Sugar Skulls Mold: Part 1

Today I want to talk about one of my pet projects, or rather the virtue of researching your materials properly when you start working on a 3d project. Ever since I first heard about Día de Muertos, I wanted to get my hands on a proper sugar skull mould. I made one in plaster, but it was obviously cumbersome and a bit impractical. Over seven years later and I suddenly decided to start working on making my own versions March 2015. Since this is a private project, I have not documented it as well as I done with my school projects.

The aim of the project was to create plastic moulds that you could use to make sugar and chocolate skulls. I wanted the skulls to be a bit more detailed than the ones I found on internet and specialized shops. Anyway, during the Edition project I started to sculpt a skull in plasticine, which covered a golf ball core to ensure a relatively round shape. I knew that I needed to cast it in another material before I used the vacuum forming machine, but here came the first problem: you should not use plaster for plasticine, since the former exceeds the latter's melting point during hardening.

The obvious solution was to make a soft mould out of silicon. I went to Tiranti in London and bought some silicon and started to mix it in the plaster room. Unfortunately I was given a huge drill as a stirring tool and was told to hold it still for 20 min. As you could probably imagine, my hand got weak after seven min and I lost control. I accidentally grasped the drill trigger, which resulted in silicon sprays all around the plaster room. Angry and disappointed, I decided to restart the project and sculpt the skulls in clay, which were later cast in a huge rubber cast. This went far better and I managed to produce around 10 copies before I had to return the rubber to the Sculpture department. Here is one of few photos from this stage:

Several of my classmates enjoyed the designed and told me that I should make several and sell them, like blank templates that you could decorate however you wanted. Suddenly I took a huge detour by designing and experimenting with cheap package design, pattern, and logotype. In the end I only used the logotype anyway. While they looks good and all, I have only managed to sell one so far. Furthermore, it also stole focus from the mould idea I had going for me. I put the project to rest during summer, so I could return to it with fresh eyes at the beginning of the final year.

I tried to carefully saw into one of the plaster copies, repair the damage and put the halves through the vacuum forming machine, but the plastic refused to come off. It was painfully clear that I had not designed them properly, so I needed to restart a second time and redesign the overall shape. And since I wanted to work with two halves that were precise, I decided to try 3d printing. But before you can print, you must sculpt. And I have not sculpted anything in 3d since I studied game graphics.

I never managed to download the Autodesk Maya programme, so I settled on something less complex – Blender. It is a decent programme, but you cannot help but feel a bit puzzled when you are used to Maya’s tools and controls. Nonetheless, I managed to make a small model that we 3d printed in a small scale to adjust weird shapes, before I printed the halves in larger scales.

I finally had a model, so surely I could just waltz to the Plastic department and just print a copy? Not really. You see, at the time it was just a handful of students that experimented with 3d printing, which meant that the whole machine needed to be tweaked and hacked, from the brittle filaments to the software and adjusting of the printing area. All this tweaks and failures (including a power shortage) delayed the printing process with several weeks. I did manage to print it though, which was a deeply satisfying experience.

While I kind of like the low-polygon design, it turned out to be a bit problematic when I made some sugar skulls. The jaw was a bit too long and narrow, and the angular shape felt a bit too far removed from the Mexican celebration that started it all. I decided to smooth and sand the 3d-printed model with milliput to remove the angular shapes, which was later cast in alginate to make several plaster references. They would also be used for the vacuum forming.

After three attempts, it finally looked like I found my ideal shape. The question now was what kind of material I should use for the mould. HIPS is quite cheap and common material, but it is not food safe. I thought I had learned from my mistake by doing some material research on polypropylene. It is fairly popular since it is flexible, food safe, cheap, and recyclable. I bought four different sheets at online store Hindleys, which I had to re-cut to better suit our small vacuum forming machine. The problem was... None of the 3-4 books I consulted mentioned the slight trivia that polypropylene sags drastically and should almost only be used with aluminium-mould on an industrial level. This unfortunately lead to several costly mistakes later, one of which you can see below: