SLIP-CASTINGa ceramic forming technique

Slip-casting is a technique for small-scale production runs, especially for shapes not easily made on a wheel. It is the process of filling a plaster mould with casting slip (liquid clay) in order to create a clay object.

WHAT IS SLIP-CASTING?

• Ideal for producing hollow ware• Complex forms can easily be achieved• Does not require much finishing (usually only fettling)• Efficient use of material• Slip is fairly inexpensive• Lets itself well to small-scale production runs or limited editions

• Labour intensive• Slow production rate• Limited control over tolerances• Moulds may be heavy to handle• Large scale production requires many moulds, which them-selves require storage

Advantages

Disadvantages

http://www.sightunseen.com/2012/06/josh-bitellis-forfars-bakery-and-roadworkers-projects/ http://www.joshbitelli.co.uk/

SLIP-CASTING MANIFESTO

Come prepared Have a design in mind before starting and preferably some tools

You are going to get dirty Don’t be scared of getting dirty. Use your hands, get familiar with the material

Don’t be scared of making mistakes You are probably not going to get it right the first time. Experiment as much as possible as the best results often come from experimenting and making mistakes. Experience comes with time

You can’t learn “ceramics” in a week Don’t come expecting to learn everything there is to learn straight away. Take baby steps and focus on one aspect at the time

PROTOTYPE

MDF Easy to work and tool with, more durable. Prototype is safe and intact, great for achieving sharp, transitional lines and edges. Laminating together with wood glue might take a long to dry etc. but once it’s glued, it’s firm and stable.

Clay A model can easily be made with clay. It is preferable to allow the model to dry to the leatherhard stage before making the mould. You should preferably use a clay body that is similar in color to the work after firing it to avoid traces of clay of a different color in the final piece. This technique is not very exact in measurements so it’s ideal if you want a free hand product.

Blue foam This is a material that is relatively easy to handle and very light. It is quite expensive so use it reasonably. While moulding it is very delicate and can get scratches easily so you have to handle it with care. Otherwise it is ideal for more organic shapes that can be hard to obtain with wood.

Other A model may also consist of very soft materials such as mattress foam or textiles. However, during the construction of the mould, deformation may occur due to the weight exerted by the mould. The material can become compressed, resulting in staggered mould seams.

PLANNING MOULD SECTIONS

• Each undercut makes another mould section necessary (a curve in the form which makes it impossible to remove the mould section without damaging the form)

• Manageability of the mould is another factor determining the placement of mould sections.

• The weight of each mould section and of the entire mould

• The way the mould is filled and emptied

• How to hold together the different sections together (straps, tape or wires)

• Where to position your pouring hole

• How the mould is going to stand; its stability and strength (especially when doing multi-sectioned moulds)

One piece

Factors to take into consideration

Two piece or Multi-pieced

MAKING A CASTING MOULD

Free hand Use of cottes (device that holds the liquid plaster around the mould)

• Faster to make• Less waste of material• Irregular mould • May not be self-standing

• Longer to make• Use of more material• More refined look• Stable

CASTING

The slip is poured into a plaster mould, which absorbs the water leaving a layer of hard, leathery ceramic

The slip is allowed to sit in the mould until a desired thickness has been built up

The mould is then turned upside down and any remaining slip is poured out

The cast piece is then removed from the mould, fettled (trimmed neatly) and allowed to dry before firing

LEARNING FROM MISTAKES

BENJAMIN HUBERT - “Chimney Lights”

Benjamin Hubert conducts materials driven industrial design projects where the starting point of the process is the material or production technique. The studio challenges the everyday application of materials, traditions of construction and ideas of context.

The Chimney lights are produced using a technique known as slip-casting (liquid clay poured into plaster moulds) – they are cast with a white earthenware clay. After casting they are hand painted with a terracotta slip which has an addition of 25% sand – the painting process takes place on a potter’s wheel. They are then glazed on the inside with a white tin glaze and kiln fired. Each lamp has its own unique character with a textured exterior finish in contrast to a gloss white glazed interior.

http://www.hayonstudio.com

VALISSA BUTTERWORTH - “The Mod Collective”

Designed and made in Victoria, Valissa’s manufacturing process is a seamless combination of cutting edge technology and traditional craft practice that enables innovative investigations into non-conventional porcelain production methods and a unique product outcome.

Each concept is developed using Design software then printed on 3D printers in various mediums including plaster and plastic. Prototypes are moulded using a combination of silicones and plaster to obtain the final moulds for slip casting.

The creation of these moulds is a longer and more involved process than simple plaster mould making as the resulting moulds retain the intricate details the 3D printing process leaves in each prototype. These markings serve as a conscious and permanent reminder of the technology employed in their creation.

The next phase is traditional slip casting using coloured porcelain slip. Pigments are added at the liquid stage so the colour permeates each piece entirely, resulting in a depth of colour not able to be achieved by normal glazing. The pieces are then clear gloss glazed on both the inside surface and lip to retain functionality and fired to a vitreous temperature rendering them microwave and dishwasher safe.

http://www.craft.org.au/See/window-space/the-mod-collective/ http://themodcollective.com.au/

JOSH BITELLI - “Forfars Bakery Trophies”

Bitelli’s practice centres around the translation of research gathered from a given site into crafted objects. The history or provenance of a place becomes the foundations for an experimental de-coding, a type of story telling that narrates how things work, the people involved and the materiality of things.

Bitelli’s slip-cast Trophies not only pay homage to the 75th anniversary of the Forfars Bakery in Brighton, they also highlight the industrial machinery and mass-production processes that have allowed the bakery to remain competitive despite the changing nature of the bread business.

Taking a more hands-on approach, the designer borrowed some of Forfars’s product to create large bread molds into which he poured semi-porcelain slip, performing thousands of tests with different types of loaves.

“The slip had to be left for around six weeks to dry, and in this time, the surrounding bread grew some really amazing mold, I think because of the oxides and stains in the slip body,” he said. “I tried to copy this color palette in the finished vases.”

Bitelli was particularly proud of proving it was possible “to hack even the most standardized and safety-checked industries for the production of artisanal and crafted objects”

http://www.sightunseen.com/2012/06/josh-bitellis-forfars-bakery-and-roadworkers-projects/ http://www.joshbitelli.co.uk/

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