I've been throwing larger pots recently and have had to put in some concentration as well as sweat. As I don't throw larger pots very often, I have to re-learn how to do it. This got me thinking that I should write down the little lessons that I learn and save myself some time in the future. Hence this post. These are based on my experience of throwing 10lb and upwards lumps of clay.
1. Make sure the clay is well kneaded and not too hard. This really helps when it comes to getting it centred. Well kneaded clay responds much better when on the wheel.
2. Centering - this is something that really takes a bit of muscle (see point 1 - clay that's not too hard). I try not to rush centering larger lumps of clay, you have to be patient. Keep the pressure on the clay using equal pressure with both hands - left hand from the side right hand from the top. Use the full spread of your hands. With larger lumps of clay I use my forearm as well! Be beligerent! You're the one in charge and the clay will eventually respond. The main thing is don't rush.
3. Opening - again you can't rush. Concentrate on forming the base of the pot. I tend to pull the clay out wider than I want the eventual base as when I begin to pull the walls up the base naturally gets narrower.
4. Pulling the walls - As with all pots, get the height first (don't rush). I've tried several ways of getting the walls to come up consistently from bottom to top. There are several techniques that you can use -fingers, knuckle lift, palm lift etc. I've tried all of these, but tend to encounter problems with the clay getting 'dry' during the pull causing an uneven pull. Personally with large pots I prefer to use a sponge in the right hand to ensure that the walls remain lubricated during the lift. As you make more pulls take care that the walls at the top don't get too thin - remember, you've still got to leave some clay to create the width! make sure that you're bringing clay up from the bottom, but be careful that you're not digging in too much at the bottom with your right hand. If the walls at the bottom become too thin they won't hold the weight of all of the clay above. Conversly, if the walls at the top become too thin then they'll fold. Leave plenty of clay at the top to make your gallery (if you're including one).
5. Add the gallery before shaping the pot. If you try to do this when you've made the finished shape then chances are the downward force that you'll need to apply when forming the gallery will cause the walls to buckle.
6. Form the shape of the pot carefully and always keep in mind that the clay at the bottom of your pot is carrying a lot of weight - pull it too thin and it'll slump. If it does start to lose its shape and you try to get it back into shape you'll more than likely cause the top to lose shape and at worse slump.
7. Know when to finish. Something i never seem to learn!
I'm sure that there are far better guides to making large pots, these are what seem to work for me.
I'll try to make a video and put it onto my youtube channel next weekend.