Press Moulding

Last week I tried to make my own press mould for the first time, not very successfully. My plan is to create press moulds from composite thrown forms so I can build them together into large sculptures. I find it easier to hand build on a large scale with grogged clay, but it’s painful and not very effective to throw with heavily grogged clay, so I will create press moulds of the thrown objects instead. These forms will be for my final individual project . I’ve narrowed the brief down to explore the imagery of in Italo Calvino’s ‘Invisible Cities’, Ch. Thin Cities 3, especially the idea of a network of pipes as underground veins…

“Whether Armilla is like this because it is unfinished or because it has been demolished, whether the cause is some enchantment or only a whim, I do not know. The fact remains that it has no walls, no ceilings, no floors: it has nothing that makes it seem a city except the water pipes that rise vertically where the houses should be and spread out horizontally where the floors should be: a forest of pipes that end in taps, showers, spouts, overflows. “

I began by bisque firing a form I’d constructed from thrown sections then made a two piece plaster mould of this. The ceramic got stuck in the plaster when I tried to release it, either because I hadn’t used enough soft soap or because I hadn’t placed the middle line in the exact centre.

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Since for press moulding it doesn’t matter that the plaster is completely sealed together (unlike slip casting), I used glue to stick the broken plaster pieces together.

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This afternoon I’ve been making press moulded shapes ready to start sticking them together tomorrow to build large lattice structures.

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Alongside these I’ve been throwing functional ware for the anagama firing we’ll do at Naas in a couple of weeks. These 500g bowls are a little on the heavy side, I’m still a little afraid I’ll turn off too much clay and end up with a hole. I’m been experimenting with the angle and depth of the footrings to see what looks best…

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Alien Shells

These forms above where made by casting plaster (2:1 plaster to water ratio) into thrown vessels with the technique described here. Red and black iron oxide was used to dye the plaster and the yellow surface effect is the result of using yellow earthenware clay to cast into. I enjoy the surprise of finding the hidden inside form within the clay once the plaster has set, it’s always a mystery to what form it will take. These plaster casts are fragile, they feel like eggshells to hold. I prefer the more complex asymmetrical forms like the one at the top of this page – it looks alien. The smaller pieces that fell off look a lot like shells. The pink one is also interesting, the controlled, smooth inside of the thrown vessel becomes the outside and the inside is changed to the very gloopy looking texture of plaster halfway to drying. It looks like the inside is alive, spilling out onto the outside.

It would be possible to make moulds from these moulds and complete the circle with a slipcast ceramic object which had the original’s inside form on the outside. Simpler, symmetrical forms would probably be best to try out first though.

Plaster casting and Mummified Space

Initially interested in how a vessel can hold light, this project has taken a turn and I now find myself investigating the space inside the vessel. Inspired by British sculptor and Turner prize winner Rachel Whiteread I have begun to cast plaster into my thrown constructions with the hope this will create an extra layer of distance from the original object, rendering the invisible visible and bringing form to something which was originally intangible.

In her 2014 essay ‘Loss and Melancholy in Rachel Whiteread’s Casts’ Sheyda Porter compares Whiteread’s work to Freud’s definition of ‘the uncanny’ because of the way  ‘it refers to something unfamiliar arising in a familiar context and vice versa. ‘ She goes on to explain how French psychoanalyst Jaques Lacan defines the uncanny as ‘the very image of lack’ – and what better way to describe Whiteread’s work, turning the inside out and giving form to the void? I hope by using a similar technique I can turn my thrown objects, which show clearly how they have been constructed, into more intriguing objects of mystery which show the part of the vessel you can’t usually see. Porter quotes from Slovenian philosopher/psychoanalyst Salvoj Zizek ‘instead of the vase embodying the central void, the void itself is directly materialized. The uncanny effect of these objects resides in the ways they palpably demonstrate the ontological incompleteness of reality: such objects by definition stick out, they are ontologically superfluous, not at the same level of reality as “normal” objects.” ‘. The whole essay can be found here.

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‘One hundred spaces’ -resin casts of the space underneath chairs (1997) by Rachel Whiteread. Image source:

The process I used means lots of the plaster leaked out. As a consequence the negative form of the vessel’s void also has an inside and outside:

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Form constructed with thrown sections then supported with extra clay. Plaster was poured in the top.
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Once the plaster was set, I destroyed the clay shell around it, feeling like an archaeologist discovering a historical artefact in the ground. The original form is destroyed and the resulting object becomes a ‘memory’ or a ‘ghost’ of the original.
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The plaster form inside shows the throwing ridges that are a negative of the ones on the original thrown form. I’ve been told it looks like a component of a steam engine. 
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I didn’t leave the plaster to set long enough so the outgrowing plaster sections fell off
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The holes in the vessel introduce light into the dark interior.

I was disappointed when the smaller plaster sections fell off, next time I need to be less impatient and let the plaster dry properly before removing the clay. Large air bubbles in the plaster meant lots of the detail got lost too. Interestingly though, these smaller plaster casts reminded me a lots of fossils when I felt them in my hands. Sheyda Porter describes Whiteread’s sculptures as ‘mummified’ space. Similarly fossils are traces or impressions of something that was once living, the soft tissues decompose leaving hard bone and shell which are covered in sediment which hardens into rock over time. Once again, I find myself returning back to the theme of memory.

Field: Development into 3D

In my tutorial with David last week we discussed colour theory and the way putting colour on the back of flat planes can reflect the light in a halo of that colour around the edges. As an example he suggested I look at the first year fine art project displayed on the third floor – I hadn’t looked closely enough at these to notice the optical effect before but it makes the images pop. I glued some coloured paper to the back of my cardboard cutouts and the result above shows a very subtle halo of green and red light shining behind them. It reminds me of the hazy reflection of light you get on overcast days like the ones we had at Port Eynon. If I manage to make some of these in porcelain paper clay I could glaze the backs to get a similar effect.

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After Laura’s plaster casting workshop I was keen to try printing onto plaster because I hadn’t tried it before and I saw the opportunity to make more slab-like forms which I could assemble as a kind of theatrical scenery. I rolled coils of clay and pressed these onto an inked up plate, creating walls around different sections. Next I poured in plaster to a thickness of about 1cm and reinforced the back with scrim. I mixed up two lots of 2 pints water/plaster so I didn’t have to do the whole plate at once. I should have been much neater with the clay by cutting walls from a slab because I would have had to file down the edges less this way. The resulting sections are a bit too thick – maybe I could have poured the plaster sooner. On the plus side, lots of detail came out from the intaglio plate.
I then set these upright in a bed if plaster (4 pints) which again, was poured a bit late so looks like icing slapped onto a cake with a palette knife. The scene looks a bit naff and reminds me more of a snowscene with ice and glaciers than a beach. I like the idea of placing a second inked up plate onto the drying plaster then hanging up the sections when they’re dry so the print is shown on both sides.

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I also tried using coloured slips and sgarffito on slabs of clay. Inspired by Morgan’s Vicarious Wednesday talk I tried using paper resist stencils but discovered I have very little patience when it comes to decorating. Hopefully the slabs below will fire black and white.

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Slips brushed on White St.T

I’ve also been working on making paperclay for the first time. Porcelain casting slip can’t be used for this purpose so instead I had to use porcelain from a bag. I dried out the clay then ground it to a powder in a pestle and mortar, added water, then let it slake down overnight. In the morning I poured off excess water and soaked the paper pulp (ratio of 1:3 to the clay) for 2 hours before sieving it (60 mesh) to get rid of excess water. I mixed the paper and slip together by hand but the consistency was very lumpy so Matt showed me how to use the glaze mixer which blends the paper pulp into a smooth consistency.

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Sieving the slaked down porcelain before adding paper pulp
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Glaze mixer

I made up an ink with black underglaze, a small amount of borax frit to make it less powdery (about 5% is ideal) and copperplate oil. The powders were sieved through 200 mesh then the oil was added gradually, applied to the plate and rubbed off with scrim the same as with the intaglio ink. This afternoon I built a wall around the plate and poured in the porcelain paperclay slip with the hope it will be dry by tomorrow with the ink printed on. The underglaze should stay on when fired but it will need a transparent glaze to seal it. I’m worried the clay might not dry in time for tomorrow’s assessment so I may try using a heatgun to speed up the process.

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Inking up the plate