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SkepticJ
2012-Sep-14, 04:51 AM
Supposing that an ancient person wanted to make a sealed time capsule, what would have been the best ways they could have done it?

The best way I've been able to think of is lost-wax casting a jar and lid out of cupronickle and after the jar is filled, sealing it closed with tar and/or molten lead (jar resting in cold water to conduct the heat away from the contents).

profloater
2012-Sep-14, 07:47 PM
they would choose a deep cave and make pictures on the walls with metal oxides which are very stable, with engraved relief to emphasise the lines, and then seal up the cave by flooding it with a rock dam, a diverted river.

cjameshuff
2012-Sep-15, 01:46 AM
Well, how ancient?

Cupronickel is unlikely: nickel wasn't even understood to be a separate metal until the 1700s, earlier nickel alloys were accidental results of natural ores. It's also major overkill. If protected from weather in a dry place, a simple lead container could last a very long time, and it's one of the first metals smelted and one of the easiest to work with. An all-lead container also avoids galvanic corrosion, and makes it somewhat less attractive to thieves, by being both low-value and difficult to move.

For the message itself, stone tablets would probably be the most durable and stable substrate available. Perhaps fill the container with sand to prevent breakage when moved and protect the tablets from temperature shocks while sealing the container.

SkepticJ
2012-Sep-15, 05:41 AM
Well, how ancient?

Cupronickel is unlikely: nickel wasn't even understood to be a separate metal until the 1700s, earlier nickel alloys were accidental results of natural ores.

Ancient Greeks, Romans, and Chinese did create cupronickle, though.

Carbon wasn't recognized as an element until when? Alchemists didn't even have a symbol for it. The ignorance didn't stop people from making steel.


It's also major overkill. If protected from weather in a dry place, a simple lead container could last a very long time, and it's one of the first metals smelted and one of the easiest to work with. An all-lead container also avoids galvanic corrosion, and makes it somewhat less attractive to thieves, by being both low-value and difficult to move.

I love overkill. Overkill rarely fails. "Good enough" fails all the time, because all eventualities cannot be forseen.

Cupronickle isn't that valuable, after all the United States makes its nickles out of it. And it's strong, so you don't need that much of it for the task. Lead is soft, if it's not thick it'll bend under its own weight. Lots of lead is valuable, and heavy weights aren't hard to move with mechanical advantage--block and tackle and windlasses are ancient. You can move thousands of pounds with a few sticks and some rope, see the Spanish and Chinese windlasses.


For the message itself, stone tablets would probably be the most durable and stable substrate available. Perhaps fill the container with sand to prevent breakage when moved and protect the tablets from temperature shocks while sealing the container.

Good ideas.

Ceramics, too, which I think of as artificial rock. We have tons of Sumerian writing because they wrote even their mundane into it.

cjameshuff
2012-Sep-15, 06:29 AM
Ancient Greeks, Romans, and Chinese did create cupronickle, though.

As an accident of natural ores that had to be imported from certain regions of China, not an alloy designed for corrosion resistance. It was a poorly understood alloy that was called "white copper" and used as a silver substitute. It didn't become widely available until the 1800s.



I love overkill. Overkill rarely fails. "Good enough" fails all the time, because all eventualities cannot be forseen.

Except that overkill in terms of using a valuable and scarce metal is likely to result in using inadequate quantities of metal. Lead is quite resistant to corrosion when kept away from alkaline water and easy to work into a durable, thick-walled box with limited metal working capabilities, and was was cheap and widely available even thousands of years ago.



Cupronickle isn't that valuable, after all the United States makes its nickles out of it. And it's strong, so you don't need that much of it for the task. Lead is soft, if it's not thick it'll bend under its own weight. Lots of lead is valuable, and heavy weights aren't hard to move with mechanical advantage--block and tackle and windlasses are ancient. You can move thousands of pounds with a few sticks and some rope, see the Spanish and Chinese windlasses.

Cupronickel was and is extremely valuable compared to lead, especially in ancient times. The US makes nickels out of it now, but we have nickel mines and copper mines the ancients wouldn't have believed, and the metal is still of higher value than the coin itself. Lead is soft, but easily durable enough for a time capsule and more likely to take mechanical insults while remaining sealed than a thin-walled cupronickel box. And my point wasn't that a lead box would be immovable, it was that it wouldn't be worth removing for its materials. A big box made out of a metal that is used for jewelry would be.



Ceramics, too, which I think of as artificial rock. We have tons of Sumerian writing because they wrote even their mundane into it.

I considered ceramics, but they'd be a bit less durable than a slab of hard, fine grained stone. Considerably easier to make into tablets with messages, though.

SkepticJ
2012-Sep-15, 07:14 AM
Tar could protect lead from alkaline water, couldn't it?

As long as tar isn't exposed to the sun it seems to last basically indefinitely. Anthropogenic plant-derived tar dates back over ten thousand years. Ten thousand years buried in wet dirt.

novaderrik
2012-Sep-15, 01:58 PM
don't do what they did in Tulsa, OK when they put a shiny new 1957 Belvedere in a concrete "time capsule".. it didn't work out like they had planned..

http://www.allpar.com/history/auto-shows/time-capsule.html

SkepticJ
2012-Sep-15, 02:27 PM
I wonder what they were thinking, normal concrete is porous.

It doesn't look like the plastic sheet actually surrounded the car, but was just draped over it like a dust cloth for furniture. If it had been a hermetic bag, the car would have probably been okay even resting in a pool of water.

HenrikOlsen
2012-Sep-15, 04:09 PM
And remember to make sure the items inside doesn't decompose over time. Just think cellulose acetate film stock.

cjameshuff
2012-Sep-15, 04:11 PM
Tar could protect lead from alkaline water, couldn't it?

As long as tar isn't exposed to the sun it seems to last basically indefinitely. Anthropogenic plant-derived tar dates back over ten thousand years. Ten thousand years buried in wet dirt.

It might, if protected from oxygen, and if it itself doesn't have a more corrosive influence. I think you're better off with just lead. There's a lot of lead ingots and pipes left around from Roman times that haven't suffered greatly...after 2000 years, a stable layer of oxides and carbonates, and well-preserved lettering and identifying marks stamped into them.



I wonder what they were thinking, normal concrete is porous.

There was also mud outside up to the top, and the lid looks like it was just resting on top without even an attempt at a seal, so water could just seep in and get trapped inside. Putting cans of beer in the vehicle was pretty dumb too...even without immersion in water from outside, canned drinks can corrode their cans in storage (the protective coatings aren't perfect). I can't even call this a time capsule, they just buried a car. The only protective measures they took were for show.

Concrete could work under some conditions, Pompeii and Herculaneum were fairly well preserved due to burial by Vesuvius in volcanic ash and pumice that formed a sort of natural concrete. Human remains decayed, but many frescoes, structures, and stone/ceramic items were preserved quite well.

SkepticJ
2012-Sep-15, 07:54 PM
It might, if protected from oxygen . . .

Why oxygen? Fire?

cjameshuff
2012-Sep-15, 08:03 PM
Why oxygen? Fire?

Just slow chemical and microbial degradation.

Romanus
2012-Sep-16, 03:02 AM
I'm a fan of just plain old glazed ceramics--an amphora with a ceramic stopper and sealed with bitumen, preferably buried in a remote desert location (but not so remote that no one will stumble across it, ever).

SkepticJ
2012-Sep-16, 03:23 AM
Just slow chemical and microbial degradation.

I'm doubtful that this happens to a meaningful degree.

If lumps* of birch bark tar survive with teeth and finger print marks intact from 10K years ago buried in never-dry Northern European soil, what does it take to break it down?

Copal and amber don't break down in tropical rainforest soil.

*With volatile chemicals kept entrained in their cores.

SkepticJ
2012-Sep-16, 03:29 AM
I'm a fan of just plain old glazed ceramics--an amphora with a ceramic stopper and sealed with bitumen, preferably buried in a remote desert location (but not so remote that no one will stumble across it, ever).

Stoneware and porcelain are really good for this. They're non-porous and as such don't require glazing, though they typically are for aesthetic reasons.

Only China had the tech to fire them in ancient times.

Ara Pacis
2012-Sep-16, 06:41 AM
Stoneware and porcelain are really good for this. They're non-porous and as such don't require glazing, though they typically are for aesthetic reasons.

Only China had the tech to fire them in ancient times.

Do you mean glazing or fired clay in general?

A time capsule might use a thick glass. Borosilicate might be good, but maybe any glass might work if made thick enough.

HenrikOlsen
2012-Sep-16, 09:25 AM
Do you mean glazing or fired clay in general?

Stoneware and porcelain require considerably hotter firing so when looking at which cultures could make them, they can be considered different tech from fired clay which can be done in a simple fire.

cjameshuff
2012-Sep-16, 02:55 PM
I'm doubtful that this happens to a meaningful degree.

If lumps* of birch bark tar survive with teeth and finger print marks intact from 10K years ago buried in never-dry Northern European soil, what does it take to break it down?

Copal and amber don't break down in tropical rainforest soil.

In the overwhelming majority of cases, yes they do. It takes unusual conditions to preserve them. That's why they're rare. Amber and copal formation requires rapid, deep burial in sediments, otherwise the material just decays away. If this weren't the case, forests would quickly become choked in resin accumulations.

Most surviving remains of things like birch tar are recovered from places like bogs that quickly bury objects in a sterile, oxygen-poor environment, or from extremely cold and dry environments of the sort that also naturally mummify human remains. The vast majority of artifacts were less well protected and quickly decayed.

SkepticJ
2012-Sep-16, 05:30 PM
Do you mean glazing or fired clay in general?

A time capsule might use a thick glass. Borosilicate might be good, but maybe any glass might work if made thick enough.

They didn't have borosilicate glass in ancient times.

If glass isn't made just right, when exposed to water it develops something called glass disease. That's why Roman glass looks foggy sometimes.

Ara Pacis
2012-Sep-16, 05:41 PM
They didn't have borosilicate glass in ancient times.

If glass isn't made just right, when exposed to water it develops something called glass disease. That's why Roman glass looks foggy sometimes.

That explains why my crackle votives keep developing this weird grease-like coating on it.

SkepticJ
2012-Sep-16, 06:04 PM
In the overwhelming majority of cases, yes they do. It takes unusual conditions to preserve them. That's why they're rare. Amber and copal formation requires rapid, deep burial in sediments, otherwise the material just decays away. If this weren't the case, forests would quickly become choked in resin accumulations.

Most surviving remains of things like birch tar are recovered from places like bogs that quickly bury objects in a sterile, oxygen-poor environment, or from extremely cold and dry environments of the sort that also naturally mummify human remains. The vast majority of artifacts were less well protected and quickly decayed.

Copal isn't that rare. Well, it wasn't before people burned it as fuel and used it up in rituals. Amber's not that rare either, pretty amber is. Most of it is foggy with air bubbles, has mundane trash stuck in it, etc. "Trash amber" is used to make varnishes, and other things. Not precious at all.

I may be wrong about this, but wouldn't the fact that resin is highly flammable neatly explain why it needs to be buried to survive, not because microorganisms can eat it on long time scales?

I concede you may be right about this, though. However, you're not right about birch bark tar. It survives in quite normal, wet, oxygenated soil, just feet under the ground (under modern towns) on Roman pottery in England.

cjameshuff
2012-Sep-16, 07:03 PM
Copal isn't that rare. Well, it wasn't before people burned it as fuel and used it up in rituals. Amber's not that rare either, pretty amber is. Most of it is foggy with air bubbles, has mundane trash stuck in it, etc.

Compared to the plant resins it's formed from, it is rare. Not just pretty stuff, any of it. If it didn't decompose most of the time, there'd be huge quantities of it around, fires or not.



I may be wrong about this, but wouldn't the fact that resin is highly flammable neatly explain why it needs to be buried to survive, not because microorganisms can eat it on long time scales?

Nope. It'll rot away along with the trees that formed it without any fires being involved. Wildfires don't regularly happen everywhere, and even where they do happen, shallow burial would be enough protection...tree root systems go more than deep enough. The resins resist decomposition more than most other materials, but are far from impervious to decay.



I concede you may be right about this, though. However, you're not right about birch bark tar. It survives in quite normal, wet, oxygenated soil, just feet under the ground (under modern towns) on Roman pottery in England.

Examples? Of tar seals or repairs that have survived in good condition after shallow burial, that were not recovered from boggy ground, which as I've already mentioned is notable for being anoxic and sterile?

Once again, this stuff was very widely used, in pottery, brick bathtubs, roofs, boats, mats, baskets, plumbing, etc. If it didn't decay, there'd be bits of tar-covered garbage everywhere. Instead, there's scattered archeological finds where pieces ended up in conditions that preserved them.

SkepticJ
2012-Sep-16, 08:14 PM
Nope. It'll rot away along with the trees that formed it without any fires being involved. Wildfires don't regularly happen everywhere, and even where they do happen, shallow burial would be enough protection...tree root systems go more than deep enough.

Wildfires do or did happen regularly (every few decades should be enough, right?) where conifers grow or grew in abundance. Before people were around to put them out, wildfires went until there was no more fuel on the ground.

Wood rots. Anyway, haven't you ever seen a conifer stump fire? The fire follows the roots down into the ground, the burned-out voids of where the roots were giving oxygen flow deeper and deeper, the fire getting slower and slower with depth/restricted oxygen flow. Fire can smoulder for years.


Examples? Of tar seals or repairs that have survived in good condition after shallow burial, that were not recovered from boggy ground, which as I've already mentioned is notable for being anoxic and sterile?

Example. (https://docs.google.com/viewer?a=v&q=cache:DUz4ISh-4oQJ:www.mecon.nomadit.co.uk/pub/conference_epaper_download.php5?PaperID%3D5919%26M IMEType%3Dapplication/pdf+what+did+the+apocrypha+know&hl=en&gl=us&pid=bl&srcid=ADGEESgxRUYFKuHWl6gGKE19gQLzTSxX04a7Llw6s5XH 910xrW9yo5JUl0fH7IFdQBNPY1XaBfdRjiu9GIJ7Ju8d2nhR6o QTKU5ZJWTB2AOn09DT-Ppnxu_N4t5zYppmHpeBsgVa1Dhm&sig=AHIEtbStouR6kIx2hBlYKOQSeRXXH4betw)

cjameshuff
2012-Sep-16, 09:33 PM
Wildfires do or did happen regularly (every few decades should be enough, right?) where conifers grow or grew in abundance. Before people were around to put them out, wildfires went until there was no more fuel on the ground.

Not where it was too wet. They were a natural cycle in many places, but not universal.



Wood rots.

Yes, it does. Along with the pockets and other accumulations of resin, if they aren't quickly buried and preserved.



Anyway, haven't you ever seen a conifer stump fire? The fire follows the roots down into the ground, the burned-out voids of where the roots were giving oxygen flow deeper and deeper, the fire getting slower and slower with depth/restricted oxygen flow. Fire can smoulder for years.

That can happen, but often doesn't. Wildfires in fact tend to leave largely-unburned standing trunks, and generally do not burn out everything below the ground.



Example. (https://docs.google.com/viewer?a=v&q=cache:DUz4ISh-4oQJ:www.mecon.nomadit.co.uk/pub/conference_epaper_download.php5?PaperID%3D5919%26M IMEType%3Dapplication/pdf+what+did+the+apocrypha+know&hl=en&gl=us&pid=bl&srcid=ADGEESgxRUYFKuHWl6gGKE19gQLzTSxX04a7Llw6s5XH 910xrW9yo5JUl0fH7IFdQBNPY1XaBfdRjiu9GIJ7Ju8d2nhR6o QTKU5ZJWTB2AOn09DT-Ppnxu_N4t5zYppmHpeBsgVa1Dhm&sig=AHIEtbStouR6kIx2hBlYKOQSeRXXH4betw)

That's pottery fragments with traces of tar having been used as glue, and few details of the location. Highly degraded traces, often reduced to a fragmentary surface patina. This is not what I would consider a good argument for use of tar to seal a time capsule.

SkepticJ
2012-Sep-16, 11:38 PM
That's pottery fragments with traces of tar having been used as glue, and few details of the location. Highly degraded traces, often reduced to a fragmentary surface patina. This is not what I would consider a good argument for use of tar to seal a time capsule.

How could they have been more specific about the location without giving the soil pH? They give the names of the places and maps. You can look on Google Earth. It's not an anoxic peat bog.

The highly degraded traces are on jars that were exposed to high heat while used as bread ovens. Birch tar does dehydrate and lose its volatiles at such heat, becoming brittle and flaky. I should know, I've distilled some on several occasions and over-cooked it once.

Please note the intact nature of the glue on the bottom-most jar, as well as the in-text assertion that much of the pottery repairs have remained intact. For two thousand years in England, one of the dankest places on Earth.

Bitumen is the best option, but it wasn't easy to come by in many places in the ancient world.