[EvaH (OP)]

Colin asks:

The age of bricks can apparently be determined by the orientation of magnetic particles frozen when they went in the kiln. The deviation between true North and magnetic North changes over time and its value over time is known. As I understand it, this is used to calculate the age of the brick. My question is a) how can the direction of true North (at the time) in relation to the bricks, be determined? And b) how can the orientation of the bricks (at the time) be determined? Like a frozen compass mapped to true North will show you the deviation but if you pick it up surely the deviation is lost?

Can you help?

[evan_au]

As you suggest, bricks may be baked in a kiln in one orientation, used to build a wall in a different orientation, and if the wall falls down, land in a third orientation.

However, magnetism may be used to date lava flows, since lava is poured in one location, and remains there until a geologist picks up the rock sample (and records the orientation).

Another technique that may be used to date bricks & ceramics is thermoluminescent dating. The thermoluminescent clock is reset when the brick is fired.
See: https://en.wikipedia.org/wiki/Thermoluminescence_dating

[Bored chemist]

If you measure the magnetism of the brick-maker's furnace...

[alancalverd]

Look at the date of the building. Bricks are a fast-moving commodity and rarely more than 2 years old when first laid.

If the bricks have been re-used, Evan's suggestion of thermoluminescent dating will give you an age estimate ±10% unless the previous building was damaged by fire.

[Bored chemist]

Look at the date of the building.

very droll.

[alancalverd]

It's a consequence of the Pisa joke:

3 usual suspects want to know the height of the Leaning Tower. They have a barometer.

Pilot carries the barometer up the stairs and estimates 30 ft per millibar

Engineer drops the barometer from the top, waits for the crash, and estimates g = 32 ft/sec²

Steward asks the bloke in the ticket office.

[Bored chemist]

You forgot the mathematician who measures the height of the barometer and the length of its shadow, then measures the length of the shadow of the tower + uses the ratio   to find the height of the tower.
And the fisherman who lowers the barometer on a line from the top, then measures the line.


In the version I heard, they steward offers the ticket seller the barometer if they tell them how high the tower is.

Me; I'd just look for the sign telling people about the tower in a dozen languages.

[Salik Imran]

Hello,
All of you forgot to mention one of the most common methods most scientists/archaeologists use; Carbon dating(or radiocarbon dating.) They use it for fossils and ruins millions of years old but I a  not sure if it work =s for more recently produced artefacts.
Yours sincerely,
Salik Imran.

[Bored chemist]

Hello,
All of you forgot to mention one of the most common methods most scientists/archaeologists use; Carbon dating(or radiocarbon dating.) They use it for fossils and ruins millions of years old but I a  not sure if it work =s for more recently produced artefacts.
Yours sincerely,
Salik Imran.

Radiocarbon dating only works well for things that were alive.That excludes bricks.
It also only works for items younger than about 60,000 or 70,000 years old.

[Salik Imran]

ok. Thanks for clarifying.