When the editors of the Talmudic Encyclopedia approached Dr. Israel Ziderman in 1969 to summarize the doctoral thesis on tekhelet written in 1913 by Rabbi Isaac Halevi Herzog, former chief Rabbi of Israel, it was the first time that Dr. Ziderman studied the tekhelet. As a scientist and religious person, Dr. Ziderman was well versed in both required fields – life sciences and Torah. “I performed the mitzvah of Kriyat Shema twice a day, and recited the verses of the third paragraph, but until then I did not think so much about “and that they put on the tassel of each corner a cord of tekhelet,” says Dr. Ziderman.
This was his first step in the field of tekhelet, following the findings of Rabbi Herzog, and over the years he has become a worldwide authority on the tekhelet. Dr. Ziderman authored the scientific proof for the identification of the banded dye-murex as the snail used to produce the ancient tekhelet. He also studied Talmudic sources on the tekhelet in order to substantiate his scientific results.
Back in the 1970s Dr. Ziderman approached Haifa University, where he was provided with live specimens of the species of sea-snails that produce the Biblical tekhelet and purple dyes. Dr. Ziderman conducted experiments on these snails and was successful in producing the required colours from them, thus corroborating the theory that banded dye-murex is, in fact, the original snail used in antiquity for dyeing the tekhelet for the tzitzit and High Priests’ clothing.
In order to promote and fund his study, Dr. Ziderman founded the Tekhelet Foundation in 1984. The publication of his studies and his public promotional activities lead to the establishment of the Ptil Tekhelet Association that began to market tekhelet for the tzitzit tassels. Dr. Ziderman has recently been engaged in studying the chemistry of the tekhelet dyestuff ingredients that affect its shade of colour, together with scientists in laboratories in Israel and abroad.