Approaching the making process, I split it into six main stages:
- Sculpting
- Moulding
- Casting
- Chambers
- Puzzles
- Painting
While some of these stages had to be completed before I could move on to the next – for instance, I had to have a cast of the shell to create the walls for the chambers – they didn’t follow a strictly linear pattern. I planned so that I could be completing other stages while moulds were curing etc.
Following are images of each stage, with short descriptions of problems encountered and how they were resolved.
Sculpting
To start off with, I had to make the ammonite shell that would be the main body of the model. I used buff clay as it is very quick to sculpt with due to its softness.
For reference, I used an image from The Etches Collection of an ammonite in their collection.
I explored making a stand for the sculpt at the beginning in order to allow me to sculpt both sides of the ammonite. However, I quickly realised that this would not be needed as only one side would be visible. Therefore, I could rest it flat on the desk.
Sculpting the ammonite was a relatively straightforward process that was quick to complete.
Along with the ammonite shell, however, I also needed to sculpt the head and tentacles of the animal. I did not want to use buff clay for this sculpt, as it was on a smaller scale to the shell and would need more details. The tentacles would also pose a problem – due to the softness of the clay, they might be prone to moving while I sculpted, even with an armature inside. Consequently, I decided to use Monster Clay – a harder material.
I could not use Monster Clay alongside the buff clay due to the difference in softness, but I still wanted to make sure the head fit snugly into the opening of the shell. To achieve this, I held off sculpting the head until I had a cast of the ammonite shell I could sculpt into.
For reference, I used images of cuttlefish and nautilus.
Moulding
After sculpting the ammonite shell, I created a mould of it using silicon. As the back would not need any detail, I could make it an open back mould.
During this process, some silicon seeped underneath the shell as it was not flush flat against the surface. I cut out the unnecessary silicon.
The head and tentacles of the ammonite had to be moulded in plaster, as I wanted to cast it in silicon later. Due to the complexity of the tentacles, the mould had to be made out of two parts.
I encountered one particular issue while moulding the second part of the plaster mould. While I made sure to plug any gaps between the styrene walls and plaster, there must have been a gap I overlooked! Some of the plaster seeped underneath, which caused the risers on that side to be covered up.
To resolve this, my first idea was to attempt to dig the risers out of the plaster once it had hardened. I quickly realised this would not be an effective way of solving the issue, therefore I decided to amend my casting process for the head and tentacles instead.
Casting
I used the silicon mould to cast copies of the ammonite shell out of fast cast resin. There were a few problems I encountered during this process.
The main issue that arose was the weight of the cast. For the mechanism to function effectively, the shell could not be too heavy, as it would impact the type of spring strength I would use. The heavier the shell, the higher strength of spring I would need in order to prevent the shell sinking straight to the bottom once placed on the spring. At that point, the puzzle pieces would not make an impact on the vertical position of the model as it would already be sitting on the bottom of the spring!
Unfortunately, I realised this was an issue after I did my first clean-out cast and felt the weight of the shell.
To resolve this, I used aluminium trihydroxide powder. The theory behind this was that the powder would replace the resin in the mixture, which would result in a lighter cast. I tested this out using my second cast – it did not make it lighter. In fact, it had the opposite effect, and made the cast even heavier!
A positive of alumiunium trihydroxide powder is that it results in a far more durable cast, so I decided to use the shell from my second attempt despite its weight. I could lighten it afterwards by taking away material from the back.
Another issue I encountered during this stage, was in relation to the magnets I planned to place in the chambers of the ammonite that would help to keep the puzzles in place. Initially, I planned to place the magnets in equal distances from each other on top of the silicon. In practice, however, this did not work – the magnets were too close together and attracted to each other immediately. To counter this effect, I poured the resin in layers and placed a magnet in each layer. This meant that the magnets were held in place as the resin cured.
While casting the silicon head and tentacles of the ammonite, I also run into some obstacles. As mentioned previously, half of my risers were accidentally covered during the moulding process. To avoid bubbles forming inside the tentacles, I did not pour the silicon into the closed mould at first. Instead, I left the two halves open and filled the tentacles. Afterwards, I closed the mould and used the vac chamber to get rid of any potential air bubbles. Lastly, I injected the rest of the silicon. This solved the issue and no bubbles formed inside the tentacles.
Chambers
Firstly, I used paper to make some quick prototypes of the shape of the walls. I used these shapes as reference when I heat bent chemiwood for the walls. I used a jig – a secondary piece of chemiwood which I sanded down to the desired circular shape – to ensure the walls had the correct shape.
Using filler to create a plug for the chemiwood to stick inside the ammonite chambers was a bit tricky, primarily due to the sanding afterwards. Some of the areas were a bit tight and it was difficult reaching them. I tried using a rotary tool to get to these areas but the tool was too big. I resolved this issue by just spending more time sanding.
Puzzles
This was perhaps the most experimental stage of the entire making process. I encountered numerous problems as I explored how much weight I could add to resin.
I originally thought about using metal powder to weigh down the puzzle pieces, however, after researching some of these powders, I decided it would not be a cost-effective option. At this point, I considered the casting of the shell that I did earlier and remembered how the use of aluminium trihydroxide powder increased the weight of the cast.
Unfortunately, due to the size of the puzzle pieces, the powder on its own would not have made enough of a difference in terms of weight. Therefore, I considered other options and explored placing different objects inside the cast to weigh it down. I settled on using steel nuts, which combined with the aluminium trihydroxide powder, considerably increased the weight of the cast.
At this point, the steel nuts became an issue for me – they were extending out of the cast and very visible. To resolve this, I did a layer of resin around the mould, let this cure, and then placed the nuts inside. This ensured the steel nuts were not visible.
Frustratingly, casting a layer of resin around the mould first to hide the steel nuts, manifested another problem. The aluminium trihydroxide powder I was using, caused the resin to cure much slower. As I had to continually turn the mould to coat all the walls in an equal amount of resin, the increased curing time meant I was turning the mould for an unnecessarily long time. Consequently, I chose to use purely fast cast for the outside shell layer, which cured much faster. I still used the powder to bulk out the inside layer of the cast.
A final issue I encountered was when I was dying the resin. The multiple layers of resin meant I had to ensure that they all had the exact same shade of blue. I was forced to spend extra time while mixing the resin each time to match the shades. Unfortunately, this meant that the resin would start to cure by the time I would get the shade right. To resolve this, I made note of how much of each pigment I was using per 12ml of resin (the average amount per layer) which helped to mix the right colours much faster.
Magnets were also added to each cast to correspond with the magnets placed in the shell.
Lastly, some interesting notes from this stage:
- The alumiunium trihydroxide powder made the resin more gooey for longer (due to the slower curing time). This meant that bubbles were more likely to form in my puzzle pieces as the steel nuts trapped some air inside. The effect of this can be seen in two of the photos below, where a large air bubble formed at the top of the mould.
- The difference in curing time was particularly obvious in one of the below casts. I took it out of the mould too early, which meant the inside layer containing the powder was still fairly gooey. This cast highlights the two different layers of resin – the shell and the bulk inside.
Air bubble forming on top of the mould 
Evidence of different curing times 
Painting
In preparation for this stage, I kept my first cast of the ammonite shell to use as a tester. I used it throughout to experiment with different colours and airbrushing techniques.
For paint to adhere to the surface of the shell, a primer base was necessary. I tested my primer on the tester shell and realised that it would result in a cold underlayer. It also affected the paint that would go on top – it added a green tint to the yellow base coat. I used a white primer on the shell instead.
I used acrylic paints and an airbrush to paint the model. I painted the eyes and highlights with a small brush.
One of the biggest issues I encountered during this process was right at the beginning – while spraying on the first coat of my base colour, I realised the paints I was using had hardly any pigment in them. This meant that I would need far too many layers to even get a faint colour on the base. I used different paints and this issue was solved. (Pro tip – always test the pigmentation of paints!)
To build up enough pigment, many layers of airbrushing were needed. I had limited time left to apply this finish, which meant I could not get the amount of detail I initially planned to paint.
Finally, while painting the eyes of the ammonite, I found it particularly tricky to use the airbrush. Despite changing to a 0.2mm nozzle and needle, and decreasing the air pressure, I continually ended up with a ‘spidering’ spray pattern. I hand-painted these areas instead.
Tester shell 
Overall, the making of this model was very exciting, with its fair share of frustrating moments! I enjoyed each stage in its own way, and wish I could spend a little bit more time exploring each one in more detail.
Alicja Makes 