A Reproduction, Not a Test of the Relic Itself

In 1991 the chemist Luigi Garlaschelli, with Franco Ramaccini and Sergio Della Sala, published a study in the journal Nature proposing that the relic's contents could behave as a thixotropic gel, a substance that is solid or semi-solid at rest and turns liquid when agitated or disturbed, then returns to its resting state. Using chalk, iron chloride and other materials that would have been available in fourteenth century Naples, they produced a mixture with the correct dark brown color that stayed solid when left still and turned fluid when shaken or stirred, closely resembling the described behavior of the relic.

Because the Church has never permitted direct chemical sampling of the sealed vials, Garlaschelli's result is a demonstration that a mundane substance can be made to reproduce the reported effect using only medieval materials and techniques, not a laboratory finding about what the vials actually contain. Both proponents and skeptics agree on that distinction; they disagree on how much weight a successful reproduction should carry when the original material itself remains untested. Garlaschelli has since applied similar thixotropic reasoning to other reported blood relics in southern Italy, arguing the recipe was plausibly available to medieval custodians even if it was never written down as a formula.