Pouring the 200 inch disk at Corning Glass Works(nyheritage.org)
nyheritage.org
Pouring the 200 inch disk at Corning Glass Works
https://nyheritage.org/collections/pouring-200-inch-disk-corning-glass-works
61 comments
Video of recent recoating: https://www.youtube.com/watch?v=lkBgQaJVKjc
>It seems like the first mirror cracked
Firebrick bolted to the base of the mold to form the void spaces broke loose and floated to the top of the mirror blank.
Firebrick bolted to the base of the mold to form the void spaces broke loose and floated to the top of the mirror blank.
> they spent 11.5 years polishing it down to 14.5 tons
wow, talk about a long-term project
wow, talk about a long-term project
The site says that the first mirror cracked due to breaking of the mould.
My dad worked as an engineer at Corning in the 80s and 90s. In addition to their general glass expertise (the museum is really incredible and I highly recommend it) Corning’s importance in the early days of the internet is pretty amazing and I think not as well known. They basically built all the earliest fiber optics cabling for communication networks. We lived in the town of Corning and had a fiber internet connection in our house that my dad was testing back then. They are a super cool company and I will always appreciate them as an example of one that does one thing, really well (glass) but managed to grow by finding more and more uses for their speciality.
> Corning’s importance in the early days of the internet is pretty amazing and I think not very well known
After the fiber optics, they repeated the performance with the Gorilla Glass. See, we don’t understand it anymore today but having glass screens on “smartphones” was a revolution - we didn’t do touchscreens earlier because screens were plastic, like in the Palm Pilot; they were plastic because people pushed insensitively, people did that because the touch wasn’t sensitive at all (cursor would always land at the wrong place, or not be sensed at all).
What Corning built for Apple was a glass screen, almost unbreakable, and thin enough to have an amazing touch resolution.
https://www.fastcompany.com/40493737/how-cornings-crash-proj...
After the fiber optics, they repeated the performance with the Gorilla Glass. See, we don’t understand it anymore today but having glass screens on “smartphones” was a revolution - we didn’t do touchscreens earlier because screens were plastic, like in the Palm Pilot; they were plastic because people pushed insensitively, people did that because the touch wasn’t sensitive at all (cursor would always land at the wrong place, or not be sensed at all).
What Corning built for Apple was a glass screen, almost unbreakable, and thin enough to have an amazing touch resolution.
https://www.fastcompany.com/40493737/how-cornings-crash-proj...
Having broken many smartphone screens, I have to disagree with the characterization of "almost unbreakable." Sure, the screens are tougher than, say, house glass but that doesn't make it unbreakable. The number of screen repair stores at the mall pretty much testify to the accuracy of this phrase.
In earlier smartphones fractured screens were indeed very rare, because the glass did not reach so close to the edges of the phone, i.e. to the impact zones.
My "Razr i" took a hell of a beating. The iPhone 3 was also quite robust. Galaxy S4, iPhone 4 were probably the turning point in terms of robustness vs aesthetics.
Yeah, I felt that earlier phones had more flex in the shell vs innards, which absorbed the impact; my Galaxy S2 and S5 were also famous for scattering parts all over the floor upon impact (case, battery, etc:), which was hilarious but I also felt (perhaps wrongly) it helped dissipate the energy of the impact. They also tended to have a very very tiny "lip" where the shell of the case would touch surface rather than screen if you put them upside down.
iPhone 5 was my first fragile phone. I sat on my iPhone 4 all the time, it being in my back pocket. The 5 thinned out and I warped the frame.
Before the era launched by Gorilla Glass, phones weren’t even made out of glass. So, yes, I broke several phones (Android, never iPhone despite having been less careful about those), but it’s still better glass than before.
Corning and Apple should have a glass screen on iDevices users can replace as easy as operating a laminating machine, fax machine or photocopier. They pop the iDevice in that and 60 seconds later the screen is new again.
I recall visiting the museum many years ago and seeing a demo where they heated a glass rod and pulled a fiber. This was probably when fiber optics was in its infancy. It was definitely a highlight for a young science nerd. I would love to go back some day.
Along those lines I highly recommend the episode of the show “How we Got to Now” about glass [0]. It tells the story of how clear glass was developed, something I always took for granted, but early glass was not clear and took a major effort to create. The show then goes into how Corning took it to a new level for fiber optics. The whole series is excellent and similar to James Burke’s excellent series “Connections”. [1]
[0] https://www.imdb.com/title/tt4160136/
[1] https://www.imdb.com/title/tt0078588/
[1] https://www.youtube.com/watch?v=XetplHcM7aQ&list=PLf02uWXhaG...
Along those lines I highly recommend the episode of the show “How we Got to Now” about glass [0]. It tells the story of how clear glass was developed, something I always took for granted, but early glass was not clear and took a major effort to create. The show then goes into how Corning took it to a new level for fiber optics. The whole series is excellent and similar to James Burke’s excellent series “Connections”. [1]
[0] https://www.imdb.com/title/tt4160136/
[1] https://www.imdb.com/title/tt0078588/
[1] https://www.youtube.com/watch?v=XetplHcM7aQ&list=PLf02uWXhaG...
+1 on the museum
I did some consulting for Corning back in the late 2000s and took an afternoon to visit the museum. I can't recommend it enough.
Corning is an exceptional company and so much of our technology, from fiber-optics to monitors and screens to Gorilla Glass, is thanks to the brilliant minds at work there.
I did some consulting for Corning back in the late 2000s and took an afternoon to visit the museum. I can't recommend it enough.
Corning is an exceptional company and so much of our technology, from fiber-optics to monitors and screens to Gorilla Glass, is thanks to the brilliant minds at work there.
I had a great time a while back visiting the museum with a friend who works for Corning, trying my hand at glass blowing for a couple hours, and then wandering around some of the cool places in the Corning buildings, before going to have some drinks at the appropriately named "Glory Hole" pub on Market Street, but I think that one is long gone now.
They cast the mirror in 1935, brought it to Cal Tech in 1936, finished assembling the telescope in 1939, tested and adjusted it for another ten years (they took a break to fight World War 2), and so it was not until 1949 that they got the first image out of it. Very soon the telescope would discover that the Andromeda galaxy was twice as far as we'd thought. The giant lens is still there and is still making discoveries today. It found a new mini-moon of Jupiter in 2010.
The length of time they annealed for is staggering. I believe it was continuously rotated throughout that time, to ensure even thermal and mechanical load.
I also like that they pressed on with annealing the first cast even though it was a reject. Avoid the unknown when you repeat for the final one.
There's a blog post I can't find any more about a camera nut visiting one of the last Japanese refactories capable of making lenses and the excruciating processes they go through to make complex zonally variant glass. Mirrors seem almost simple by comparison.
I also like that they pressed on with annealing the first cast even though it was a reject. Avoid the unknown when you repeat for the final one.
There's a blog post I can't find any more about a camera nut visiting one of the last Japanese refactories capable of making lenses and the excruciating processes they go through to make complex zonally variant glass. Mirrors seem almost simple by comparison.
> There's a blog post I can't find any more about a camera nut visiting one of the last Japanese refactories capable of making lenses and the excruciating processes they go through to make complex zonally variant glass.
Was it this one?
https://www.imaging-resource.com/news/2018/04/17/glass-for-g...
Was it this one?
https://www.imaging-resource.com/news/2018/04/17/glass-for-g...
Not the OP, but that was a great article - thanks.
> I also like that they pressed on with annealing the first cast even though it was a reject. Avoid the unknown when you repeat for the final one.
If only we did this for software instead of just keeping the reject.
If only we did this for software instead of just keeping the reject.
Instead, every "MVP" project I've been on has ended up as the final shipped product. Often with no further improvements at all, let alone anything the user asked for. Big Agile really has poisoned the industry.
Yes, I was struck by the length of cooling as well. A year sounds like an arbitrary period, but seems long.
I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day. Which I assume means inside an active furnace.
The additional energy, and hence cost of the finished glass but have been massive.
Presumably they learned this would be necessary from the test piece, which presumably cracked at some point.
I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day. Which I assume means inside an active furnace.
The additional energy, and hence cost of the finished glass but have been massive.
Presumably they learned this would be necessary from the test piece, which presumably cracked at some point.
> I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day.
It's relevant to remember that this is a gradient tempreture throughout the mass that declines and not a uniform fall throughout.
An analog might be to think of a porous spongy material (clay, heavy peat moss, etc) and water .. annealing is the process of slowly leaching out the tempreture (or water) with no abrupt gradient changes that lead to cracking.
As the temp. in the annealing furnace is staged down, there must be a pause to allow the heat to flow out from the mass centre to match the furnace before the next reduction.
> Which I assume means inside an active furnace.
Ideally a very well insulated furnace so that little energy input is required to maintain the desired furnace mean.
It's relevant to remember that this is a gradient tempreture throughout the mass that declines and not a uniform fall throughout.
An analog might be to think of a porous spongy material (clay, heavy peat moss, etc) and water .. annealing is the process of slowly leaching out the tempreture (or water) with no abrupt gradient changes that lead to cracking.
As the temp. in the annealing furnace is staged down, there must be a pause to allow the heat to flow out from the mass centre to match the furnace before the next reduction.
> Which I assume means inside an active furnace.
Ideally a very well insulated furnace so that little energy input is required to maintain the desired furnace mean.
And grinding and polishing away the 4½ tons of glass in the blank to make it parabolic took 14 years!
It says the mirror was installed 4 years after being made, where did you get 14 years from?
I haven't read this through thoroughly, but a lot of the final polishing must have been done after it was in place. It was only moved from Pasadena to Mount Palomar in 1947. There is both a '47 and '49 as being when figuring was done. https://sites.astro.caltech.edu/palomar/about/history.html
First Light, by Richard Preston, is well worth reading. Technical details on the Hale telescope balanced with stories of the astronomers who use it.
Two standout passages for me are the construction of the parabolic primary (by the end they were polishing it with the ball of their thumb, knowing how much glass each pass would wipe off), and the support mechanisms that account for flexing in the mirror, which sound like absolute black magic to someone trained on digital systems.
Two standout passages for me are the construction of the parabolic primary (by the end they were polishing it with the ball of their thumb, knowing how much glass each pass would wipe off), and the support mechanisms that account for flexing in the mirror, which sound like absolute black magic to someone trained on digital systems.
This is still an impressive technical achievement nearly a century later.
As another commenter has already mentioned, there really is something to be said for a business picking one thing- just a single specialty- and doing it really d**ned well.
Maybe Corning can give me some pointers on how to get a modest 3'x3' piece of glass for my coffee table back from my local home improvement store without having it shatter into a million pieces...
As another commenter has already mentioned, there really is something to be said for a business picking one thing- just a single specialty- and doing it really d**ned well.
Maybe Corning can give me some pointers on how to get a modest 3'x3' piece of glass for my coffee table back from my local home improvement store without having it shatter into a million pieces...
Maybe Corning can give me some pointers on how to get a modest 3'x3' piece of glass for my coffee table back from my local home improvement store without having it shatter into a million pieces
Simple, hire having it delivered. People who deal with decent-sized chunks of glass or other brittle materials like stone countertops have vehicles with structures built to support what's being transported safely. For a 3x3 piece, a rack in the back of a pickup truck would likely work fine, if it was a larger tabletop then a glass contractor vehicle with a larger carrying space on the side would be needed.
A thicker piece of glass might also work better.
Simple, hire having it delivered. People who deal with decent-sized chunks of glass or other brittle materials like stone countertops have vehicles with structures built to support what's being transported safely. For a 3x3 piece, a rack in the back of a pickup truck would likely work fine, if it was a larger tabletop then a glass contractor vehicle with a larger carrying space on the side would be needed.
A thicker piece of glass might also work better.
My favorite part of the story is the first attempt, which failed, but Corning continued on with it as an experiment. And that’s the one in the museum now.
That is how you accelerate learning anything. In a large multi-stage, multi-disciplinary project, there is always a temptation to give up and start over the first time a stage fails.
But that means you always enter new stages with perfect inputs and no experience. Way better to keep working on flawed WIP to build experience and test new processes with lower stakes.
That is how you accelerate learning anything. In a large multi-stage, multi-disciplinary project, there is always a temptation to give up and start over the first time a stage fails.
But that means you always enter new stages with perfect inputs and no experience. Way better to keep working on flawed WIP to build experience and test new processes with lower stakes.
What's Corning's secret? It seems they have been at the forefront of innovations in their industry for almost a hundred years. Has no one ever disrupted them with a crucial patent? Almost everything in the world changed in the past hundred years yet they're still world leader.
Among other things, that region of the country was a hot bed of innovation, with multiple companies big and small, maybe an early silicon (dioxide) valley. Polaroid, Kodak, and many smaller companies. University of Rochester was and is a top school for studying optics.
Polaroid was started in, and grew around Cambridge MA. It was kept alive on life support by a $1B settlement paid by Kodak for infringing their instant photo patents
They have some of the best minds in the world working for them. Their knowledge of glass, the physics of light, materials, and related manufacturing is unmatched.
Starting early. Like Zeiss, Bosch and others.
There's also the Lick Observatory's refracting telescope, still usable:
https://www.lickobservatory.org/explore/36-inch-lick-refract...
The lens was built in France in the 1880s and transported to San Jose. I don't know about COVID closures now, but I looked through it in the early 00's.
https://www.lickobservatory.org/explore/36-inch-lick-refract...
The lens was built in France in the 1880s and transported to San Jose. I don't know about COVID closures now, but I looked through it in the early 00's.
You can still go look through it! I went a couple months ago.
There is a book called "The perfect machine" about building this observatory.I found it very interesting since you might think it's not as hard as it is to make a piece of glass a few meters across and make it reflective.
Story of Palomar - 1948
https://m.youtube.com/watch?v=4miVqgNSRVY
https://m.youtube.com/watch?v=4miVqgNSRVY
At about the 20 minute mark, they show the Foucault testing of the mirror, and actually put a camera at the test focus, so you can see a Foucaugram of the mirror. It's of poor quality, but still. You see the donut. To anyone who was into amateur telescope making, ground their own mirror, used the Foucault test, and was as interested in mirror metrology tests as I used to be, this is absolutely fascinating.
https://www.youtube.com/watch?v=4miVqgNSRVY&t=1223s
https://www.youtube.com/watch?v=4miVqgNSRVY&t=1223s
A YEAR for annealing ! Amazing how they came up with that timeline, or if they were being overly cautious.
IANAME (Mech. Engineer) - but I'd bet it was mostly known & boring physics (rates of thermal conduction, coefficients of thermal expansion, etc.), experience with the material being used (stress-strain curves, crack propagation, and such), and some differential equations that weren't all that hard to get approximate solutions to. A lot of things like this are "If you could get an "A" on the Mech. Engin. 407 final, then you could pretty much figure it all out."
mind.blown. now I HAVE to go that observatory. I wonder if they do public tours?
Not this location, but the University of Arizona mirror lab does tours as well starting sometime next year: https://mirrorlab.arizona.edu/content/tours-tickets
They pour somewhat larger mirrors - most recent ones are 8.4 meters (330 inches) for the Giant Magellan Telescope.
They pour somewhat larger mirrors - most recent ones are 8.4 meters (330 inches) for the Giant Magellan Telescope.
They spin their glass while melting it, which generates a parabolic surface that only needs polishing/coating. It's so very rad.
I've known people who did something similar with epoxy and an LP record player, but doing it with molten glass is next-level!
Check out this process: https://tucson.com/news/local/watch-now-ua-lab-casts-mirrors...
There are some other videos shot in the pandemic--it's a bit of good fortune that safety controls against silicosis are also super effective against respiratory pathogens.
There are some other videos shot in the pandemic--it's a bit of good fortune that safety controls against silicosis are also super effective against respiratory pathogens.
These larger mirrors can also be made thinner now because their shape is actively controlled. They don't have to be as stiff as the mirror at Palomar, which was about at the upper limit for such mirrors (anything larger would sag too much retain its optical figure as the mirror was tilted.) Being thinner, these modern mirrors can be cooled more quickly.
https://sites.astro.caltech.edu/palomar/visitor/
They used to do campouts for students - it was a 6th grade trip.
Looks like it's closed for Covid for now.
They used to do campouts for students - it was a 6th grade trip.
Looks like it's closed for Covid for now.
The longer term effects of lost opportunity and science are the most saddening.
It's just been closed for tours and public events. It's not the same, but you can take a virtual tour here: https://sites.astro.caltech.edu/palomar/visitor/virtualtour....
I think when we have people going to basketball games, we can tour science facilities. It’s absurd anyone would be so terrified of covid at this point.
My guess is that it's less about being terrified of COVID and more about wanting to avoid the irrational members of the public (you've seen the videos) who are performatively careless about taking even minimal precautions at best, and an active danger to others at worst.
We don’t call every person at a basketball game “irrational” or “active dangers to others.”
It’s truly time to let covid fears subside and fade away.
I’m much more concerned with irrational people who get angry with someone not wearing a mask than I am that the person not wearing a mask would be a risk to me.
It’s truly time to let covid fears subside and fade away.
I’m much more concerned with irrational people who get angry with someone not wearing a mask than I am that the person not wearing a mask would be a risk to me.
> We don’t call every person at a basketball game “irrational” or “active dangers to others.”
Of course, and thankfully unhinged zealots are a small percentage of potential visitors. Still, my point is that it's hard to blame institutions that aren't mandated to have public access for avoiding the entire issue.
Of course, and thankfully unhinged zealots are a small percentage of potential visitors. Still, my point is that it's hard to blame institutions that aren't mandated to have public access for avoiding the entire issue.
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They do tours. I took astronomy at Palomar college.
There where these days where Corning and Gorilla was a selling feature of phones.
Video of the pouring process: https://www.youtube.com/watch?v=KdqaC8pLixY&t=15s
Transport: https://sites.astro.caltech.edu/palomar/media/slideshows/mir...
Polishing: https://sites.astro.caltech.edu/palomar/about/telescopes/ima...
Click the slideshow and press the left/right arrows to advance the slides or go back.
It seems like the first mirror cracked, so they manufactured a second mirror in Corning, New York (taking 10 months to cool it down and anneal it after it was poured), moved it across the country to Caltech in Pasadena, then they spent 11.5 years polishing it down to 14.5 tons... wow! And finally trucked it over to its current location in the Palomar Observatory in San Diego. I can't imagine being the crane operator while loading and unloading this thing.