Cthulhu is a character created by the writer H.P. Lovecraft. In The Call of Cthulhu, it is described as “A monster of vaguely anthropoid outline, but with an octopus-like head whose face was a mass of feelers”. A sketch of Cthulhu by Lovecraft shows the monster sitting hunched over in profile, tentacles tumbling from its face. The striking image of this strange character has become something of a pop culture phenomenon, with many artists creating their own renditions over the years. This gave me a wealth of reference material to draw from when it came to designing the mask.

Although Cthulhu as a character has a very specific appearance, the challenge for me as a designer was how to visually link Cthulhu to the world of Pomona, and design a version that felt unique to the play. In that context, the objective was to create a frightening, haunting figure that represented the fear and chaos at the heart of the play.

I wanted the colours and textures of the Cthulhu mask to reflect the urban dystopian wasteland depicted in the play, as though the creature had risen up from cracks in the damaged concrete island; as though Cthulhu was born out of Pomona.

I outlined these ideas in my initial sketches, which were discussed and agreed in collaboration with the writer and director. In terms of making the mask, my process was to first create a clay sculpt based on the sketches, then cast it in plaster to make a mould. This plaster mould was then used to cast the final latex mask.

I began by making a rough mock-up of the head of the main actor who would be wearing the mask out of newspaper, on a sturdy wooden stand. Then, starting with a small lump of clay, I covered the newspaper and built up with layers of clay to create the overall shape of Cthulhu. I then refined the sculpt to add smaller details, such as the eyes and ridges on the head. To create the tentacles, I stuck a handful of clay onto the sculpt’s face and kneaded it down into the right shape, adding more clay as was necessary.

The tentacles were one of the biggest technical challenges at the sculpting stage. The snout and tentacles were heavy, and protruded from the face. This meant there was a danger of them breaking apart from the rest of the sculpt. Because of this, I decided to reduce the size and shape of the tentacles from the original sketch, to make them more feasible to work with and ensure the end product would be as durable as possible.

Up until this stage in the process, the vast majority of the work had been done just using my hands. However, when it came to creating an interesting base texture on the sculpt, I needed more precise tools. Much of the texture was created using a rounded brush with wire bristles.

With the sculpt finished and dry, I progressed onto encasing it within a mould. To make the pieces of the mould, I applied wet plaster bandages to the sculpt. When the mould had set, the pieces were removed from the clay. The mould now had all the detail of the clay sculpt imprinted into it. Once the mould was ready, I poured liquid latex into it to set. When the latex was set, I retrieved what would be the mask from inside.

Due to the natural wear and tear the mask would experience on stage, I knew the paintjob would need to be as durable as possible. I used Supersaturated paint for the base coat. Supersaturated paint is durable and flexible when dry. This would be useful for a mask that changes hands – and heads – several times a show.

I first applied a grey base coat. On top of this, I added even more texture using a mixture of fake gravel intended for architecture models and PVA glue. This made the surface of the mask appear more crumbled. I then painted on washes of black, dark greens and dark browns. The black in particular seeped into the ridges, cracks and textures on the mask and gave it a greater depth and were evocative of a ruined urban landscape.

When I saw the actor wearing Cthulhu on stage for the first time, I was particularly struck by the contrast between the grim, surreal mask, and the bright white of her eyes piercing through it. The relationship between the mask and the performer brought the final element of life to the monstrous creature that haunted the stage.

Pomona is at the National’s Temporary Theate until 10th October 2015. For more information on Isa Shaw-Abulafia’s work, visit her website.

Stewart Pringle’s review of Pomona