Shrink pot. A picture tutorial.

While roaming the internet I found that there seems to be more information out there on how to make shrink rays than there is on shrink pots. There are some write ups done about them by people that are far more knowledgeable than me. Examples: Here is a blog post by Mark Emery, here is one by Robin Wood, and of course Sean Hellman makes fanstastic shrink pots as can be seen here. What I found lacking on the net, however, was a clear tutorial for novices such as myself. People nearly as green as the wood they work. And therefore I decided to produce such a tutorial in the hope that other green woodworkers have a place to start from. 

A shrink pot is a container that is made from a hollowed log of green wood. The bottom is made to fit the inside of the hollowed log and inserted into a groove that is cut near the bottom end. The green wood will shrink and lock around the bottom, resulting in a nice watertight container. They are fun to make and do not require much tools. I use a drill, a spoon knife and a knife for them. For materials you`ll need a bit of green round wood to make the actual pot, and another bit to make a board with for the bottom. This board is ideally made out of dried wood, but using green wood can also be done. Wood shrinks a lot more radially than length- or widthwise, and therefore the pot will lock the bottom in place fine. For the pot in this tutorial I used an apple branch for the pot itself and a some dry oak for the bottom.

First cut the wood to length and drill a hole through the middle. I use a powerdrill and a 25mm flatbit, but it could of course also be done with an auger or handpowered drill. When you use an auger it might be easier to drill the hole first and then cut the wood to length afterwards. The hole will give the spoonknife an edge to bite on and will speed the whole thing up a lot. 

 Here are the tools I used. A mora 164 and my carving knife (a rehandled mora 511). I am quite certain that the spoon knife is just a luxury to have here and that the whole pot can be made with the straight knife. The spoon knife is just more convenient and a bit quicker when it comes to hollowing out the pot.

 

Work the pot from both ends taking care to achieve an even wall thickness. I do not think there is a rule for wall thickness. Thicker walls will press on the bottom plate tighter when they shrink, but that also brings the risk of the bottom shifting or cracking in the drying process higher. This can again be alleviated by cutting a deeper groove and using a thicker bottom plate. You can play around with it a lot. I haven`t made enough of these to give sound advice from experience yet. I have, however, seen a lot of these on the net, and for this size (10 cm high, 7cm wide, bark not counted) a 1cm wall seems fair. I did not count the bark with the wall thickness or diameter. The bark does not add to the structure of the pot and is only there to look rustic. 

When the walls are thin enough for your liking, it is time to cut the groove. Determine what side of the pot will be the bottom, and draw a line spaced about 1 cm up from the bottom on the inner wall. 

 Then, using your straight knife, make a cut about 1.5mm to 2mm deep over the line. It is important to make this cut in a 90 degree angle relative to the longitudinal axis of the pot. That is because this cut will form the ridge against which the bottom plate will later rest.

 Then follows a part that I could not photograph on my own while making the cut, so I`ll describe it as well as I can. Coming in from the bottom side, make a cut that is similar to the previous one, but angled 45 degrees downward. This will remove a bit of wood resulting in a groove that has a sharp edge at the top and a more tapered edge towards the bottom. This will help the bottom plate slide in and lock on place. Here is a bad picture of the groove.

It is then time to carve the bottom plate. Begin with flattening the material you want to make the bottom from, and get it near to the appropriate thickness. In this case that is a few mm. Place the pot on the material and trace the inner diameter onto the wood with a pencil. I also like to mark the orientation of the bottom plate with a line on both the pot and the plate. I noticed it is not always obvious how the orientation of the plate was after you spent some time whittling it down, and such a mark that tells you exactly how you planned to put it in really helps. From here on it is just a game of trimming the plate down untill it just fits into the tube of wood. I find that tapering the edges of the bottom plate helps to achieve a good fit.

 When you can just about push the plate into the tube, tap it in further with your knife handle. If all is well it will click into the groove.

That is essentially it. You have now succesfully made a shrink pot. All that rests is waiting for it to actually shrink and gain a tight fit on the bottom. I trimmed the top edges of the pot a bit, and called it done. Here it is in a picture with my Opinel #8 for scale.

And a picture of what the bottom ended up looking like in better light. 

The pot can now be used. What for? Well, typically they are equipped with a fitting lid and used as containers for dry goods like spices etc. I like the idea of using one to grow herbs in in the kitchen. Momentarily it stands on a shelf holding some wooden spoons. Once dried it will get promoted to function as a cinnamon-container, I think.

I hope this tutorial is clear and inspires some people to have a go. Making a  shrink pot is very achievable, and doesn`t take so long. In fact, it took me longer to complete this blog post than it did to make the pot.