We have tested a novel medium with an improved experimental protocol for the reconstruction of the geomagnetic field intensity during the last six millennia. The novel medium, namely copper slag, is distributed in many archaeological sites throughout the Old World and especially in the large production centers of the southern Levant. Slag deposits are the archaeological analog of volcanic glass that has proven to be exceptionally reliable for absolute paleointensity measurements of the geomagnetic field. Our experiment is based on the classic Thellier-Thellier method and combines the advantages of common Thellier-Thellier protocols; it also uses sever criteria for testing and filtering the results, in order to establish a well accepted data base that can be viewed as a reference within the enormous amount of inhomogeneous and often questionable paleointensity data. 27 sites, mainly from the regions of Feinan and Timna, have been sampled. The results of the paleomagnetic measurements has shown that slag-deposits are the best recorder for geomagnetic paleointensity studied so far, especially in comparison to other archaeomagnetic material that consist of burned clay. The new data creates a reliable and high-quality paleointensity variations curve. This curve is a key for studying the behavior of the earth magnetic field and its triggers; moreover, it is a tool for understanding phenomena that relates to the geomagnetic intensity such as shielding of cosmic radiation and creation of cosmogenic isotopes, climatic changes and variations in the biosphere. The curve can also be used as a dating tool for archaeological sites that has problematic age determination. It is suitable mainly for some of the earliest periods (Chalcolithic – Bronze) and for the sites of the desert regions, where the accepted scheme of ceramic typology is problematic. In general, we have found low geomagnetic field intensity during the 5th and 4th millennia B.C, a peak in the first half of the 1st millennium B.C. and some smaller scale fluctuations in between. Our curve agrees with some other studies, and is consistent with the interpretation that the directly measured recent decay of the geomagnetic field intensity is a fluctuation of a magnitude common in the field and not a drastic change that leads towards reversal.