This post is in response to queries on how to throw large items similar to the water filters.
Begin with a suitable size, 4 - 5 kgs. It is easy to work and stands up well with a 10-12 mm wall. This means thrown sections will need joining to create wanted size.
The joint I use is a ‘V’ joint shown in (fig1). The tool I made is from an old credit card (you could use the current one) shaped as shown. (fig2)
With the ball of clay at a size of your choice throw the base and wall to height as far as possible with a 10 - 12 mm wall. Throw this on a batt so you can remove it from the wheel.
You will need a source of heat, electric heat gun or better still a gas blowtorch. These are available at your hardware shop.
With the blowtorch dry your thrown piece to a point where you are confident it will hold the weight of the next section. Trim the top off level and form an upside-down V. = /\ with your new tool. (fig3)
Take this part including batt off the wheel and begin again on another batt.
This time throw a cylinder with 10 - 12 mm wall thickness.
Using calipers make the top of your cylinder the same diameter as the first section.
Use tool (fig 2) to form ‘V’ in the top edge and use heat gun stiffen top half of the cylinder .
Adjust diameter as there will be some shrinkage due to drying slightly from stiffening.
Measure the diameter at the top point of the first section; and bottom of the ‘V’ on the second section. (fig4)
SECTION THREE (the tricky bit)
Remove the current cylinder, including batt, from the wheel and replace with the first section.
Brush slip on top of the inverted ‘V.’
Using a third batt turn over section two. Take hold of the batt (bottom original batt is now on top) and place the cylinder on top of the base. They should fit if you measured correctly.
Cut the batt off the top cylinder using cutting wire.
Blend the join by using two straight wooden ribs. (fig5)
Now pull up the rest of the clay to thickness 10 - 12 mm.
Level top of the cylinder and start again on the next section as done in section 2.
Depending on what shape you want, this is the time to begin shaping sections one and two. When satisfied with the shape use the heat gun and stiffen the bottom section. (fig6)
Continue with sections until you reach your wanted size.
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