The Science of Metal Detection
A Brief History
Gerhard Fisher discovered, during testing of his radio direction finder, that his device's signals were distorted in the presence of iron. Further experimentation led him to acquire the first patent for a metal detector in 1925. A similar invention, patented by Shirl Herr in 1928, was used by Benito Mussolini to recover artifacts from Italian Emperor Caligula's treasure galleons and by Admiral Byrd's second Antarctic exploration. During WWII, Polish Lt. Jozef Stanislaw Kosacki refined the technology for use as a mine detector. Finally, modern development was perfected by Charles Garrett of Garland, Texas in the 1950s.
There are 3 primary detection technologies used in metal detection: Very Low Frequency, Pulse Induction, and Beat-Frequency Oscillation. Digging History members use the Garrett AT Pro, a VLF detector.
The popular website HowStuffWorks.com has a remarkably simple guide that explains metal detection technology in all three of its forms, complete with animated imagery. You can view the guides here: VLF, PI, BFO.
The Digging History Process
Please remember that we are NOT
professional archaeologists! While our methods are not considered to
be up to their standards, we do have a system for recovery and
collection that suffices to maintain some degree of archaeological
context. However, unlike archaeologists, we do not assert that every item recovered at a site has historical significance.
Artifacts found on sites explored or surveyed by Digging History with the express purpose of historic research will be photographed, gridded, and documented for future research.
All artifacts dug or procured by Digging History with the intent to donate will be cleaned and preserved prior to donation; there is a possibility that we may mount the artifact as well, if such display would assist historical context or the recipient's ability to display it.
NOTE: Due to the nature of our artifact recovery methods, the following suggestions are recommended:
- Wait until after a rainstorm before mowing your grass! An alternative is to hose down the area. Small animals and lawnmowers are known to re-unearth "plugs" despite our best efforts to fill and tamp the holes we dig.
- The grass will grow back! We make every effort to maintain the grass root system so that unearthed grass will continue to grow after the hole is filled. Sometimes it takes some water (rain or from a hose) to encourage the grass to recuperate. If the grass at a dig site does not recover after a reasonable period, Digging History will re-seed the area at no cost to the property owner.
- Walk with care in surveyed areas! It is Digging History policy to not re-inter dug items, but also to remove all scrap and garbage from surveyed sites. Due to this, some re-filled holes may leave a depression if a larger object was removed.