I'm not familiar enough with the discussion around this inscription to know what evidence supports the conclusion that the inscription's a fake. These findings appear to directly counter the main components of Y. Goren's argument. Personally, I don't have a stake either way. If the evidence supports its authenticity, that's great. I'm always happy to add to our corpus of Ancient Hebrew inscriptions. On the other hand, a spectre of doubt will likely always hang over this inscription.
Here's an excerpt from the article:
Our team of scientists spent some time examining the Jehoash Inscription tablet (JI) from the point of view of hard science (Ilani et al., 2002; 2008). Our goal was to determine, based solely on scientific evidence, whether the tablet is a forgery or
genuine. Since this tablet represents the only Judahite royal inscription found to date, it is of critical importance to history and Biblical Archaeology. The tablet is engraved with an inscription in ancient Hebrew that commemorates the renovation of the First Temple carried out by King Jehoash (9th century B.C.E. = 2800 years BP). A similar account of the Temple repairs is also found in Kings II: 12.
Analyses of the tablet's epigraphy and philology to date have proven to be inconclusive as to its authenticity (Ilani et al., 2002; 2008). Chemical, geologic and petrographic analyses support the antiquity of the patina, which in turn, strengthens the contention that the inscription is authentic.
The patina on the surface carrying the inscription is composed of elements derived from the tablet itself (e.g., quartz and feldspar grains) as well as from the environment (dolomite, limestone, carbon ash particles, and gold globules). The patina on the back of the tablet has the same composition but with some silica and
carbonate in one place (about 2.5 cm in diameter) near the top of the tablet. This siliceous-carbonate material could be an original vein filling within a bedding plane or a joint in the original rock, similar to those found in the clastic rocks exposed in southern Israel and Sinai, and may represent a natural rock fissure along which the rock was detached for further processing as is the case in many quarries. Thus, the remnants of a vein were thought to be the "real" patina by Goren et al., (2004). The fact that it does not appear on the inscription surface was proof that the inscription was forged.
Moreover, Goren et al., (2004) suggest that the patina on the inscribed face of the
tablet is too soft to be regarded as genuine. However, we propose that the softness or hardness of the patina cannot be used as an indicator of authenticity, especially as we reported that the light patina had been exposed to cleaning. But the biogenic black-reddish patina with the pitting made by microorganisms is firmly connected to the stone (Figs. 2-3).
The suggestion by Goren et al., (2004, p. 14) that "heated water was used to harden and ensure good adhesion of the patina" seems to us unfounded.
No indications of adhesive materials or other artificial substances that could indicate addition, pasting, or dispersion of artificial patina on the inscribed face of the tablet have been observed.
Exposures of Cretaceous marine carbonate rocks are abundant in Jerusalem and provide a majority of its building stone. Indeed, well preserved marine carbonate microfossils that were found within the patina were derived from the weathering of these exposed rocks as well as by wind transport. These minute fossils occur in abundance in everyday dust in Jerusalem (Ehrenberg, 1860; Ganor, 1975) as well as in the local soils. But, Goren et al., (2004) claimed that their finding of foraminifera
(microfossils) within the patina of the engraved surface of the JI tablet is a proof of a fake patina. We maintain that these microfossils within the patina can be easily explained as a component of a genuine patina derived from the surrounding Cretaceous marine carbonate rocks that are ubiquitous in the Judean Mountains. Indeed, their absence within a patina purportedly coming from the Jerusalem area
would be suspicious since the entire city is situated upon these marine rock exposures. These microfossils should be as plentiful in the historical past as they are today. We therefore strongly disagree that these microfossils are an indication of forgery.
Goren et al, (2004) claimed that the engraved marks of the letters are fresh. They
said that signs of fresh cuttings and polishing are exposed within the letters. Fresh engraving can be easily revealed by illuminating the tablet with ultraviolet light (Newman, 1990). However, when the tablet was illuminated with ultraviolet light, there was no characteristic fluorescence indicative of fresh engraving scars.
In addition, the biogenic black to reddish patina is covering and firmly attached to the letters with morphological continuity to the tablet surface (Figs. 2, 3 and 6).
Based upon the results of four oxygen isotopic analyses of the carbonate patina, Goren et al., (2004) concluded that the tablet must be a fake. Yet, of the four samples only two can be related to carbonate precipitation from fresh water. The two enriched ("heavy") delta O18 (capital O is the chemistry symbol of oxygen; delta O18 is the measured ratio of the O18/O16 isotopes of the oxygen) values (-1.7 per thousand and –0.9 per thousand PDB) of the patina carbonate presented by Goren et al. (2004) can be attributed to the predominance of a marine carbonate component (upon which Jerusalem sits and its building stone is made). The conclusion that the patina must be a fake is thus drawn upon the basis of the only two depleted delta O18 patina analyses which they compared to the delta O18 values preserved in dated stalagmite caves in the Jerusalem area (Goren et al., 2004, p. 7 and Fig. 9). They
concluded that the delta O18 values of the carbonate patina are too depleted to have been derived from natural meteoric water of the region and therefore claimed evidence of fraud. However, there are ways that isotopically depleted carbonate can be generated and incorporated into a genuine patina. One example is a thermal event. It has recently been brought to our attention that an isotopic study of white
crusts that cover limestones that had been burned during the destruction of the Second Temple at 70 C.E. show depleted delta O18 PDB values (-10.7 per thousand
-13.4 per thousand) (Dr. A. Shimron, personal communication, 2004). Therefore such isotopic depleted carbonate values are found in the Jerusalem area.
So, what should we make of this study? To me, it seems the Jehoash inscription is more likely authentic than fake, but as I said, I haven't been following this controversy. I know one person who has, but he has yet to get back to me on why he concluded it was a fake. Maybe he's just a big Yuval Goren fan.