bronze casting

Plaster Room 03/12/18

Weekly Summaries, Work in Progress

Today I got the third and final rose ran up, then attached to the cup with the rest using hot knives and wax. Then I painted a layer of shellac over everything, to help the grog to stick to it, and once it was dry I covered it all in first coat grog.

Once that had set we put the plastic cylinder over it all, and I layered scrim (netted fabric) and plaster along the bottom, to seal the cylinder to the board, and around the middle of the cylinder for stability. As soon as this was set I spent the rest of the afternoon mixing and pouring second coat grog, to fill the entire cylinder to make the mould ready for the kiln.

Really proud of my progress today! Got loads done, and worked hard to get the mould ready for the kiln. It doesn’t look like I’ll have a chance to pour before the break, but at least when I get back it will be all ready to go.

Plaster Room 26/11/18

Photographs, river project, Videos, Work in Progress

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Notes

  • Made up a batch of herculite for my hot rubber moulds- to demonstrate the process I am going to leave them exactly as they came out of the moulds
  • I made sure to wiggle the moulds as I poured to make sure the plaster got into every crevice
  • The bones came out beautifully but the brick broke as I tried to de-mould it, clearly the sides weren’t thick enough
  • I could make the brick solid instead of hollow but herculite is super heavy, and if I am trying to show the process it should be hollow to match how I made the wax cast
  • I will make a thicker hollow cast of the brick later on this week
  • I wanted to get into the metal workshop today but I felt really sick and foggy so Lindsey and I decided it was best for me not to use the power tools today. I didn’t want to waste a day, so that’s why I made the herculite casts, as a way to still be productive

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I also ended up going on a walk to the flower shop in Camberwell with Ellen, a BA Sculpture 2nd year student, and we are going to be doing some bronze casting together. We are both interested in nature, and capturing fleeting moments (and both want to make Christmas gifts for loved ones) so we bought flowers from the shop, and also collected foliage on the way back. We then dipped those in wax, and the next stage is to use a hair dryer to set the wax, and then we can build the moulds- the plants will burn out directly in the kiln so there is no need to make hot rubber moulds and waxes. The wax will help to stabilise the plants and make them a bit thicker, so that they will be more likely to come out in the pour. I know it isn’t directly related to one of my projects but this is something I’ve wanted to do for a while and I feel like I might as well give it a go whilst I have the opportunity.

Using an Engraving Tool on the Bronze Brick

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Process Video: Using an Engraving Tool from Kat Outten on Vimeo.

This short clip shows how I have been using an electric engraving tool to work details back into the surface of the brick wherever it was lost due to the casting process. The shiny parts are where I have used an angle grinder or Dremel tool previously to get rid of runners, risers, and other imperfections on the surface of the bronze. I have to take frequent breaks when using these tools, and swap hands often, as the vibration from the tool makes my wrists ache, but otherwise it is fairly simple to use. As always I follow safety protocol, wearing a visor, ear protection, dust mask, and gloves to protect myself, as well as having the extractor fan on and handling all tools safely and responsibly.

Applying the Patina

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A patina can refer to the natural colouration that happens over time to bronze, as the copper in the alloy reacts to oxygen, or it can refer to a man-made process where a chemical mixture is heated onto the surface of the bronze, to achieve different colours and effects. I am referring to the man-made process, and the above video shows foundry technician Becky Stevenson demonstrating how to apply a patina to one of my bronze pieces.

I then replicated what she had shown me, and once the pieces had cooled down I then applied two coats of wax, by hand using a cloth, to each piece to seal the colour.

This was definitely one of the more fun parts of the whole casting process! It was a chance to experiment and play with the different colours and effects that the application of heat and layering of the patina could achieve and I am super happy with how they turned out!

Removing Excess Metal from the Casts

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The photos above show the process and tools used for this stage of the project. As you can see I used a clamp to keep the casts in place whilst cutting and grinding off excess metal using a Dremel and angle grinder. I had to remove the cup, and all of the runners, risers and wax channels as they had all been cast in metal. This was hard work as the studio has been reaching 35 degrees Celsius, so I had to take frequent breaks and stay hydrated. On a few occasions the technicians closed the workshop completely as it was too hot to work in, and on other occasions I did the work in the metal workshop rather than the foundry as it was a few degrees cooler.

As well as removing excess metal I also used the Dremel and an engraving tool to work back in details that had been lost in the casting process, such as holes in some of the bones, and textures where they had been lost.

It took a bit of practice for me to get to grips with using a Dremel and angle grinder, as I had limited experience with only a Dremel, previously. However throughout this stage I learnt very quickly how to handle both tools properly and effectively, and I am really proud of myself for it- I have always been a bit scared of electric power tools but I pushed myself and am really pleased with how far I’ve come.

Before and After Clean Up Bronzes from Kat Outten on Vimeo.

The video shows the bronzes and aluminium pieces still attached to each other by the runners and risers, and then each bronze bone once I had finished working on them. As you can hear me say in the video I’m not 100% happy with each piece; I feel that the pieces of jaw both need a bit more work to add back in lost details around the teeth, and one of the bones in particular I want to go back and work into further as I am not happy with the hole (I broke two Dremel heads trying to fix it) or with some of the texturing on one side. However due to time constraints I had to move on to the patina stage, so that I would have some finished pieces to put in the end of year show.

Unfortunately I only had time to finish the bronze bones, so both brick casts and all of the aluminium bones will have to be finished when I get back from the Summer break. I am a bit disappointed by this, but the casting process is incredibly time consuming, and I want each piece to be the best it possibly can be, so I am trying not to beat myself up over not getting everything finished.

 

Cleaning Plaster From the Casts

Photographs, river project, Videos, Work in Progress

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Once the moulds had been poured and removed from the sandpit they next stage was to cut off the plaster coating, with a saw, and then smash open each mould with a mallet. The above photo shows one of the bronze casts, mid smashing. The aim was to remove as much of the plaster as possible, which was then smashed and ground up into powder, to be reused for further mould making.

This video shows part of the clean up process- once the casts had been removed from the mould, the rest of the plaster still needed to be removed from around the casts. It has been sped up by about 250%, as the original video was 20 minutes long, and I wasn’t sure if anyone would want to watch it! As they were too big to be secured in a clamp at this point I had to secure them with pieces of brick, so that they were stable enough to use the hammer and chisel on.

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Once I had gotten rid of as much plaster as possible with the hammer and chisel I tried to cut off some of the runners and risers using an angle grinder, which shook some more of the plaster loose. Before I could cut any more of the excess metal off I had to take them down to the print making studios and blast them with the pressure hose, not pictured because I got very wet!

Health and Safety: I had the extractor fan on, and wore gloves, a visor, ear protection, a dust mask and an apron

Prepping the Moulds for the Kiln/Setting up for the Pour

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Before the moulds could be fired in the kiln, Becky removed the plastic from the outside (that we had used to make the moulds, as seen in previous posts, and the brick video). We then had to cover the sides and bottom of each mould with layers of scrim coated in plaster, to create a protective barrier to stop the plaster moulds falling apart in the kiln- four of us did this, and I didn’t take any photos as it was very messy! But you can see the moulds with their plaster coating in the above photos. The moulds then went into the kiln upside down, as you can see in the photos. They go in upside down so that as the mould is heated and the wax inside melts it will flow out of the mould, leaving empty spaces where the metal will then be poured.
The next step was to vacuum the insides of the moulds to ensure they were free of debris, ready for the pour. Once this had been done the moulds were ready to be winched into place using the pulley system in the foundry, and set up in the sandpit ready for the pour.

The video shows the technicians winching one of the moulds into place, I kept out of the way for this part as I hadn’t done it before and wanted to watch and make sure I knew how to do it for the next moulds. I then had to dig the moulds in, making sure the sand was packed in closely around each mould to ensure stability for the pour. To keep the moulds clear each one had a piece of wood placed over the top.

This was definitely one of the more arduous parts of the process- it took five of us to do the plaster coating, and four of us to get the moulds from the kiln into the sandpit, as each one was incredibly heavy and fragile. I was careful to follow all instructions from the technicians to make sure nothing went wrong!

 

Process Video for Casting the Bricks

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I was worried that the process might be unclear from the step-by-step and photo posts, so  whilst making the brick moulds in July I recorded video clips, as well as taking photos, to better showcase the lengthy process behind casting in metal in the foundry.

This video shows the process of putting the wax bricks into plaster moulds, ready to be fired in the kiln. This stage was the lengthiest part of the whole process, and shows at least 3 weeks worth of work in the foundry- whilst waiting for layers to dry I was also working on the wax bones and prepping those using the same process, to make the best use of my time.

Unfortunately some of the clips are poorer quality than others as they hadn’t automatically backed up on my Google Photos, so I had to download them from my Instagram instead. Going forwards I am going to be much more careful about backing up my documentation. I was also a bit under the weather at the time of recording the audio for this video, so I am a little bit breathy, and stumble on my words a bit, which I have tried my best to edit out. This is actually the 3rd attempt at making this video, as the first and second time it didn’t save properly, but 3rd time’s the charm!

On another note, I am deeply sad that Becky, the foundry technician, has moved to teach at Chelsea as we got on really well and she has helped me a LOT with this project. Good luck at Chelsea Becky, we’ll (I’ll) miss you!

Putting the Waxes into Moulds

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These photos show the process of prepping my wax bones for the kiln.
Process:

  • I started by pressing the waxes into clay, separated by a layer of cling film to make it easier to remove the clay at a later stage. I built up the clay a little to help hold the waxes in place
  • I then joined the waxes to create runners (where the metal would flow through) and risers (where the metal rises out of) using wax tubes, straws, and sausages of soft wax, depending on the thickness of each bone. I added additional runners made of soft wax to any points on the bone that were smaller, thinner, or looked like they would benefit from it and joined them onto thicker parts of the bones or onto the main runners
  • Once I was happy with how the runners and risers and I had degreased them with meths (to help the grog stick) I then began to layer up the first coat grog mix (2:1 grog and herculite) starting off with a paintbrush to work it into the details of the bones. As the mixture thickened I then pressed it on and built it up around the waxes, making sure not to cover the main runners and risers (the pieces you can see sticking out)
  • When the grog had been built up enough and left to dry I then flipped them over, removing the clay and cling film, so that I could repeat the process of layering up the first coat grog
  • I then needed to extend the runners and risers further, bringing the risers at the bottom up to the top, layering with more grog as I went along, for support
  • As I did this Becky built up a base with grog, which we then used to stand up the separate parts of the mould, building the grog round the sides until it was stable
  • Next we had to get the cup onto the runners, using hot knives to join them and soft wax for additional support
  • Because of the heat we had to degrease and add more grog around the runners for support as we went, as we left one over night only to find that the wax had curved over in the heat
  • I then extended the runners using hot knives to join the pieces of wax tube, and bring them up to the top of the cup, again degreasing and layering grog as I went for support
  • The next stage was to fit a sheet of plastic around the whole thing, which we secured with duct tape, before mixing a batch of normal fine casting plaster. We then dipped some scrim into the plaster and used this to secure the plastic to the base- working extra plaster in to waterproof the join. We also tied some plaster dipped scrim around the middle of each mould to help stabilise it ready for the 2nd coat grog to go in
  • This isn’t shown in the photos but we then filled the mould gradually with 2nd coat grog (1:1:1 grog, ludo and plaster then 2:1 ludo and plaster) until it was to the top of the cup and left it to set

We made 3 moulds this way with the wax bones inside, but I will be uploading a more in-depth video showing the process of the two wax brick moulds once I have finished editing it!

Casting the Jawbone

Photographs, river project, Work in Progress

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Casting the jawbone raised a host of issues that I didn’t realise would be a problem, but hopefully it will work out in the end. Before we could make a hot rubber mould of the jawbone Becky (the technician) and I decided to make a plaster cast of the jaw, as we felt it would be too fragile to make a hot rubber mould from directly.

STEPS

  1. Before we could begin casting I had to fill in the holes in the jaw (where the rest of the teeth originally were) with soft wax, so that it would be easier to cast. I also used a little superglue to secure the two teeth- we were worried that they may have come out of the jaw when we de-moulded it, so this was a preventative measure.
  2. I then pressed the jaw carefully into some clay and built up clay walls around it, and then applied a few layers of vegetable oil to the jaw to help release it from the mould once the alginate had set
  3. I mixed up a small amount of quick set alginate which I poured into the clay mould and left to set
  4. Once this had set I carefully removed the clay and rinsed the jaw and alginate, before greasing it up with more oil, and building up clay walls around it
  5. Another batch of quick set alginate was then poured over this, and left to set
  6. The clay was then removed, and the two halves of the mould separated and the jaw carefully removed.
  7. After cleaning both halves of the mould I fit them together and secured them with elastic bands, and was then ready to pour fine casting plaster into it
  8. The first attempt didn’t work very well and only the thickest section of the jaw came out, so for the second attempt after pouring in the plaster I moved the mould around to encourage the plaster to flow through the whole mould
  9. Once I opened the mould up I realised one half had not worked out, and the other half, where all the detail was, was too thin- to fix this I cut up scrim and layered that and some more plaster on top of it until it was thicker and stronger
  10. I then de-moulded it and created a hot rubber mould from that plaster cast. Because the detail was lost on one side I decided to make a flat mould, rather than a round one that needed to be cut open, to save materials
  11. The final photo on the slideshow is of the original jaw, first failed plaster cast, second plaster cast, and de-moulded wax cast of the jaw- as you can see there are a lot of details that need to be worked back into the wax by hand, but I am confident that it is doable