Inspired by the great Youtube video Harry Rogers posted of the Kent Bodgers making shrink pots a couple of years ago the Oxfordshire Bodgers decided to theme one of its winter meetings around making shrink pots.
The process involves carving out the centre of a freshly felled green wood log to create a hollow tube and then to gouge a groove at the bottom edge to fit a custom-carved base of dry wood. As the pot seasons and dries, the greatest shrinkage is in the tangential plane, in other words the circumference of the pot reduces, which then tightens onto the dry base, locking it into the groove and possibly creating a water-tight fit if the base aligns well with the groove.
We were the hosts of Willowbrook Farm near Kidlington just North of Oxford and although we had booked the use of their indoor classroom the December weather gods smiled on us and it was mild enough to work outside, although with frequent trips indoors to the the tea urn and the biscuits.
We were joined by new member David who as a groundsman at Oxford University has access to recently felled timber and brought some lovely birch. Indeed, so fresh was the wood that as it was being drilled at one end the pressure was driving out the sap at the other end to create a moisture shadow of the spinning bit in the end grain of the wood.
None of the group were expert shrink-potters so it was a true skill share and experiment day. One of the biggest challenges with making shrink pots outside of a workshop is clamping them down, especially for drilling or augering the initial hole through the end grain of the log.
We had a variety of techniques on the go, including the use of portable workbenches, and a bowl-horse.
Perhaps the simplest approach, to use a pair of wooden clamps to hold the log at ground level by standing on the clamps and then drilling with an auger, thus allowing the full weight of the body to help drive the auger through the end grain.
Augering two or three holes on the end grain worked best to then help with the removal of waste from the centre of the pot. We had a variety of drill bit and auger sizes to play with. One inch to one and a quarter inch (25 to 30 mm) bits seemed to work the best. I had brought along a two inch auger which shifted a lot of wood but was very hard going through end grain.
Once the initial hole had been drilled through the log then the work needed to be brought to a decent working height on a bench to allow for gouging out the remainder of the wood. Again the pot needed to be clamped in position. We had a variety of gouges available. Carving gouges with the bevel on the outside could be used at a pinch, but required the gouge to be angled in to the wall of the pot to rest on the short reference surface of the outer bevel. I found it easiest to use a one inch (25 mm) in-cannel gouge (sometimes referred to as a paring gouge) as this allowed the gouge to be used straight down and created a relatively smooth inner surface.
Judging the thickness of the wall of the shrink pot was important, taking into account the need to sink a groove into the base of the pot. The silver birch bark looked lovely and most folk had opted to retain the bark to create a rustic look to their pots. Even if the final pot is likely to have the bark removed, in decision to take off the outer bark before angering or leave it on is an interesting one. Leaving the bark protects the piece from clamping marks, but again it depends on whether the point is going to follow the shape of the log or to be defined by the maker and hence remove more of the outer edge of the pot.
Hook knives were used to smooth the final inner surface of the pot after gouging. I had a relatively shallow hand forged hook knife on a long handle that worked well for this task.
Next was cutting out the groove. Eddie was able to help out here with another of his amazing Bodger’s Ball tool purchases, a complete set of Flexcut right-handed scores and v tools of various sizes. A marking gauge could be used to score the wood at the appropriate depth and the scores, with their blades at right angles to the handle were perfect for cutting a groove of around 1/8 to 3/16 inch (3 to 5 mm) depth in the wood.
Both Eddie and Phil had kindly brought some dried wood to use as the base and so next up was carving the base to size and thinning the edge to fit the groove. The tighter the initial fit, the greater the chance of a tight seal, but care has to be taken that if the groove isn’t deep enough, the pot could split as it shrinks too much around the base.
That was about as far as we could get for our session, Aimee won the prize for productivity, preparing three birch pots during the day! Letting them dry slowly to reduce the chance of splitting is important. I personally favour a thick paper bag to control moisture loss and find that flour bags fit the bill.
Once the pot is dry and the base locked in place then it is possible to design and fit a lid.
Willowbrook Farm was a great venue for our activities and visits from the farm animals on site certainly enlivened our day. Using the well designed and smell-free compost toilets was also a pleasure! I hope our group can come and visit again soon.