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AP1: Practical research - concrete sculpture


Within my practice I have a great love and interest in the material of concrete. I am very process driven and enjoy engaging with multiple workshops and trying to combine different processes such as metal work, 3D laser with more traditional plaster/concrete casting.


On my BA I had already begun to learn ways concrete casting, learning some basic ways of mixing concrete and plaster, the consistencies and making moulds and frames for casting. However, from this I wanted to push my work with concrete and explore other ways of creating images and compositions and really exploit the texture and aesthetics of concrete.




Experimenting with laser cut reliefs: Failures



Exploring fragmented shapes through laser cut outlines - developed skills using Illustrator through generating single line outlines from photographs.


Experimenting with acrylic pigments to add colour to plaster - found this a difficult process - hard to create a colour as have to factor in the added white pigment of the plaster - this lead to the colours being a lot more pastel than intended. Also I started by mixing the plaster and water and then adding pigment. This was very time consuming as the plaster was already setting and the process of mixing in the pigment caused the reaction to happen faster. This also lead to the pigments not being fully dissolved leaving streaks of colour and solid bits of powdered pigment inside the plaster. - after this I then learnt to mix the pigment into water first as this allowed the pigment to fully dissolve and also more time to perfect the colour before then adding the plaster.


Not happy with the soft texture of the plaster - too similar to the smooth finish of the acrylic - after this decide to mix in concrete to add more texture and contrast to the acrylic.


It was very challenging to get the quantities accurate - for this piece I did not mix enough which resulted in a very thin cast.


After making previous casts which had cracked in the mould I tested using mould release.


Using Vaseline - for this piece I did not wipe enough away - this left a noticeable texture on the piece which had to be sanded off,


Testing different finishing processes e.g. sandpaper, abrasive sponges - tights gave best result.






Experimenting using concrete - needed to consider the blue/grey colour and how this would impact the pigmenting. Also consider how much pigment is added as this adds a higher liquid content to the mix - in this case causing the mix to be too watery and reducing its structure.


When previously using pigments I had mixed the plaster/concrete first and then added pigment. This did not work for 2 reasons. 1 - it took too long to produce the correct colour which resulted in the mix hardening before being ready to pour. 2 - the pigment did not fully dissolve which lead to having solid pieces or streaks left in the set concrete. Instead I measured a quantity of water into bowls and mixed the pigment first, this allows it to fully dissolve in the water and gives unlimited time to test the colours. The only negative to this is that it is hard to see the colour and as well once the plaster or concrete is added it significantly changes the colour. The plaster brightened the colour turning it pastel which meant I had to mix much darker colours as I knew it would become lighter. After testing with concrete I also found that the concrete had a very blue colour which affected the pigment e.g. casing yellow to turn green when concrete was added. All of these changes had to be compensated for.


Using fabric binding to add strength - this was not pre-cut which led to time being wated and the layers of concrete setting which reduced the strength of the piece.


Piece removed from mould too early - led to the piece cracking - needed a higher content of plaster and concrete. The piece was also incredibly heavy. The mix was too watery due to adding large quantities of pigment as I failed to compensate for the increased in liquids due to the pigment also being in liquid form. After this I became a lot better at measuring out quantities and learning what the correct consistency of mix is.



Remaking and testing



After the first two tests broke I wanted to improve the design and remake the green cast. I also wanted to reuse some of the broken cast so decided to break apart the green plaster into smaller fragments to form a terrazzo. I was very inspired by Victor Seawards work and his use of the terrazzo process and it was one which I wanted to learn and develop. It also has a very loaded and significant history in terms of an architectural device in both Neolithic and ancient Rome structures, further linking to my interest in media archaeology.


I also wanted to improve the structural integrity of the cast so I opted to use wadding between layers of concrete. I also premixed my pigments using a higher quantity of plaster/concrete. This also allowed the colours to be more subtle and natural in tone. A significant change I made was the size. In the first green cast I felt like the shape was too constrained into widely used, produced sizes such as A0 and still very rectangular. I wanted more of an odd shape and opted for a slender slab more reminiscent of a monolith.


Negatives


  • The piece was incredibly heavy being solid and containing a much heavier mix of concrete.

  • The terrazzo fragments were not very well dispersed or close to the surface

  • Possibly too much terrazzo in the mix - caused fragments to protrude from back of the cast and had to be filed down.

  • Some of the melamine boards were warped causing the piece to not be square.



Second test with inset polystyrene



After remaking the first one and discovering how heavy it was I wanted to figure out a way of making the sculpture significantly lighter. I had already successfully made sculptures out of polystyrene which I had skinned with concrete, however I wanted to cast a piece with polystyrene inside.


For this I created the mould. I used a base of acrylic as this is very smooth and untextured and creates a similarly smooth finish on the cast. I constructed the walls using melamine, however one of these panels were warped so to fix this I inserted another sheet of acrylic to reinforce the straight edge. I lubricated all the surfaces with petroleum jelly, making sure to wipe it down with cloth to remove any streaks. This allows the cast to be removed without damage.


I then measured and cut sections of polystyrene board to fit inside the mould - making sure to keep enough gap for the mix to fill. I broke apart small sheets of cast blue/grey plaster to use for the terrazzo. Due to the plaster shards being porous they absorb water which will reduce the water content in the mix. To prevent this I soaked the shards in water, this also prevents them from floating in the mould. I then mixed two quantities of blue pigmented water, one to contain the terrazzo and the other just for a solely concrete mix. This was to prevent the terrazzo shards from sticking out the back of the cast which happened with my first test. I had to ensure both mixes had the same quantities of pigment so that the colours would match for both layers.


After casting the beige concrete into the black acrylic I then added the first layer of terrazzo mix. I tested using a plaster/mortar mix as the mortar contained small stones which added another textural layer, and was also more lightweight. Once this layer became firmer I set the polystyrene inside. Once this was in place I mixed another batch, replicating the sae amounts of plaster to mortar ratio. This was then flick coated into the gaps between the polystyrene and then a few cm layers added onto the back, completely encasing the foam inside.


Since the tests before had broken by being removed from the mould too early I kept the piece in place for a week, letting it significantly set and dry. Removing the cast I already found it to be significantly lighter. I was then able to use the scourer sponge as an abrasive to remove fine layers of plaster/mortar to slowly reveal to terrazzo fragments. By using a wet sponge it was less abrasive than a sandpaper and caused less scratches and with it being wet it also reduced the amounts of harmful dust from the concrete.


This piece proved to be very successful, both aesthetically in terms of the dispersion of terrazzo and colour palette but also in how well the foam was encapsulated. The piece was much easier to lift and transport and I felt more confident in having it wall hanging.