Wednesday, 18 February 2015
In the bleak midwinter - lime and coda
From Castle Stalker we used the sails to speed our passage across to Shuna Island. There's another island called Shuna, somewhat further south at the mouth of Loch Melfort, but the one we were headed for is the Loch Linnhe version. We paddled up the west side until we found a fine place for luncheon on a small sandy beach at the head of a bay and sheltered from the wind.
After a leisurely lunch stop we headed around the north tip of Shuna and straight into a stiff southeasterly breeze. It requred a reasonable amount of effort to push against both the wind and the start of the flood tide, but ahead of us was a great view down the Lynn of Lorn to the Garvellachs, the scene lit by occasional shafts of watery winter sunlight.
After circumnavigating Shuna we continued south and made our way to Eilean nan Caorach (Sheep Island) where we landed in front of the cottages and industrial relics. The base rock heareabouts is lime-rich and was quarried quite extensively. the cottages would have been occupied by the quarrymen and lime-burners, there is a storehouse, a pier and three single-chamber lime kilns, all of differing designs.
The smallest of the three kilns appears to be the oldest and is in a fairly ruinous state. given the extensive cracks down the walls we were disinclined to venture within!
The largest of the three may well be the most recent and is in a sound condition. The rock was quarried and in this style of kiln would have been broken to lumps and layered with coal or coke on a raised grate. The size of the lumps was important because the fire had to "breathe". The fire would be lit and at approximately 900 degrees Celcius a chemical reaction (calcination) initiated and quicklime produced which could be raked through the grate.
Most lime kilns are of a very similar size as a result of optimisation. The aperture was known as the "eye" and the chamber is almost always eggcup shaped. Usually a batch took a day to load, three days to fire, two days to cool and a day to unload. Typically 25-30 tonnes of lime would be produced in a batch, requiring about 12-15 tonnes of coal to fuel the fire. The quicklime which was produced was quite caustic but could be altered to make lime for mortar and for agricultural use. It must have been hot, dangerous work and it's difficult to believe that life expectancy was very high for the workers. The kilns on Eilean nan Caorach and nearby Lismore were active from the 1790's until well through the 1800's.
From above, the size of the flue is obvious.......
...and from inside the burning chamber the inticate brickwork is seen to good effect; a fine Victorian engineering job.
We moved on from Eilean nan Caorach a little further south, to Port Ramsay at the north tip of Lismore (Lios Mor - big garden) No doubt the gaelic name is indicative of the fertility of this limestone-rich island.
We made a brief coffee stop on one of the small tidal islands clustered just off Port ramsay and enjoyed the view back over Eilean nan Caorach and Shuna to the Appin shore. Our midwinter trip was almost over, but we had one last treat in store....
Heading out past the north tip of Lismore we were exposed to the full force of the flood tide as it compressed through the north end of the Lynn of Lorn. We had to PLF for a good ten minutes to get around the small skerries and then set up for a ferry-glide back to Port Appin; it certainly rewarmed us!
To the south, a vivid streak of sunset colour beyond the Garvellachs developed across the horizon, providing the perfect coda to a great winter trip.
It hadn't turned out to be a bleak midwinter at all!