Topic outline

  • Introduction

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    • After a lump of clay has been centered on the potter's wheel, it must be opened up and the base formed. This tutorial will discuss this opening up procedure as well as showing you what to do when things go wrong. Much like this video, it goes over lots of little details about how and why certain things are done. In this detailed guide, we're going over one thing, and that's how to open up the lump of clay and form the base. A centered lump is our starting point.

  • Step 1: Positioning and Bracing

    • 1.1
      Every single piece of clay thrown on the wheel is opened up and a base of some kind is formed.

    • 1.2
      The fundamental premise is simple. Make a hollow in the lump of clay that differentiates the walls and the base of the pot.

    • 1.3
      With experience you can find center just by feel, but as a beginner it can help to create a spiral that goes inward.


    • 1.4
      You can easily create a small divot right in the middle so that you have an obvious target and so you know exactly where to push down.


    • 1.5
      But perhaps what's more important initially is the positioning of your arms and hands. Just like when centering the clay, you brace your forearm on the plastic of the wheel tray and lean your upper body weight slightly onto this arm to brace it. Make sure your fingers and palm brace securely around the outside of the lump.


      image

    • 1.6
      All this bracing and stability is incredibly important as if your movements aren't secure during this process, say they're floating up or you're only really using your thumbs, there's very little to support and guide your movements.

    • 1.7
      So don't let your arms or hands float.

    • 1.8
      Instead, and just like when you're centering, tuck your left elbow into your torso, squeeze your hand around the lump of clay, and make sure your arm is pushed against the plastic wheel tray.

  • Step 2: Opening Up the Clay

    • 2.1
      As for which digits to use to open up the lump, I use the thumb and my index finger. These two push down together, and as they do, I'm also controlling the base portion of the clay with my other fingers. They aren't squeezing in as much to center the clay, but they're there to keep the piece under control as I push down to form the hollow and open it up.

      image

    • 2.2
      As I push down, I make sure the lump of clay is well hydrated. The tip of my index finger is really taking the lead as I feel I can exert much more pressure with it downward. My thumb follows my index finger and helps to widen this initial hollow.

    • 2.3
      As I make this first hole, my fingers on the outside are squeezing in ever so slightly on both my right and left hand just to make sure the lump stays centered.

  • Step 3: Checking Base Thickness

    • 3.1
      You can now check the thickness of the base by removing any water that might be inside and sticking a needle all the way through until it hits the metal wheel head.

    • 3.2
      I then slide a finger until it hits the bottom of the well and then I draw the two out together.

    • 3.3
      The length of the needle exposed shows the thickness of your base.


    • 3.4
      For something like a mug or any other flat-bottomed piece, you should aim for about five to six millimeters in the base of your pot.

    • 3.5
      You don't want it to be too thin and weak, and when you wire the pot off from the wheel head, that removes about a millimeter or so of clay anyway, which needs to be compensated for.

    • 3.6
      Don't worry about the hole the needle creates; just run a wetted finger over it, and the hole quickly fills back up with clay.

    • 3.7
      Over time, judging the thickness of the base is something you learn to do by eye by comparing the level of the base on the inside with the level of the wheel head on the outside of the pot.

  • Step 4: Forming the Base

    • 4.1
      Sometimes you won't even notice that you've thrown the base too thinly, and then when it comes to wiring the piece off, you'll suddenly see a big hole in the bottom, which renders the pot useless.

      image

    • 4.2
      Although you can potentially fix this by removing most of the slip from the inside and then pushing a thick disk of clay slotted right to the bottom that's then compressed and blended into the walls of the pot.

    • 4.3
      Here's how I form that hollow from another angle.

    • 4.4
      I find the center point and then I push firmly down with my index finger and thumb.

    • 4.5
      My other fingers on the outside are squeezing in slightly, and I'm also linking my two hands together by resting my right thumb onto the back of my left thumb.

    • 4.6
      I then, with my thumb and index finger, draw the walls out perfectly horizontally towards my body, creating a defined right angle in the corner where the wall meets the base.

    • 4.7
      I then use the flat of my thumb to compress the bottom, smoothing over any lines that are left.

    • 4.8
      Depending on the clay you're using, lots of compression at this point can be really important as it can prevent cracks further down the line.


    • 4.9
      I then usually collar in the walls slightly to make sure they're perfectly centered and to make sure the walls are pointing upwards rather than splaying outwards slightly.

  • Step 5: Preventing Cracks and Ensuring Stability

    • 5.1
      As I pull the clay back towards me, I squeeze in less with the hands on the outside and I focus the pressure on my index finger and thumb, which glide over the base horizontally, forcing the walls of the pot out.

      image

    • 5.2
      This is all done in one gradual, even motion. I don't rush it or move my fingers sporadically.

    • 5.3
      If I feel any friction whatsoever, I'll quickly ladle in some water, as it's when the clay sticks to your hands that it is drawn off center.

    • 5.4
      If you do end up with lines like this, they're easily fixed.

    • 5.5
      I use my bendy thumbs and a finger, which push together and glide over the surface, compressing the base and neatening it.

      image

    • 5.6
      To do the exact same job, you can also use the pads of your fingers or even the flat edge of a rubber kidney like so, which leaves it nice and flat.

  • Step 6: Dealing with Lines and Adjusting Thickness

    • 6.1
      One really important thing to discuss is this corner in the pot.

    • 6.2
      If I'm making a straight-sided vessel, I make sure that this corner is pretty much a right angle.

      image

    • 6.3
      This way, you create a very clear divide between the walls of the pot and the base.

    • 6.4
      I'll show you what I aim for by cutting in half this centered lump of clay that's been opened up.

      image

    • 6.5
      You can clearly see the base section and the walls on either side.

    • 6.6
      This thick portion of clay around the diameter is the clay which I'm eventually going to pull up into the walls of the pot to a thickness that's ideally as thin as the base.

    • 6.7
      Another thing I purposefully do is to angle the walls at this point so they're facing inwards slightly.

    • 6.8
      That way, when I begin to pull the walls up, the clay is already in the direction I want it to travel.

    • 6.9
      Next, I'll show you a cross-section of what you want to avoid for mugs and straight-sided vessels, at least.

    • 6.10
      As you can see, the base isn't flat, there isn't a clear divide between the base and the walls, and the walls themselves are splaying outward.

      image

    • 6.11
      The main issue, though, is that by having a slightly curved base, you'll end up with a heavier base, as there'll probably be clay that remains in portions that you won't be able to trim later on.

    • 6.12
      More specifically, it's these corners, and I'm scoring the areas to show what kind of form I should have thrown it to initially.

      image

    • 6.13
      Unless you trim the inside of a pot thrown with curved corner, your pot will end up being bottom-heavy, as there's some material that would just be very difficult to touch, especially if you're throwing in closed forms like bottles or vases.

    • 6.14
      So once again, what I'm aiming for is something with clear defined sections.

  • Step 7: Correcting Off-Center Clay

    • 7.1
      If you don't use enough support on the outside as you're pulling out to form the base, there is a chance you'll lose control, and the walls on the outside can start to wobble.

    • 7.2 If you pull the walls too far out, they'll begin to overhang the initial lump we designated at the start when centering it.


    • 7.3 But just like you can center the clay at the beginning, you can also recenter the clay at this stage.

    • 7.4
      I do this by collaring the walls in either side to gain back control.

    • 7.5
      When I open it up again, I make sure I have my fingers clasped firmly around the outside to keep the walls stable as the base is formed.


    • 7.6
      If the walls are undulating really badly, I'll wet my hands and then tightly grasp the wall, like so, forcing the wet malleable clay back to being centered.

    • 7.7
      My fingertips are tense, and my forearm is resting on the plastic wheel tray, and I'm focusing on my fingertips and hands staying perfectly steady, as if the walls were wobbling like they were when you started this process, then of course the pot that you throw thereafter will have these same undulations, as any discrepancy at this stage will just become more exaggerated as the walls are pulled up thinner and higher.


  • Step 8: Different Techniques for Opening

    • 8.1
      This grip I use with my index finger and thumb is just one way of doing it, and the positions of my hands change depending on the size of the lump of clay.

    • 8.2
      But typically, this is what I do for this size.

    • 8.3
      Other potters will make a hole, raising both of their forearms on the wheel tray and plunge a few of their fingertips into the center.

      image

    • 8.4
      I personally don't like using this one because it feels awkward for my hands, and I feel as if it lacks support on the outside.

    • 8.5
      Then there's the classic method of plunging two thumbs into the middle and easing them out horizontally to form the base.

      image

    • 8.6
      Once again, I've just always found this technique quite uncomfortable, and I don't like that I'm exerting pressure in two different directions, whereas with the technique I use, both my finger and thumb pull towards my torso in the same direction, and my remaining fingers support the walls on the outside, helping keep the entire mass under control.

    • 8.7
      From a beginner's perspective, though, you should try all of these techniques, as you'll find that one might click with you more than others, and the shape and size of your hands will determine what feels best for you.

    • 8.8
      So experiment with them.

    • 8.9
      As long as you're sticking to the main principles of keeping your hands steady, gradually easing the clay out, and using enough water, anything will work.

  • Step 09: Opening Up for Bowls

    • 9.1
      So in this next part of the tutorial, I'll show you how I open up for bowls and for plates, as it's very different for both.

    • 9.2
      For bowls, I'll make my initial lump a little bit taller, and then I'll plunge in my finger and thumb as usual to create a sort of V-shaped indentation.

    • 9.3
      As for opening up and forming the base, that's it.

    • 9.4
      From this point, I'll begin to pull the curved walls of the bowl.



    • 9.5
      Another important thing to mention is that I've left a lot more clay in the base itself, which I'll show you in a cross-section.

    • 9.6
      My aim when making bowls is for them to have a very curvaceous interior surface.

    • 9.7
      I don't form a flat base whatsoever.

    • 9.8
      I also leave ample clay in the bottom, about a centimeter or a centimeter and a half, so that ultimately there's enough material to trim a nice tall foot ring from.

    • 9.9
      This again is something you can check by sticking a needle through the base when you first form the well.

    • 9.10
      The majority of the thick expanses either side will be pulled up into walls that overhang, and I'll just score in what a rough foot ring would look like to sort of demonstrate where the clay will be removed from later on.

    • 9.11
      There needs to be enough excess in the bottom to not only trim the foot ring from but also enough for the base of the pot itself, and an extra millimeter or so too to account for the clay that's lost when the piece is wired off.

    • 9.12
      Although this cross-section is deceiving somewhat, as the majority of the thickness in the wall here will have already been squashed upwards into the walls.


  • Step 10: Opening Up for Plates

    • 10.1
      As for a plate, the initial shape we begin with is much lower and wider, and the pushed-down lump sort of becomes the internal base itself.

    • 10.2
      For plates, I always use really soft clay, as it's much easier to squash down.

    • 10.3
      So with plates, once the clay is really centered well, I just keep pushing down.

    • 10.4
      For this, I use the side of my hand, the flat portion which is pushed firmly down right over the middle of the lump.

    • 10.5
      As I squash down, I'm applying most of the pressure from on top, but my left hand stays in place, the fingers controlling the outside, compressing inwards slightly to keep the edge nice and neat.

    • 10.6
      Once I'm content with the shape, I can begin to hollow out the lump, and I gradually ease it out from the middle with two hands working as one to thin it out a little bit and create just a small wall on the outer edge.

    • 10.7
      Although my hands are in very different positions from how I was opening up the clay earlier on, all of the principles remain the same.

    • 10.8
      My movements are consistent, the clay is well hydrated, and I'm trying to add as much stability to my hands as possible by bracing them on the wheel tray and on each other, and by tensing them too.


    • 10.9
      At this point, my fingers aren't just loosely gliding over the clay; instead, they're kept very rigid and they force the clay to abide by the shape I exert onto it.

    • 10.10
      Finally, I have my two different sections: there's the internal base and the slightly raised section, the wall around it.

    • 10.11
      As the walls of plates don't get particularly high, the majority of the weight of them is in the expanse at the bottom, and much of it will be trimmed away later.


  • Conclusion

    • In reality, the entire process of opening up the clay and forming the base should only take a few seconds. As for the wheel speed, it's often asked, and I typically spin quite quickly—not full speed but fast. The reason I've shown you various techniques at the end is to demonstrate that there are multiple hand positions and methods for opening up the clay, tailored to different types of pots. This technique is just the one I use, and I hope you can find something that works for you.
      The goal is to make this process of opening up the clay feel comfortable. If you find that holding your hands in a certain way is painful or awkward, like it is for me when I use two thumbs to open up, experiment and try other techniques until you find something that fits you. This is the joy of throwing pots on the wheel; no two potters do it exactly the same way. Our hands, arms, shoulders—everything used in this process—differ from person to person, making this craft unique and personal.

  • Source


    • The lesson is based on material from the YouTube video by Gadsby, F. For more information and analysis, the book by Gadsby, F. (2023), By My Hands, Penguin Books, is recommended.