Plaster LathePosted: October 25, 2014
The sort of bowl shaped plaster chuck is placed on a clay board or bat and held in place with plastic clay around the thread and under the shoulder of the bowl. A wall is then constructed around the chuck, this is made from a 1mm thick sheet of plastic into a cylinder and held in place by two strings top and bottom. Around the base of the plastic cylinder press a thick sausage of clay and smooth it onto the plastic and the bat creating a seal all around. Its worth spending some time getting the cylinder as straight as possible, this means less work centring later on and less plaster wastage. A small amount of clay can go around the inside of the plastic cylinder tube where the wall meets the chuck metal collar and rub it smooth, this stops plaster going where it isn’t wanted. Good plaster for turning is Prestia Plaster, it is finer quality than potters plaster, mix 950g to a litre of water. It take’s longer to go off than potters plaster so leave it to soak – or ‘slake’ – for 2 minutes before mixing. Scoop off any surface bubbles then pour evenly and in a controlled way into the chuck mould.
Take a wrench and lock the chuck drive shaft to make it easier to load up the plaster chuck. Turn the plaster next to the chuck shoulder to make a neck, make this a few cms deep and wide – this is preparation for when it comes to cutting your work off the chuck.
Once the chuck is loaded and a collar has been carved it is time to centre the plaster. Un-centred plaster has a very visible wobble, centred plaster runs smoothly with no wobble. Move the tool rest as close to the plaster as you can without the spinning mass hitting the rest. Place your tool on the rest bevelled side down, using a pointed tool push the tool in to the plaster a couple of mm all along the length of the plaster several times until the whole mass has lost several layers and the wobble disappears. Smooth out the plaster mass with a flat edged tool and begin creating the form you want.
Continue to keep the tool rest/guard as close to the work as you can throughout the lathing process.
On my first chuck I improvised two forms, just visualising a shape in my head and then doing my best to realise it in the spinning plaster. Its very satisfying to work, its very immediate and pleasing to watch your form unfold and evolve. The second chuck I worked was inspired my some quick drawings and exploratory sketches I had done the night before, so as to have an idea of what I wanted to make and to try making something I had premeditated rather than improvising.
So far from my small amount of experience I have found that I use the different tools as so:
- Pointed – centring, deep thinner lines, deep ‘v’-shaped grooves, fast rough shaping.
- Flat – Smoothing centred chuck and shaping, softening shaping by pointed tool and for making large bold lines, trenches and curves.
- Round – Smoothing rounded forms and for necks, fluted mouths and form interiors.
- As my experience grows so shall my knowledge of lathe tools capabilities and alternate uses. Next time I want to experiment with using both a rubber and thin steel shaping kidneys to shape curved and rounded forms.
Further development from here ; more chucks and slip casting turned pieces, just build up experience and try and create some forms to slip cast and then sell….