Shrink Pots

First Shrink Pot. It seems that Greenwood workers like to make these, and having read about them, I thought I would give them a try. Basically the principle is straight forward but I expect that the skill is something that develops with experience. The job starts with a branch of green wood. The diameter isn't crucial but needs to be big enough to be able to work inside the pot. I used a stem of hazel wood about 3 inches in diameter and 7 inches long. The idea is to remove the inside of the log to make it hollow, the shape can reflect the original form of the branch or stem or you can modify it by carving the outside later and even doing some pyrography on the outside for decoration. At this stage the bark can be removed or left on, and then a narrow channel made around the inside circumference to which the bottom can be inserted. The bottom must be dried timber so that when the pot dries and shrinks, the bottom is held firmly in place.

My first task was to select the hazel and remove as much internal wood as I could be drilling, but leaving about 3/8 th inch thickness wall.

Using a 1 1/4 inch bull-nosed auger to hollow-out the pot.

As I was drilling into the end grain of the log, I found that a bull-nosed auger did a good job of removing wood quickly and proved effective. I'm sure there are lots of ways to drill out the centre e.g. just making one hole and using a carving knife to remove wood to get a good diameter.

After drilling four holes, I removed the rest of the wood using a gauge and crook knife.

Gauging out the wood between the holes.

I should have taken more care at this stage as it proven easy to tear-out too much of the wall, making it too thin and a weak spot when the pot shrinks.

This is the bottom of the pot after making the rim channel to eventually hold the bottom piece of wood. As you can see the wall of the bottom is particularly thin in one place.

The bottom was sawn and planed to 5 mm thickness, from of a piece of air-dried hazel. The shape was carefully scribed on the bottom through the inside of the pot also marking the orientation. The size and edges were cut or filed to a "v" shape so that the plate fitted neatly into the pot. This clicked into place easily but wasn't loose. This I think is where experience will be invaluable in judging the tightness of the fit according to the size and wall thickness of the pot. Too loose and shrinkage will not hold the plate and if it  is too tight, the base may force the pot sides to split.

Base plate now inserted.

It doesn't appear critical, but the shape of the inside channel was determined by the marking gauge scribe, i.e. the upper wall of the channel was vertical to the side of the wall, and the lower part of the channel was "v" shaped, i.e. sloped from the wall. I think the plate needs to be pointed around the outer rim to ease fitting and also to make it easier for the walls to contract on drying and press against the   plate.

The pot after treating with oil. 

The mistake with the wall thickness did lead to a small 1 mm crack near the bottom of the pot that I filled with brown epoxy resin so that the pot wasn't wasted. 

After drying for a few days, I made a lid from some air-dried hazel including a knob (made on the pole lathe from some hazel). Fitting the lid was tricky because of the uneven shape. First, the lid was planed to 1/2 inch thickness and the shaped with a coping saw and small spokeshave. The kerfing plane (with a fine toothed blade) was used to mark and saw one side of a rebate in the lid. The remainder was then chiselled out and small adjustments were made using a fine wood file. This took some time with minor adjustments until the fit was good.

The outside of the pot was then decorated by gauging-out dimples and marking their perimeter by pyrography.

The pot with an hazel lid after the sides were gauged and further decorated by pyrography.

This shows the other side of the pot after pyrography. The split has been filled with coloured epoxy and enlarged as tree branches!!

Anyway, this is my first shrink pot and I have learned a lot about the techniques so that I look forward to trying another.

Second Shrink Pot.

Soon after making that, I tried some more shrink pots using the same stem of hazel and basically the same method but taking more care of the excavations. I have a shallow crook knife that I hadn't found to be very useful for spoon or kuksa carving, but came into its own when carving-out the inside faces of the pots. I also sharpened the edge on the marking gauge and used a small gauge to make the channel in the base. This time a used a piece of dried ash for the base.

Here you can see the channel carved in the inside of the second pot

Second pot left to dry for a couple of weeks before making the top.

Third Shrink Pot.  I decided to use a diameter to height ratio of 1.6 (the so called magic ratio) so made the third pot slightly higher, 6 inches. The wood and methodology were the same as I used making the other pots but I needed to level the base and top to get even surfaces after sawing. This time I used a piece of beech for the base and the fitting went well, just a case of iterative adjustments to get a tight fit.  I continued to make a "v" shape around the edge of the circumference of the bottom plate, mostly using a small spokeshave and fine wood file. Six inches is probably the deepest I'd want to go at this diameter with the carving tools that I have. There was a little movement after fitting the base that soon went after a day drying.

The third pot after fitting the base. Notice some detail on the outside because of knots.

The two larger pots were left to dry for a couple of weeks (temperatures outside around 17 C) before making the lids from kiln dried beech.

Pots left to dry.

Shrink Pot Lids.

I made three lids. One was from some hazel that turned out to be still drying and two from some kiln dried beech. The hazel lid was fine as I was able to adjust the fit after it dried. I will describe the method I used to make the other two lids.

I started with a square of beech (2.5 cm thickness) and marked the outside circumference around the top of the pot and then drew a line about 5 mm outside of this to allow the lid to overlap the top of the pot.  I then used a turning saw to get the right basic shape as shown:

Cutting the lid shape.

The lid was then planed to shape using a small spokeshave.

The underside of the lid after planing and marking for the rebate. The crosses show the wood to be removed to the depth of the rebate.

The width of the pot's rim was measured with a vernier and another mark made on the bottom of the lid to show the position of the inside edge of the pot. This is the depth of the rebate for the lid to fit the pot. This means it is important to try and get the upper edge of the rim the same thickness around the circumference of the pot.

The rebate was then marked to the approximate depth around the circumference of the lid using the kerfing plane with a fine toothed blade:

The kerfing plane being used to mark the position of the rebate. The depth of the cut was marked on the plane blade,

The rebate was then chiselled being careful to watch the direction of the grain and avoid any splitting.

The rebate being chiselled to the inner mark to allow the lid to fit inside the pot.

The rebate was cleaned and checked for the fit to the pot. It is important to have a pencil mark to check the orientation of the lid. It took some time to fine-tune the side of the rebate to fit the pot. I did this by fitting one end into place and then marking the points were there was some interference and then chiselling around the side as needed. In fact, the pencil line as marked on the inside gave a close fit.

The lid was then placed on the pot and the overlap from the pot sides was adjusted to 4 mm and then planed to size with a small spokeshave. The top of the lid was then shaped so that the centre area for fitting a knob was flat, but the rest curved to give the outer thickness of  5 mm. A knob for the top was made from hazel on the pole lathe and left to dry before fitting.

The underside of the lid carved to fit the inside of the pot with a small overhang on top of the pot.

The domed top of the lid that is the same shape as the top of the pot with a 4 mm overhang. The photos also shows two knobs made for the lid. 

I made a second lid in the same way but left less overhang on the side. I also embellished the knots on the second pot by pyrography.

The finished pots after treatment with Danish oil.

The pots took longer to dry than I'd expected as indicated by the fit of the lids. I left them another month (in the summer) and then adjusted them as needed and this seems to have done the trick. This means they took about two months to dry in warm and dry conditions.

 Note:  These are some notes from Tomas provided to Dave Fisher (on Pinterest) about their construction that might be helpful in future work (quoting) and in getting a water tight seal at the bottom of the pot (or box).

"These kind of shrink boxes were quite common in the shepherd culture of Eastern Europe where I live. A while ago I studied their construction a bit and found the following:

1. The box is made from harder wood while the bottom from a very dry softwood, usually pine.

2. The edges on the bottom are shaped not in a V shape but rather in I/ shape such that the flat part (I) id heading inside the box.

3. The groove in the box is thin, not so shallow and , if possible, in a I/ shape with a smaller angle of the edge of the bottom.

4. Before putting the bottom, they dried it in a stove (or near a fire) while keeping the bottom of the box in hot water. Thus, when they put the bottom to the box, the dry bottom started to expand, the boiled box started to shrink and since the groove is with a smaller angle and the edge of the bottom is with a larger these two were tightened well.

5. In some places they used to fill the groove with a tiny band of dry reed mace (they used to use it also for isolating barrels. "

I believe that Reed Mace is the same as Bulrush. 

As I am using greenwood for the pot, I'm not sure that putting the pot in hot water is necessary and that the natural shrinkage on drying should be enough. However, the tips on the groove shape are interesting and I will try this in future.

Shape of grooves to get a water-tight seal, perhaps!

Forth shrink pot.

My next pot was from some windfall spalted sycamore. This was 11 cm in height and 9 cm outside diameter. This was excavated using a 1 1/8 inch bull-nosed auger and finished in the way described above with a base of poplar made as described in the diagram above.

The ash pot ready to dry.

The polar base fitted leaving some space for the pot to shrink whilst drying.

The first coat of milk-paint. 

I had decided to decorate this pot by relief carving some details on the surface, hanging leaves, and use milk-paint to enhance the design. I used a 1:2 powder to water mix for the top and bottom rims and a more diluted mix (1:4) for the leaves. I initially tried a very dilute mix on the entire outside but this showed more on the spalted wood and less on the other. This is my first attempt at using milk-paint.

After three coats of milk-paint and some "spotting" to mimic the effects of the spalted area of the pot.

The finished pot after a final treatment with danish oil.

The application of danish oil after leaving the three coats of milk-paint to dry for a day, produced a brighter sheen.

Fifth shrink pot.

This was also made from some spalted sycamore but had a larger diameter base and was more difficult to carve-out because of the grain.

Drilling three holes through the branch with a 1 1/4 inch bit.

Multicolours revealed as the bark and cambian are peeled away. The underlying wood was spalted.

The outerlayers were removed with a drawknife and spokeshave and a poplar bottom cut for insertion. This was more difficult because of the irregular cross section of the branch.

Pot 5 left to dry with the bottom inserted. Note the bluish spalted colour of the wood.

Final version after painting and relief carving.

Sixth shrink pot or tube.

Another option is to make shrink tubes. Shrink pots need to be of sufficient diameter to excavate easily starting with a drilled-out hole or holes and working from there with a gauge or crook- knife. However, the other obvious option is to use a large drill to make the inside without any additional carving. 

I tried this with a freshly cut piece of hazel of about two inches diameter, as an experiment. I drilled this with a 1 1/8 th inch bull-nosed auger by drilling from each end and meeting in the middle. As this was still very green, it was left to dry for a week (at 10 to 15 C in the workshop). Another option is to shape the outside of the green wood on the pole lathe before cutting the central hole.

Tube of hazel 14 cm in length and drilled to 1 1/8 th inch inside and left to dry.

View of the ash bottom before shrinking.

View of the hazel top before drying and completing the carving.

Finished tube used as a desk pencil holder

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The tube was treated with danish oil (1 coat) and then some balloons carved out to show the underlying whiter wood. Finally, the balloon perimeters were outlined with a pyrography pen. This kept the natural wood effect.

I did try drilling a hole to make a tube but leaving a base in place (i.e. not drilling right through the tube) but both times I tried this, the auger split the the bottom and the sides when the drill reached about 2 cm from the bottom. I did have some success by leaving the sides of the tube thick, about 1 cm, with a smaller central hole. 

Seventh shrink pot made from a branch of ash.

The pot after shaping and fitting a bottom.

This one was made from fresh green wood about 7 cm outside diameter and 14 cm in length. This time I drilled a 1 1/4 inch diameter hole in the centre, drilling from both ends to the centre. The pot was excavated using a bent gauge and skew-knife leaving the side about 8 mm thick. A bottom of dried poplar was fitted as described before and a top also shaped to fit inside the pot, leaving a little room for contraction of the pot as it dries. This will be glued to a wider top covering the rim as described below.

View of the bottom of the pot before drying.

I made the top of two pieces of poplar, one that fitted inside the top and another glued on top to fit the outside diameter of the pot. This method is perhaps easier than making the top from one piece of wood because the inside marking and fitting is simplified. 

The top carved to shape.

The side of the pot was carved by making vertical grooves that lined with the top channels to produce a serrated surface.  A knob was also carved from a piece of dried hazel and shaped to complement the top. A hole of 1/2 inch diameter was drilled to accommodate the knob and the stem fixed from the inside with an hardwood wedge. The pot was left to dry for a few days before treating with danish oil. 

Finished ash pot after treatment of the outside with danish oil.

Eighth Pot...Not shrink but a vase!

This was just a idea of making a vase without removing the base but keeping the internal diameter quite small. This will be good as a dried flower vase or with a glass jar inserted, as a flower jar.

I started with a green ash log that happened to be oval in cross-section so not ideal for the pole lathe but this was just a trial to see how the piece shaped-up. The end-grains were planed parallel and the centres estimated. The log was trimmed a little by axe and draw-knife to get cylindrical shapes at both ends but leaving as much bark on in the middle section. This was then mounted on the spindle lathe and each end shaped with the centre section and bark left intact ready for further hand-carving. I then converted the lathe to its bowl carving configuration and used the tip-up and tip-down gouge tools to make a bowl like base or stand with a concave centre. This would allow some movement in the wood when drying but keep a stable base for standing. Some finer details were also gouged in the log at this stage, see photo below. 

After the pole lathe work was completed, the log was removed and mounted in wooden screw-vice to drill the central hole. This was done easily with  1 1/4 inch bull-nosed auger and brace being careful to keep the hole central and finishing about 1 inch above the bottom. The top of the central hole was fluted with some carving gouges.

Vase showing some ash bark left after turning and the central holder drilled.

The other side of the vase were the bark was removed and some pyrography details added, i.e. ash leaves and seeds. The channels on this side were hand carved.

Finished ash vase after sanding and treating with a coat of danish oil.
The vase was 15 cm tall and 8 cm wide at it's widest point and the opening was 4 cm diameter.

The bulkier wall thickness and weight of the vase should make it stable and ideal for displaying dried flowers.