How to build a plaster person

Plaster is a very cheap and easy medium to sculpt with. Traditionally it has been used for casting, and occasionally for carving, but it’s getting a reputation as a modelling material too. It has a short setting time so you to work to a kind of rhythm, with an enforced thinking time. Having said that, you can buy chemicals that slow the setting process down for a less frenetic experience.

You can start small, make armatures of wire, or anything really, as long as it  can keep it’s shape and doesn’t collapse when it’s moist. It’s good to use materials that aren’t too smooth, so that the plaster has something to adhere to. I’ll talk a bit later about how to mix plaster and work with it, but for now I’m going to talk about life-size stuff.

Once you’ve got your model (assuming you’re using a model) the first thing to do is to document them. You’ll need to take photos from all around the figure, making sure the focus is at it’s least distorting, and thinking consciously about the angle that you’re taking the photo from. It can be very useful to have an image from directly above, if you can get hold of a ladder. If you’re using a professional model they may not agree to photos being taken, so discuss it first. You’ll also need to measure them using a tape measure, and if you want to be professional about it, calipers. Here is the planning sketch for the man on the tube train, including the seat.

There is no end of measuring you can do, and this is one of those occasions where more is more. But you’re measuring for the skeleton inside at this stage, so there’s a bit of wiggle room. Think about the angle of the back, and where the weight is. Try and imagine the skeleton inside.

Once you’re happy with your measurements you can build an armature, which is the skeleton. I have made armatures of wood, but they’re harder to angle properly, and absorb moisture which can make the wood distort and the plaster crack. Unless you’re going to waterproof the wood, and are a confident woodworker I wouldn’t recommend it. There is a very friendly welding workshop beneath Cambridge Heath station, canofgas, who let me weld and provide assistance. In Walthamstow Blackhorse Workshop is also excellent, happy to help with all sorts of projects. I can’t recommend them highly enough. If you can’t find a welding workshop near you there are some relatively cheap stick welders, but you’ll have to get the gloves, clamps, grinder, helmet etc and also an appropriate electric connection, and probably someone who knows what they’re doing… You can cobble together an armature out of anything really though, you’ll just have to be imaginative and thoughtful.

It’s worth considering at this stage how the piece is going to stand up. Does it need a base? Is it going to be sitting down? Will it need to attach to something?

The welded skeleton for most of the Waiting figures is very simple. There’s a rectangle for the back and two legs, angled at the knees. For some there’s also a neck (1). For the arms, the feet and the head I used 9.53mm aluminium wire, attached with hose-clips (2). It’s good to have rock-solid base, but it’s also good to be able to adjust the edges, especially the arms. Aluminium wire is great for this because it’s stable when it’s in place, but bendy enough to change the pose if you need to. Polystyrene is wrapped to the skeleton with wire (3). It’s surprisingly difficult to find polystyrene. Most big chain shops leave it at the warehouse. DIY superstores are a good source, and fishmongers. I found a big hoard at a house that was being gutted, and they gave it all to me. It’s great stuff, extremely stable, keeps its shape and very very light. It’s easy to cut with a saw too.

Wrap the form in chicken-wire, making sure that the edges point in – there’s nothing worse than smoothing on your first layer of plaster and getting a deep scratch down your palm (4). It’s at this stage that the thing starts to look a little human and you can work out what’s working and what’s not. Even through chicken wire you can stab into polystyrene with a screwdriver and pare it back. Messy but effective.

Fine casting plaster is about £13 for a 25kg bag and it goes a long way. You can afford to make mistakes. You’ll need four buckets, two filled with water. The first bucket is to wash in, the second is to pour the water and the other two are for mixing plaster. For the first layer you’ll also need wide-weave hessian called scrim, which comes in a roll and can be cut to smaller lengths. You’ll also need to wear a mask over your nose and mouth, at least while you’re mixing the plaster. You really don’t want to get plaster dust in your lungs. Fill the mixing bucket with water, only about 5cm deep. Take handfuls of plaster powder and pour it in until it stops absorbing into the water and forms a dry powdery layer all across the surface of the water. Then wait until the water is absorbed, you’ll see it change colour. You can mix it with your hands now, until all the lumps are gone. It should be about the consistency of thick custard. If it feels too watery, leave it to set for a few minutes and test it with your fingers. Put in a length of scrim as evenly as you can then lift it out, trying to keep as much plaster on as possible, and lay it on your sculpture (5). If you put some on the top first you will have gravity on your side, and it will be easier to attach more underneath afterwards. Carry on until the whole thing’s covered.

When you’ve used up the plaster, rinse yourself and the bowl in the washing bucket. If the plaster is too hard, leave it and use the other mixing bucket. When you come back to it, push the sides in a bit, then turn it upside down over your rubbish pile and push the bottom. Most of the plaster will crack away. If there’s still some left scrape it away with something hard. NEVER wash wet plaster down the sink. I’m sure you can work out why. When you have finished with your plaster project, the washing bucket will have two layers, watery on top and plastery underneath. Pour off as much of the top layer as you can and leave the rest to settle. Repeat this until it’s just sludge then leave it to dry out. You can throw it away then.

After this you can add more layers of plaster without scrim (6). The plaster for this should be a bit thicker, either by adding more powder at the beginning or waiting ’til it’s set more before applying. As you work you’ll learn more about the different stages of setting, but a rule of thumb is, when you lift up the plaster and drop it back into the bucket, it shouldn’t sink back in completely.

As you go, you’ll find you need to use less plaster for the details like hands and faces. You can buy really lovely rubber bowls for mixing plaster, which are very easy to clean and take smaller amounts of plaster. Alternatively, use yogourt, margarine, water packaging. When I went on a student exchange to Prague about 23 years ago, they used plastic footballs cut in half. I’ve tried this since, but they don’t make footballs like they used to.

You may need to take plaster off as well as pile it on. You can use a hammer and chisel. Actually I often just use a wooden mallet after the first layer of plaster, and whack back bits that are too far out. Or you can use a file, or a surform. I find modelling tools are useful for details like noses and mouths, and occasionally rifflers if I need to file a small area.

That’s about it. Here’s a list of materials, with some idea of where to get them:

from DIY shops:

measuring tape, toolbox saw, needlenose pliers & snips, boltcutters (not absolutely necessary, but useful for cutting thick aluminium wire), hose clips, screwdriver, wooden mallet, chisel, files, scissors, mask, overalls, buckets, tarpaulins.

from specialist shops:

calipers, galvanised wire, thick aluminium wire, fine casting plaster (if you want something harder, get crystacal. It costs twice as much), scrim, rifflers, plaster bowls.

Tiranti specialises in sculpture equipment. Canonbury Arts are very friendly and informative about sculpting and especially casting materials.

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