature and pressure vessels like that in a populated area would be below ground level. But maybe that would only make the explosion worse.

  12. When I was in school I made a really really crude QCM by hand lapping a piece of natural quartz into an oscillator. I made all of my spatial measurements with a petrographic microscope. That guy is in the frame with my degree along with a hand drawn 52 second geologic map with data gathered using non-electronic methods. I did the QCM as a side project while I was in the lab to see if I could, I really regret not trying to get some sort of credit on that one.

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