Thursday, 9 December 2010

Dating in the Vale of Ffestiniog

There are several ancient houses in the upper reaches of the Vale of Ffestiniog but just how old are they?

A few years ago Plas Pengwern, betweeen Blaenau and Llan, was tree ring dated and the result was autumn 1487. That is the date when the tree was felled and subsequently used to create the main beams of the house.

Seeing as the practice was to work with green oak, that is the date when building began.

Now there is a major project under way called Dating Old Welsh Houses with funding from, amongst others, the Heritage Lottery Fund. The aim is to research and date about 50 houses across north Wales and 5 are in the Vale of Ffestiniog.

S4C recently broadcast a series titled Houses of the Welsh Countryside and in the episode titled Tai Eryri (houses of Snowdonia) they included Bryn Rodyn in Cwm Cynfal. The programme showed the dendrochronology experts at work and the date was concluded to be between 1556 and 1560 although they also discovered some older beams from 1503 which had been recycled into the building.

Recently it was the turn of Plas y Dduallt, beside the Ffestiniog Railway, to be dated. Dan and Matt, experts from the Oxford Dendrochronology Laboratory, arrived and began to study the wood. Looking at the grain and texture with the help of a torch they seemed happy. ‘Hmmm. Nice rings. Bit of sapwood here.’ Thank goodness for that. Within minutes strips of blue sticky tape were being stuck around the house to mark the sample spots and the various drills and spotlights were brought in from the cars.

Sapwood, the youngest final layers of growth, could have been an issue because of the work done by Colonel Campbell. As part of his 1960s restoration work he’d chamfered just about every beam to make them look more ornate, typically removing most of the sapwood. But fortunately there was still sufficient in tact.

A shower of well seasoned sawdust was falling onto the slate slab floor as the first of six cores was extracted from the dining hall. The thickness of a finger and length from 6 to maybe 15 inches depending on the size of the timber and angle of attack. An ideal sample would begin with sapwood and finish at the centre of the trunk.

The first core was teased out of the drill’s hollow tube and examined. Not only sapwood but masses of rings, the minimum required being 80 to 100. At the sapwood end the rings look straight but by the time you get to the centre you can clearly see the arcs of the rings.

By comparing the ages of the ceiling beams with those in the bedroom above we will be able to rule in or out the theory that the building began life as a hall house, open from the floor to the roof, with a subsequent first floor conversion.

Dan started upstairs on the cruck beams, entering from the side that people would be unlikely to see, with me standing guard the other side. My job to shout on seeing the first puffs of sawdust so that drilling could stop before breaking through. This would avoid the need for sealing the hole with a plug dyed to match the surrounding wood.

Drilling is done with surgical care and precision. One of the challenges is to extract cores from timbers which have cracked or split as the wood has seasoned in place. Having identified faint cracks from the outside the drilling is done to anticipate the point at which the drill will meet the split and the core will snap. This needs removing, before continuing with the rest of the core, and then sticking onto the other piece with a bit of wood glue. Removing the sapwood is another challenge as this is crumbly, the outer zone where beetles and woodworm will have penetrated.

In between the noisy drilling and over cups of tea there was time to chat about the science and projects past. One of Dan’s more unusual projects had been to date some trees planted, according to the plaque, by George Washington. The caretaker was devastated with the result that the trees were post 1799 and could not possibly have been planted by the famous man. The following year he hired another dendrochronology expert and as you’d expect the result was that the tree was a year older than Dan’s calculation.

I mentioned the yew trees in Maentwrog churchyard having an official certificate, issued by the botanist David Bellamy, confirming them to be more than 1,300 years old. Dan didn’t seem too impressed. This is one of those assertions that is a bit difficult to prove by dendrochronology as the cores of ancient yews have generally rotted away. Calculations and estimates are typically made by applying a girth formula.

At the end of the day about 15 cores had been extracted from four rooms. These were carefully plotted on to a plan of the house and recorded onto a record sheet with schematic diagrams of each beam. Back at the lab the cores will be sanded down to reveal clear and easy to read rings for measurement and comparison with growth patterns for the UK. All being well we will know the dates in early 2011.

As the team packed their tools away our 5 month old puppy, who had been watching on with keen interest, ran under the table with a piece of wood in her mouth. Removing it from her teeth I returned the chewed core to Dan and was relieved to learn this piece was not required for analysis. Fetch!

If you’d like to see a short film of how the drilling is done, click here.

If you’d like to know more about the Dating Old Welsh Houses project, click here.

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