D'ERRICO, D., DRUDI, S., MAFFEZZOLI, D. and VENDITTI, F. - Production of pitch #1

The first step of the experiment consisted in the construction of a stone cist, positioned at the center of a 40 cm-deep pit (Phase 1). At that point, we tied together 16 cylinders of birch bark and positioned them in the cist in such a way that the pitch would later flow downwards and be ready to collection (Phase 2). The cist was closed with a stone slab on the top. In building up the sides, we left earth-filled spaces to be used to stir the ashes - in order to increase and equally distribute the heat (Phase 3).

 

The next step consisted in lighting a fire above the closing slab, so that the heat could begin penetrating within the cist. We fed the fire for about an hour before totally covering the cist with ashes (Phase 4). After another hour we gradually buried the pit with earth in order to maintain the heat (Phase 5).

 

Two hours later we carefully unearthed the cist and removed the closing slab which had cracked with the heat (Phase 6). While we were removing the birch bark cylinders, an accidental dispersion of ashes caused a burst of flames during the uncovering of the cist. Once the fire was extinguished, we proceeded to remove the pitch we were able to obtain from the bottom of the cist.

The experiment resulted in a small quantity of pitch, far less than expected. In our opinion, this was due to both an insufficient number of birch bark cylinders and to the premature opening of the lithic cist during the firing process, which caused the burning of the remain cylinders.