Announcement

Collapse
No announcement yet.

Metalcasting,science,etc type question.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Metalcasting,science,etc type question.

    Tonight on Nova,they had the story of some artifacts found in Isreal dating to the first century A.D.
    Among these was a bronze incense ash shovel.The archeologist doing the research needed to date the shovel,but they made the statement that "since there is no way to date the metal in the shovel,he will have to use carbon dating on the rope recoverd in the same find".

    This got me wondering,if fired pottery can record the intensity of Earth's magnetic field at the time it cooled and if atmospheric composition is recorded in tiny bubbles of gas trapped in ice found in sea floor sediment,shouldn't it be possible to date a piece of cast metal at least in rough limits?
    I just need one more tool,just one!

  • #2
    Go on. Just how so? You must have some idea in mind.
    Free software for calculating bolt circles and similar: Click Here

    Comment


    • #3
      Well it would seem that if the pottery is affected by the magnetic field at the time of firing,wouldn't it be reasonable to assume the same would be true of a bronze casting?
      The method maybe would not be very accurate as the field strength doesn't fluctuate but by a factor of 2-4% over a decade,but if organic matter were not present with the artifact being dated it surely would be better than nothing.Assuming of course a reasonably accurate sampling of pottery or shards from known time periods were used for a reference lot.
      I just need one more tool,just one!

      Comment


      • #4
        One problem would be...they would have to test to destruction a piece of the artifact and they are hesitant about doing that

        Walt
        Walt

        Comment


        • #5
          There are two ways to get a date on metal items. One is to look for radioactive decay of some component of the metal. Unfortunately the isotopes involved have half lives way too long to get a useful measure. The other is to measure oxidation film thickness into the metal pores, but that is affected by the environment in which it was buried and the soil moisture and oxygen concentrations. The oxidation film won't give a date other than to confirm it isn't a contemporary fake.

          The half life of carbon found in the rope vegetable fiber is probably the best way to get a reasonably accurate date as long as the archaeologists can confirm somehow that the rope and the casting were made in the same time period.

          I recently read a book on the shroud of Turin and was surprised to find out that the chemical washes used for a carbon 14 test can really goof up the results. Petrochemical based cleaners turn out to show an unmeasurably old age.

          Comment


          • #6
            Iron can be approximately dated based on chemical composition which shows what process was used to refine it. We have a good idea what processes were in use where and when. Bronze can be geographically located by isotope ratios that are unique to certain areas but that doesn't rule out the use of imported scrap. As for magnetic field entrapment it doesn't mean much. For any magnetic material the field can be altered by even mild impact.
            Free software for calculating bolt circles and similar: Click Here

            Comment


            • #7
              Evan:

              Well, not entirely true. We can have an educated guess at it - and we might be right. Modern metalurgists still cannot make steel as good as ancient Japanese Sword Steel. Even modern day Japanese masters that have the passed on knowledge of their forefathers make inferior metal. So very sad for us - a lost art.

              Comment


              • #8
                Thrud, testing of the ancient swords was done on captives and "useless" people.

                Hmm.. maybe we don't need them that much?

                Amazing how many japanese family heirlooms got brought back to the USA as souviniers. They put a plain handle on them and took them to battle. I had one, a carved legbone for a handle.. Sold it in a moment of sheer stupidity.

                David

                Comment

                Working...
                X