The final stage of the sand casting was the most exciting because it involved heating up the aluminium to 600 degrees. The molten metal is pouring quickly into the mould after skimming the impurities off the top. The mould is then left over night to cool and harden. If you don’t let the metal cool probably and remove it from the the mould too quickly, it will break and the shape will change. This happens because to outside hardens quickly but the inner part of the mould is forming crystals which are very brittle until solid.
After the mould has solidified over night, we needed to bash the model out of the sand. I found it hard to get all of the sand out using a metal brush and a chisel but we were able to use a sand blaster. This is a machine which fires pressured grit at the work to remove sand which is embedded into the metal. However, I decided not to use it because it gives the metal a mate grey texture which I didn’t want. My tutor recommended I wash the sculpture to soak the sand out. My work did resemble an ants nest but not as much as I wanted. But it did remind me of a very complex maze with different paths similar to those women took to get the vote including hunger strikes, protests, hanging their bras in public and more extremely, jumping in front of horses.
After talking to my tutor I decided to edit the polystyrene mould more using the hot wire in the soft model studio. I started to experiment with the hot wire and the mould started to replicate an ant nest. There are many videos on social media of liquid metal being poured into dormant nests forming incredible casts. I wanted to combine this idea with the initial idea of my current mood and stress levels. I made holes and bumps in the mould to represent the unevenness of my emotions and the obstacles I have to overcome to finish my degree year successfully.
We needed to make a box to hold the sand and the mould. In order to use as little MDF as possible to prevent wastage, the tutor recommended to have a two-finger gap. This left enough space for the sand to surround the cast but to stop the overuse of sand and MDF.
The induction into the sand mixing and and packing it around the polystyrene mould. We used carbon dioxide to dry out and compact the sand into all of the holes in the polystyrene to get as much detail as possible. After filling and and compacting the sand using a wood hammer I was required to make holes through the sand using a metal wire. By turning the Carbon Dioxide extinguisher on through the holes would allow it to seep through the sand. The purpose of doing this is to speed up the drying and hardening process. Once this was completed it must be left for about a week to set properly.
Sand casting is a process used for metal casting. It uses sand as the mould. Sand casting is made up of 4 basic steps:
- Assembling the sand mould
- Pouring in the liquid metal
- Allow the metal to cool
- Break away the sand mould and remove the castings
Green sand casting is a common method of casting which uses wet sand. It is classified as ‘green’ because the sand does not set when the molten metal is poured in.
After the induction we were given a piece of polystyrene to create into any shape we wanted. The shape we make would be of what we want the final outcome to be made of because you use the polystyrene to mould the sand into the correct position. I tried out many different shapes using only one piece of polystyrene to experiment and develop my ideas as I work. This is something I haven’t really done before but as I didn’t have an initial idea I thought it would be a great way to finalise my mould. I formed a rough shape with many patterns and indents which sort of represent my life at the moment. I have a lot of university work and a social life to uphold which is causing some stress and making me feel a little crazy which has influence this piece.
Pros and Cons of Sand Casting
- Easily recycled – can reuse the moulds
- Withstand extreme high temperatures
- Poor surface finish
- Complex design
- Long setting and drying process (before the pouring of the liquid metal)
The day started with a detailed induction of a range of different techniques to cut, texturise and change the shape of the clay.
The techniques we were told:
- Kindering or stretching the clay by throwing it in a diagonal direction onto the table top. This allows the clay to stretch naturally and allows you to distort any groves and marks you may have made beforehand.
- You were able to cut groves into the clay and then insert some ball clay – dried white clay – which creates a marbling effect
- Cutting profiles to create shadows – we were recommended to start with subtle profiles and then add as you go along.
- Slip clay can be used create texture on the clay. We used white slip on the Terracotta (a red-orange clay). Before applying the white slip, you needed to make groves in the terracotta clay and then apply a thin layer of the white slip was to be brushed over the top of it.
- We were told how to make slabs of clay which was quicker to dry. The drying out of the clay means it will be stronger and easier to mould. The slightly dried clay would be able stand up freely. Today, we didn’t have enough time to dry the clay out so it wasn’t as sterdy as the piece used in the demonstration which had been cut the night before and left over night to dry out.
- Screfetto is a technique where you apply white slip over the terracotta clay and then scratch away at it to create groves and marks.
- The most important technique I was taught was a way of joining two pieces of clay together. You needed to key or score in a crosshatched manner, the sides of the clay that you want to stick together. Then you would use some watered down terracotta clay as glue on both sides to stick the clay together.
We were inducted into the band saw, hand drill and sanding machine today in the wood workshop by the technician Nigel Williams who provided us with a detail breakdown of how to use the different machines and the health and safety which came with them. He provided us with stories which made us think about using the machines correctly to avoided injury!
We were given a piece of MDF board to try out the band saw and sanding machine and had to cut a curve and a straight line using the band saw and sand down the edges using the sander. By doing these exercise we were able to get signatures in our passports which allow us to use the machines without the technicians.
From this exercise I am now able to use the machines freely and safely throughout my degree to create sculptures for projects.