Object
The object is a wooden barrel top consisting of five main staves, which was uncovered during excavations of Holyrood Road in Edinburgh in preparation for new student accomodation being built.
The site occupied what were once the medieval backlands of the south-west corner of the historic burgh of Canongate; the burgh got its name from the Canons of Holyrood Abbey, which was established in 1128. The backlands typically formed areas to the rear of the houses which would have been used for industrial purposes and later on for gardens. In the 19th century and up in to the 20th century the area was occupied by the Edinburgh & Leith Brewery before being redeveloped in the 1970’s for Edinburgh University (https://www.cfa-archaeology.co.uk/2014/09/holyrood-north-archaeological-excavations/).
Dendrochronological analysis of another barrel top at the site dated it to around the 14th century and research indicated a provenance of the Burgundy region, making it certain it would have originally been a wine barrel. However dendrochronological analysis of the barrel to be treated was not as straightforward as although it was a similar size and shape, it did not date against any French chronologies.
The lack of correlation between the staves and the presence of three bung holes suggests a long life and a period of repair and replacement, which may be why the analysis was not successful. But this in itself is quite interesting as it shows how objects were reused and recycled in the past rather than just thrown out.
Condition
- Arrived into the lab in waterlogged condition
- Evidence of dirt on the surface of the staves
- There is a crack along the thickest of the staves.
Conservation
In order to remove the surface dirt from the staves they were placed onto a net frame over a sink and with a thin stream of water. A soft bristled brush was used to brush the dirt from the surface, and the water assisted as it softened the dirt and made it easier to remove. Anything that couldn’t be removed using a soft brush was left and would be looked at once stabilisation treatment was completed.
Before the moisture could be removed the wood required stabilising. If waterlogged wood is allowed to dry out before being stabilised it could end up shrinking and cracking as the degraded, fragile cells can collapse as the moisture is removed.
The waterlogged staves were placed into a tank with 10% PEG 400 in water. They remained in this tank for two weeks, stirring every few days. After two weeks 10% PEG4000 was added and the solution was stirred in order mix the PEG4000 into the existing solution. This process was repeated every two weeks until the overall solution reached 40%.
Once the staves had been in the 40% PEG solution for two weeks the staves were removed, rinsed briefly to remove PEG from the surface and then placed into the freezer, at -20C for one week to ensure all moisture was frozen. The staves were then placed into the freeze dryer until all moisture was removed and the staves reached room temperature.
Following moisture removal, the excess PEG on the surface was heated with a hot air blower in order to allow it to be absorbed into the surface.
The widest of the staves had a prominent split running across the width, which had slightly worsened during the treatment process. In order to stabilise this split, coloured wax was melted and used to fill the split. This helped to stabilise the split and using coloured wax allowed the fill to blend with the rest of the wood. Using wax also meant the fill could be removed at a later date using heat if necessary.