Forgotten knowledge, methods, technology, etc.

Inspired by this thread:

Civilizations come and go, and often knowledge comes and goes with them. What was the most important knowledge or advanced methods or technology that a civilization ever forgot?

It may not be the most important thing anyone’s ever forgotten, but it still amazes me that despite all the efforts of the Impossible Project, nobody has been able to recreate good instant film after Polaroid stopped making it.

I believe they’ve solved the issue of Damascus Steel, and Egyptian Bronzes. But everything I’ve read still seems to be pretty vague about the actual nature of “Greek Fire”

Even Adrienne Mayor’s book is pretty vague on the topic.

Civilisations or cultures?

Civilisations generally find it harder to lose technology because they generally have writing and they are also generally in contact with other civilisations. So it takes quit a lot for a civilisation to lose technology. Parts of the Roman Empire during the dark ages saw a massive reduction in their engineering ability, for example, and lost the ability to make large stone buildings, but that’s about the most extreme I can think of.

Cultures, OTOH, can lose almost anything. Cultures have lost the ability to make fire, that’s pretty damn significant…

That’s just a subjective judgement. Many people, including IP itself, will tell you that their Polaroid replacements are identical to the original, and that their new products are superior. IP even uses the same factory as Polaroid uses.

IOW the technology is no more lost than the tehcnology needed to make a 1963 Oldmobile.

Roman concrete.

Its weaker but longer lasting than modern concrete. Its use disappeared during the middle ages and we are only just in the last decades working out the exact methods to recreate it.

Maybe they’ve made big improvements in the few months, but the last time I saw any of Impossible’s film, the end results were washed out and blotchy. They admit it’s not as good as we were used to, and user reviews on Amazon agree.

For the time being, the precise technology, chemistry and process needed to make a good replica of Polaroid film has been lost. There’s nothing at all “superior” about Impossible’s efforts if they admit to the color and contrast issues and make multiple warnings about how the photos must be immediately shielded from light, kept warm and not shaken for at least three minutes, whereas the original was good to go as soon as it popped out of the camera, and shaking did nothing but stir a small breeze.

Has it in fact been truly lost - that is, no one alive knows exactly how to do it, and all written records of how to do it have been destroyed? Or does the Polaroid company still have detailed documents about the ingredients and process, but they’ve chosen not to reveal them to anyone else?

The Antikythera mechanism? http://en.wikipedia.org/wiki/Antikythera_mechanism

Well, the ancient Greeks forgot how to write, which is why they went from Linear B to the Greek alphabet some centuries later.

Sometimes it is not what has been forgotten, but what was not known in the first place.
FOGBANK is a foam material used in thermonuclear warheads. Production was stopped in 1989, and production lines decommissioned. When a warhead refurbishment program was instituted in 2000, production of FOGBANK was restarted. It took until 2009 for useful material to be produced. Not only were records and details lost, modern raw materials were much more refined than original feedstocks, and a contaminant in the original raw material proved to have a vital role in the correct production of FOGBANK material.

It took 11 years for that knowledge to be lost, and 9 years to be recovered.

Si

As I understand it, during the Greek Dark Ages, there was no written Greek and apparently no one understood the writing system that had formerly been used:

http://en.wikipedia.org/wiki/Greek_Dark_Ages

However, I’m not an expert on this, so please correct me if I’m wrong.

Dr. Drake and I had simul-posts there.

Sounds like the problem Dr. Jeckyll had with his ingredients.

I’ve been told that the actual formula for the beautiful stained glass used in the great cathedrals in Europe is lost. No cite, I could be wrong.

Is seemed to remember a discussion–it happened here! All those brains couldn’t come up with any actual “lost” stained glass techniques.

Washington DC’s National Cathedral is full of stained glass–& it was begun in the 20th century…

Have a look at this book, Theophilus’ On Divers Arts – it’s a contemporary book telling you how to make stained glass (and lots of other stuff) – the one I referred to in the previous thread
http://www.amazon.com/Divers-Arts-Dover-Art-Instruction/dp/0486237842

I need to ask, do you mean the technology to perform a task. Or a specific way of doing so. many of the things, Roman Concrete, Greeks fire or Damascus steel are not strictly speaking list, we have things which do their job better in many ways. What we have lost is the specific way that was made.

Go read post number 239. It’s even happened right here on the Dope!

http://boards.straightdope.com/sdmb/showthread.php?t=655746&page=5

The ancient Bolivians:http://en.wikipedia.org/wiki/File:Zonnepoort_tiwanaku.jpg
seem to have been able to finish cut stone to an extraordinary degree of flatness. I have never seen an explanation of how this was done (with only stone tools)
Later structures (Inca fitted blocks) are impressively worked, but nothing like what is seen at Tiwanaku.
How did they do it?

I read something to the effect of, if you move the stone back and forth in place, it naturally smooths away any imperfections in fit.