Red Ochre And Its Uses

Julie had a good day last Friday in Trench 34/41 , exposing more of the red ochre and charcoal deposits. On reflection this is not looking hearth like due to the  naturally coloured clay and soil the ochre and charcoal are mixed with. However, we may just not have found the seat of the hearth, the magnetometry response shows a larger area not yet explored. So it was decided to take a sondage down the east side to ascertain the depth on the ochre deposit and the trench will be enlarged when conditions allow. 

Last Wednesday I met an engineer who is helping on the restoration of the Webb's Heath Drift Mine. It turns out he had experience in foundry works and the subject of ochre cropped up.   He informed me red ochre was and still is used in the foundry casting process, it is mixed with the usual green sand for colouration and can also enhance certain moulded objects finish.

 In recent XRF analysing a small iron content was present in many of the copper alloy object, the use of red ochre in moulds could be one of many explanations why. As with the melting point of iron being so much higher its presence is not obvious, equally it could  just be unintended residue.  

With every trench dug in the Glebe it becomes clearer foundry works probably took place here, so we now have another possible use for the red ochre we are finding.  The three possible uses being, 1. for ink manufacture 2. making into a paste for marking or even decorating livestock and 3. used in foundry mould making (but it is unclear at the moment if this happened in the medieval process). 

David