Shrink Pots

Shrink Pots with Sean Hellman

Shrink Pots

Are very democratic in that very few, simple tools are needed to make them, the materials are inexpensive and the skills readily learnt. Bowl carving needs more gouges to cut across the grain, whilst bowl turning needs a huge lathe and specialist tools.

With shrink pots – anyone can have a go!!

Inspiration

I was first inspired by this wonderful craft via a discussion thread, in the greenwood crafts section, of the Bodger’s web site which shows 2 beautiful shrink pots by Sean Hellman.

http://www.bodgers.org.uk/bb/phpBB2/viewtopic.php?f=15&t=1782

They can also be seen on Sean’s site at

http://www.seanhellman.com/woodwork/green%20woodwork/Shrink%20pots/Shrink_pots.php

Within hours I had collected some wood in the form of a small Willow branch and set to.

I used a standard auger bit to drill a hole down the center, a variety of chisels and knives to remove the bulk of the material until the walls were about 10mm thick.

Not really understanding the how, what, where and why of  “the Groove” I just drew a line with a pencil and cut it out with a knife.

A piece of dry Yew provided the base which was whittled around the edges and popped into the groove with a satisfying click.

A few days later it was dry with a tight fitting base. I was thrilled, it’s not very fancy, nor big, but it worked. However a nagging doubt in my head kept surfacing  “is it really that easy or was this beginners luck?”

 

Having A Go

My next visit to Cherry Wood saw me facilitating a shrink pot session with the two new apprentices, Kirby and Lou. It is not difficult to pass on ignorance, so I did explain that I had only made one, did not really know all the answers and that this experiential session would teach us all more about the subject.

 

We started with really wet beech which was easy to work and quickly made progress with Kirby making an additional small pot from Ash. Lou had to leave the session early and she rushed her disc making it so small that it would slip completely through the pot. My only suggestion to this was to lay it on its side while it dried.

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I was pleased with the design and shape of mine and how the disc popped in but pride comes before a fall. By the next day Kirby’s beech pot had shrunk and split which I thought was due to having it in a warm Yurt overnight. Slow drying mine in a cold garage over 5 days did not help and the pot was ripped apart by the stresses. Kirby’s Small Ash pot worked out ok. In hindsight I believe this was due to it being on the dry side to start with and therefore not shrinking much.

On the other hand Lou’s Beech pot survived the drying process – establishing the fact that the disc needs to be looser than I, at first thought.

By closely inspecting my failure I surmised that I did not know enough about groove geometry and/or depth and the disc geometry and shape, so decided it was time for some professional input.

 

Sean Hellman

Is an artist, artisan, photographer, teacher and passionate green woodworker who runs his business from Buckfastleigh on the edge of the Dartmoor National Park. He earns his living in a variety of ways including running courses including a 2 day shrink pot course in March which I attended.

You can check out all of Sean’s activities and his list off courses on his web site www.seanhellman.com.

Sean is passionate about his subject and conveys great gusto and enthusiasm to the students, he restricts this course to 4-5 to ensure that he can offer a fair share of guidance to each student.

Sean started proceedings by showing us his collection of pots from tiny to huge (60mm to 500mm high), in all shapes, sizes and woods. It was gratifying to me that not only did he show the most beautiful and skillful pots you could imagine but his failures as well. There were many pots which have split and twisted, even if he has cut a ring of a base before making a disc and test drying it. Based on experience and practice Sean expects that he would achieve 95% success rates for pots of 100mm diameter or less whilst for bigger pots this may only be 75-80%. In the beginning however you should expect your results to be worse than that until you have experienced a variety of species and how they react. Sean said “different woods and different sizes all seem to shrink differently, it is therefore best to practice on a single species and get to know it really well”

Failure may not just mean the pot breaking but also it may not shrink enough and the disc may be loose. This however can be rescued by running bees wax into the groove from the base to hold the disc in place if you want a silent disc and tighter fit.

Over a two day course you will be able to make 2-3 pots of various sizes depending on your aptitude and speed of work. On the first evening Sean takes everybody’s pots home to speed shrink them so that on the Sunday morning you can see a completed pot and make an appropriate sized lid for it.

The speed shrinking is done in the microwave oven using 30 second bursts to drive out the moisture whilst in between letting them cool, weighing, measuring and  taking moisture readings until about 15% moisture is reached and the bottom should be tight. Microwave drying is a radical approach which we are NOT recommending you try initially, as it takes much experience and lots of failures to get correct.

We are recommending slow drying in an unheated workshop shed or garage out of direct sunlight for 10-14 days turning and checking regularly to assess the progress.

My first pot kept me pretty busy all day, so much so that I did not have time to photograph the process which I agreed to do with Sean the next day.

This was of a typical tea caddy size and useful in the kitchen. It is from a piece of Ash some 115mm high by an average of 105mm wide at the base with a branch taper to the top of a few mm’s less. The Ash dried very well and had a good fitting base made of dry Larch. I had taken some of my favorite Yew with me for a lid which was too thin for a lid carved to fit inside and on top so I used a cork block to fashion a tight fitting mushroom top lid. Initially this was of a very square section which, after much discussion about the aesthetics of lid shapes I changed into a much rounder, more organic shape.
The Process

We start with cutting some wood which was from a supply of 2 week old Alder that Sean had in his outside workshop which he quickly cut to appropriate lengths for the diameter of the wood. As we are now dealing with a bigger log, 200mm at its widest point we can design either a tall pot up to 300mm high or a more squat variety which I decide will be more useful in my small shepherds hut.

The first job is to get a hole or series of holes through the log for which a scotch eyed auger of 1-2″ diameter is ideal. If you do not have one I guess most of you will have a brace and bit which will do the job just as well, if a little slower.

As always the next stage is to waste wood as quickly as you can with an In-Cannel gouge being the prefered tool. This gouge is curved down its length and has the bevel on the inside of the curve, thus facilitating a very efficient cut down the end grain we are working. I did make my first 2-3 pots with a normal gouge which works but you do need to hold it at an awkward angle for it to work. A word of caution, do not get greedy with your cuts, if you try to take a large bite out your gouge can get very stuck in the end grain and it’s a devil to remove. In the end it is much quicker to take many smaller bites and keep out of trouble.

When you get as close as you dare to the finished wall size (say 15-20mm) with gouges, it is time to even out the valleys and mountains left from the gouges using knives of some description. Sean has a great collection of homemade knives for this purpose, which are pictured, and as you will see they are all curved and have the bevel on the inside of the curve. With the pot held in a vertical shave horse I smooth and thin the walls to 10-12mm at the base to 8mm at the top to give the base enough meet to do the job but for the top to look more delicate.

Being more used to using my own tools I found that the Duncan Chandler bowl knife on the long handle was perfect for this alongside his Haida double sided blade. www.dorsetwoodlandblades.co.uk

The groove needs to be a consistent height (8-25mm depending on height of pot)from the base rim (which you have already leveled) so use what you have to do that be it a marking gauge or better still a Maples cutting gauge with the blade turned over which are about £15 from Axminster tools.

Sean has developed a croze, based on a tool coopers use, this is a fixed blade that you spin the pot around to mark and cut a line around the pot. This is a great tool and I have bought one for future use. They are available in a kit form for £18 or £30 complete, plus P&P.

Next is to go in at an angle with a knife which needs to be fairly long to get the angle and reach. This cut is similar to the shape of a number 7 on its back and is much shallower that I had previously made mine and is cut sufficiently away for it to be quite “gappy” from the disc. The idea is to cut to maybe half the wall thickness with the croze and then create the bevel to meet that point. Sean recommends a Frost 106 knife for this due to the long and slightly flexing blade, but I am sure what you are used to will be adequate.

At this stage I have only roughly finished the outside of the pot and it still looks quite a mess. Firstly this is because it has had some very rough handling up to this stage but also there is no point putting all that effort in if it breaks upon drying!

The base is a disc the same size as the internal circumference of the pot of whatever bone dry wood you have available with us using Sitka Spruce today. Sean likes to use the softer woods for this to give the pot a chance as it dries and allow a little give at edge of the disc for compression if needed. It is axed and draw knifed to a fine point at a very shallow angle thus ensuring it stays away from the shoulders of the pot as it dries, thus preventing it jamming on the shoulder. In hindsight my second pot had too steep an angle on the groove and the disc causing this jamming to happen.

The disc is a loose fit and slips in easily, if you have to push its too big, so take a little more off.

This pot is going to have a flat lid held in place by a stanchion at either end of the pot. We mark these out, one bigger than the other to aid easy orientation of the lid, and cut the pot sides down to the line. I rough out a lid from dry Ash making sure I cut the holes smaller to allow for the shrinkage of the stanchions, curve the edges nicely and give it a tooled finish with a small spoon knife and it’s time to go home.

 

The Drying Process.

This was a fascinating process to observe and one which I paid a great deal of attention to for the purposes of this article but which I may not repeat in future. I measured the weight and moisture every day, and drew the outline to see how the shape changed.

The pot started at 740 gms and 35% moisture it lost weight every day for seven days at over 30gms per day to 524gms and the moisture was down to 19%. This pot is slightly oval and has shrunk 6mm in length and 3mm in width. Most importantly, observation of the underside shows me that at the extreme ends of the length shows me that this extra shrinkage that they are both pinch points at the edge and the shoulder is touching the slope of the disc. I do some knife work of the shoulder and cut a little of the edge of the disc to make it more even all around. Maybe this action has saved the pot?

Two days later the pot weighs 490gms @ 15-17% moisture, the Spruce bottom is 15% so the pot is nearly dry and the base is firmly held all around. The physical shrinkage is now 9mm on the length and 6mm on the width.

In conclusion the most important element of the drying process was, I believe, the observation, to catch the early signs of pinching and getting the knife in there at the appropriate time. So don’t make pots and go on holiday keep your eye on them until dry.

Finishing Matters

With a dry pot it was time to finish the outside and adjust the lid to fit snuggly. I use my favorite spoke shaves and scrappers to remove the oxidization, which happens to wet Alder, and finish off with Tung oil which is food grade and has a harder, more durable finish than linseed oil and hopefully show how beautiful my pot is.

Thanks to Sean I have learnt a great deal about this great craft and I can highly recommend his course and company and I may now increase my success rate.

www.seanhellman.com