Or perhaps "Harlech Raku?" would be more appropriate. This is the story of my attempt to make pots using clay from the local estuary ,and it's an ongoing scenario - quite a few failures along with the occasional success of a firing of pots that ring nicely - & that's enough to keep me trying to find the right way of preparing the clay , firing temp , glaze and so forth.
Why Raku? Because it seems a reasonable low-fired way to proceed . And the thing that got me interested in pots in the first place was doing a daytime class at Harlech college with tutor Geoff Bond , who organised a day of Raku firing in a brick kiln built for the day and fired with wood . It was a great day , some fantastic pots and a good time was had by all , inspiring in my case even if it took a few years to germinate the seed. ( Bless all vocational class tutors and the effort they make to fire the imaginations of their raggle-taggle bunch of students!)
So ... it's a simple process , as it has been down the centuries , you dig up the clay , mould it into a shape , and stick in in a fire until it goes hard .
The first bit is fairly easy , find your clay and dig it up. In this case the seam of clay runs close to the surface and appears along the shoreline right up the coast of Cardigan Bay. If there is a sandy shore or a shaley cliff there's likely to be a seam of clay to be found not far away But there's a big but- there's clay and there's clay. Much of the clay you'll find has a large percentage of sand or other particulates , and is unusable. It falls apart in your fingers when you squeeze it , it crumbles instead of squoozing.
So you have to find your squoozable clay , -sometimes it's revealed by weathering , storms , tides , or the way that clay makes the layers of soil resting on it unstable , so landslippage occurs revealing the grey stuff beneath.
This is a bagful I've just dug up.
It's remarkably useable as it comes out of the ground , there appears to be all sorts of organic material in there , but there's nothing that doesn't meld into the clay as you work it. It has a certain amount of sand that helps it hold together while it's being fired, and a fair amount of naturally occurring iron that makes the clay fire to nice pinky-red colours.
This is a pot made from virgin clay.
I want to find a way of processing the clay , cleaning it and making it consistent and then perhaps changing the variables I have at my disposal (adding more sand , toilet paper, -really!- or feldspar etc ), so I start by putting it through a sieve . This means working the clay as it comes out of the ground , squeezing it underwater between your fingers until it turns into sludge filled with globules a bit like frogspawn . This mess is fairly easy to push through a mesh with a wooden spoon so that you end up with a thick muddy slop . I use the fine mesh splatter guards you get for frying pans - they don't last very long but they are cheap.
The slop can also be made by allowing the clay to dry out to a leathery texture , then grating it into water with a cheese grater and letting it soak for a few days then putting through the mesh.
The third way is to let the clay dry out completely in small lumps , then crush it into even smaller bits and then add it to water and allowing to soak before meshing it.
Once you have a sieved slop , it has to dry out to the right consistency . Pour it onto a plaster batt , a sheet of plaster you can make by pouring some plaster into a big cardboard box . The plaster has to be very dried out before you can use it to dry your clay , it has to be dehydrated enough to suck the water out of your sludge. Other materials you can use are plasterboard or cementboard , or just a sheet of thick corrugated cardboard will do at a pinch.
You have to keep your eye on your clay to make sure it doesn't dry out too much , in hot weather in a dry room it can dry out enough in hours , in winter in a damper room it can take days. It has to be formable ,without being either so soft it collapses and sticks to your fingers or so dry it breaks apart instead of bending. When it's right it tends to just peel off the material it's drying on.
When you are firing the clay , the trick to dealing with clay that contains this amount of organic material seems to be to let the kiln temperature rise slowly and make sure it gets a good length of time at a temperature that burns off organic matter . I selected between 700 and 850 degrees Centigrade and let the temperature rise very slowly for an hour and a half over this range. Also let the temperature rise very slowly when passing up through the quartz conversion period around 570 degrees Centigrade , and the same on the cooling cycle.
I bisque fired to as high or slightly higher temp than the glaze firing , to give the clay a chance to move as much as it might want to before the glaze firing.
I made my kiln from a metal beer barrel lined with ceramic fibre . It wheels around on a shopping trolley and is front-loading. It's not a wonderful design , you could find many simpler and perhaps better ones on the internet. It's fired with gas from a canister. I've got a temperature monitor set up that cost me a few pounds on eBay , I'm not sure how accurate it is and I have yet to try and calibrate it using cones , but it's fairly consistent.
The glaze firing was a bit underwhelming.
I made the mistake of a) using glazes that needed a slightly higher firing temperature than I'd used for the bisque firing , and b) using up the gas in the can that was maybe enough and maybe wasn't , -it wasn't , and I ended up giving the pots the unnecessary stress of an extra firing to about 800 degrees and then fired them again later to about 1100 degrees to give the glazes a chance. At that temperature the iron in the clay that gives it the nice pinky-red hue turns into a dirty red-brown , and shrinkage cracks started to appear.
So , back to stage one. I found the sea had revealed a new area of clay yesterday , so I went down this morning and dug enough to last me for months. I hope it's as good as the other , it was close by so it could be.
FIRING #2
This is more like it. The big pot on the right is made with Raku clay I bought. The lid underfired because it was on the floor of the kiln. The one next to it is also Raku clay , but with a slip coating of the beach clay , hence the red /terracotta colour. The yellow one is beach clay with some (beach) sand added , and the left hand one is beach clay with toilet paper added to make a paper clay , fired with bits of rust scattered on the glaze inside as an experiment.
They were not bisque fired this time , just one slow firing up to about 1850 Farenheit. I think I was a bit timorous this time , I didn't want to overstress things so I didn't leave them to soak at the highest temperature as long as I should.
They all fired without cracking , and the clay turned this lovely red colour as I'd hoped.
So a bit more than a partial success . Now I have to experiment with different ratios of clay to sand , and try and hit the sweet spot in terms of temperature and time in the firing.
