Question about weathering of materials over time

I’m writing a story, and ran into this not-so-minor issue – trying to get a back-of-the-envelope calculation on how long it would take various items in a ghost city to age, and what the results would look like.

The city’s set in a semi-arid environment, so there has been absolutely zip in the way of precipitation. Hot and dry should be good for preservation in some ways, right?

  • Paper – how long does it take until paper that’s been kept in a dark office will reach a condition where the illuminated illustrations are still decipherable, but the paper itself will crumble into dust if touched or breathed on? That is, if such a state is achievable. Several hundred years? Closer to a thousand?

Let’s say that we have a figure on that length of time… what would the other materials listed below look like given the same amount of time?

  • Stone – assume some type of limestone, nothing so hard as marble. How much would the stone have weathered appreciably inside buildings with naked walls? Not at all? Top layer crumbling to the touch?

  • Bone – What would a skull that’d been hanging outside in the heat and so on look like? Would it have crumbled long before, or would it still be intact? It would’ve been exposed to sun, but no scavengers.

  • Dried beans in clay jars. Bean-flavored dust (yum!) or would they still be edible after a good soaking? The jars would have been stoppered and further sealed with a good slathering of wax, so hopefully the conditions would’ve been a bit more airtight.

Hope some of the more knowledgeable Dopers can help out with these details – my google-fu is not helpful.

Merci, gracias, etc!

Even with a hot and arid climate, you are going to have to worry about air pollution. I’ve read that it is a major problem for the preservation of ancient buildings in many countries.

Depends on the type of paper; wood-pulp paper produces/contains acids that cause it to turn yellow and brittle and eventually crumble; cotton rag paper would be a lot more durable. Paper kept in tight stacks or books will also survive better than single sheets exposed to the air. In cool, dark, dry conditions, good paper could last for a couple of thousand years at least.

Inside buildings, it wouldn’t weather noticeably at all; consider; there’s still intact lime plaster and paint on the inside of some Egyptian tombs.

even in an arid environment there will be dew or moisture at night time and the cycles of heating/cooling and wetting/drying will take their toll; a few hundred years possibly (consider also erosion from windborne dust and sand).

Sealing them up in completely airtight conditions might not be optimum; even apparently dry seeds contain some moisture and if this is expelled by a change in temperature, decay could happen quite rapidly in a completely sealed container.
A porous container such as an unglazed terracotta pot (still sealed completely at the top, if you like), stored in dry, dark conditions, could preserve dried seeds more or less indefinitely; multiple thousands of years would not be at all unreasonable.

Don’t forget fire; if this is an abandoned modern city, complete with all furnishings etc, sooner or later, a fire will start somewhere.
With no fire brigade to control it, the buildings affected (probably whole blocks) will be very thorougly destroyed.

**Mangetout ** – thanks for the assistance! That’s really helpful, although the city isn’t a modern one, so there wouldn’t be much to catch fire. Excellent point about the Egyptian tombs, I should’ve remembered that. :smack:

Since you brought up stone, how long would it take before the jars turned fragile and/or tile would break underfoot?

DECAY. That was the important word! My google-fu thanks you!

In the museum in which I work, we have a manuscript almost 900 years old. It looks like it was written yesterday, even though it has only been stored in a humidity/temperature controlled vault for the last ten years.

Modern books and papers, though, don’t stand a chance. They’re chock full of what we in the museum indursty charmingly call “inherent vice.” Not only with the paper self-destruct from its own acids, but the ink itself is acidic, and the glues are attrocious. Your character would probably only find the books written pre-1900 to be in readable condition. However, insects love books and so does mold.

Plastic will crumble/melt/corrode away. Not leaving no traces, mind, but any object made of plastic would probably be too brittle to be usable. Video tapes, CDs and the like would be useless.

Cloth won’t stand up too well in an area that has changing humidity. Polyester and other synthetics (as well as silk) crumbles into dust. Cotton and wool become meals for insects. The dyes used in many modern cloths are acidic, so they’ll eat away at it over time. Body soil and any organic matter that’s been spilled on it is another issue. A lot of our gowns from the 1800s have no armpits-- they crumbled away because of residual sweat in the cloth.

Glass would be virtually unchanged.

Metal exposed to rain would rust away for the most part, but might still be intact enough for you to be able to recognize what the object once was. I’ve seen rifles which have been buried in temperate climates which were completely encrusted but you could still tell what they were.

Unprotected wood fares badly. Not only is it yummy to bugs, but it can be destroyed by both humid and arid conditions. Humidity makes it expand, which basically splinters it, and arid conditions dry it out so that it crumbles.

You’ve got to be lucky in your ink though, the use of iron gall ink through most of the middle ages and renaissance has resulted in the loss of countless documents. Something like 60% of Leonardo DaVinci’s documents have been lost to transition metal catalysed corrosion, and that was in less than 600 years.