There are many websites and blogs discussing all manner of interesting things about the Qeiyafa ostracon. I have hesitated to add to the
However, I would like to point you to an article (available as a PDF for download here) which details the science behind the imaging of the ostracon. I find this fascinating (and a great change of pace from the speculation contained in some of the other articles).
The article is SPECTRAL IMAGING OF OSTRACA by Gregory Bearman & William A. Christens-Barry, PalArch’s Journal of Archaeology of Egypt/Egyptology, 6(7) (2009). Abstract:
By analogy with ancient texts, infrared imaging of ostraca has long been employed to help improve readings. We report on extensive spectral imaging of ostraca over the visible and near infrared. Spectral imaging acquires the complete spectrum for each pixel in an image; the data can be used with an extensive set of software tools that were developed originally for satellite and scientific imaging. In this case, the spectral data helps explain why infrared imaging works to improve text legibility (and why not in some cases). A better understanding of the underlying imaging mechanism points the way for inexpensive methods for taking data either in the field or at museums.