chapter 6

model makers – the professionals

For professional animation, a model making company like the UK's Mackinnon & Saunders work from the animator's sketches and then make a 3D maquette, a blueprint from which they make moulds to make the models. Mackinnon & Saunders started working with Cosgrove Hall Films in Manchester in the 1970s. At Cosgrove Hall, they learned their trade as the company developed and grew. Many techniques we all use today were developed at Cosgrove Hall and many world-class animators such as Paul Berry, Loyd Price, Sue Pugh and Barry Purves learned the ropes there.

Mackinnon & Saunders specialize in models for series work and features, making puppets that are robust and easy to repair with standardized parts to keep them exactly the same all the way through the shoot.

Ian Mackinnon describes the process:

A lot of the animators we've worked with over the years have done their own model making as well. People like Jeff Newitt and Ken Lidster from Loosemoose. They would probably make their own puppets if they had time to do it. They like to give us some sort of reference to work from, whether it's a sculpt or a sketch. It's the job of the sculptors then to interpret it and take it from a sketch into 3D form.

Whilst the sculptors are working on blocking the character out they've got to be conscious of what the job entails from a stylistic point of view. If it's Jeff Newitt's – there's a certain way that he would sculpt a character, similarly with Ken, so we try and mimic that. They would put their stamp on a sculpt even though they're not doing it themselves. The sculptors have to mimic the style so that hopefully, when the costumes and the sets all come together they all look like one complete world.

There might be 6 or 7 different people working on a character at any one stage – its got to go through the mould makers and the armature makers – so to have one (blueprint) model, whether it's painted or whether its blocked out, is useful for everyone to go back to and make sure all the jigsaw puzzle fits together at the end. Also to make sure we've not lost something along the way: the proportions haven't altered because someone's taken a wrong measurement.

the maquette

Figure 6.1 Sculptor working on a maquette. Courtesy Mackinnon & Saunders. Photo © Susannah Shaw

With several characters in a story, the model makers will block out all of the characters as maquettes, spending about a day on each one to get the basic proportions. Complications of scale and proportion arise when there are a mix of human, animal and bird characters. These problems can all be ironed out in consultation with the animation director at the maquette stage.

At this stage the sculpt is made over a basic brass sleeve and wire armature, so it can be disassembled, which also helps when you're sculpting it. Little details on the hands and work on the head can be done separately, away from the body; this also makes it easier to finish off. The final materials should be decided on during the sculpting stage. It'll depend very much if the character's got to do lip sync – you might want substitute or replacement mouths. If so, you would choose a hard head. If it's going to be a mechanical mouth, (Mackinnon & Saunders specialize in mechanical movement inside the head) then it would need to be silicone or foam. Using a mechanical head is a costly process.

All the separated elements then go to the mould making department. The whole process of building up the puppets is dealt with in different departments: sculpting, mould making, casting, painting and armature-making. Once the sculpt is approved, the armature is machined and assembled.

ball and socket armature

A ball and socket armature is more durable and reusable, altogether tougher than a wire armature, and is necessary when a puppet is being made for series or feature work. Apart from its strength, it gives the animator a greater degree of control for finer, smoother movements.

English armatures tend to be made with steel rod and plate construction with ball and socket joints. Joints are made with one or two steel or phosphor bronze ball bearings sandwiched between balanced steel plates. US armature makers use steel rods and ball bearings made with chromed mild steel. The steel balls are annealed (heat treated) to strengthen them. Blair Clark, now a visual effects supervisor at Tippett Studios, was a model maker on Tim Burton's Nightmare Before Christmas and recalls ‘the animators required joints that could take a great amount of wear and tear. Light scoring on the balls, caused by tightening of the joints, could easily render the armatures unusable. So to prevent constant breakage of the armatures, we made them very strong. I remember the English animators who came over, Loyd Price and Paul Berry, were surprised at how hard they were!’

Figure 6.2 Working on a mill. Courtesy John Wright Modelmaking

making your own ball and socket armature

If you are considering making your own ball and socket armatures from scratch, it can be a bit complex, but possible. The cost of the quality of equipment you need to make ball and socket armatures could become prohibitive. Rather than considering buying your own lathe, it may be wise to approach a local art college. A jewellery making department, or even a sculpture department will have all the equipment you need and may relish a challenge.

However, it is much easier to make one up from a kit. You can order all the pieces you need from some model making companies (see appendix 1 for addresses). They can usually supply you with the information you need if you are going to build your own.

Tools that you will need to make up your armature include: a hand blowtorch, pliers and Allen keys. Cheese head, flat head and grub screws are useful. Use silver solder, as soft solder won't solder stainless steel. Don't try using glue for holding your armature together – it will fall apart under any pressure! Health and safety warning: Take great care using a blowtorch. Use a mask when using silver solder as it releases harmful fumes.

Good communication is essential when ordering a ready-made armature – so get your dimensions right and use graph paper to draw a plan of your armature (Figure 6.3). It's useful to show the dimensions of the covering material as well. You may know what size and type of joints you want, if you don't it's useful to indicate on the drawing where and how your character will need to bend. It may be useful to fix a lightweight block of balsa or insulation board on the chest or hip plates, below the covering surface as something for the animator to get hold of, a grabbing point.

Figure 6.3 Scale drawing for armature. Courtesy John Parsons

Depending on how many limbs your character has, whether it's humanoid, quadruped, or even alien, you should be aware of the way it moves; this will then determine what kind of joints and what size of joints it will have. For instance, the hip joints can have a lot of wear, so you would be better spreading the tension over a double joint at the top of the leg, but you should use a single joint at the elbow to avoid it bending back on itself. Single joints allow for single axis movement, and double joints or full rotation, but beware of double joints folding over onto each other.

humanoid joints

neck:	double joint to allow for full rotation
shoulders:	2 x double joints
elbows:	single joint, for single plane of movement
waist:	double joint
hips:	double joint
knees:	single joint
ankle:	single joint
foot:	hinged plate (a single flat plate foot makes walking very difficult)

rigging points

Your character might need to fly or leap through the air in which case it will need a safe point to attach it to a rig. You may want to incorporate a K&S rigging point either on the hips or chest of the puppet. This would slot into a corresponding brass tube on the rig. Or you might want to attach the puppet to wire, in which case you can attach tungsten wire, which is fine and very strong, and almost invisible. Or fine fishing line – this can catch the light a little more – but it can be dulled with wax, blackened with felt tip, or even coloured to match its background. To keep the puppet steady you will want two or more rigging points – the neck and the waist. For professional filming, the safest method is to use a rigging stand, with ball and socket joints; these can be painted out in post production. The reason I mention this is for professional filming is that painting-out a rig in post production is very time-consuming and therefore expensive, and should be avoided as far as possible. Learning to animate with the idea that you can change everything in ‘post’ is not going to be a very instructive process.

Don't over-tighten joints – never use excessive force manipulating the joints on your puppet, you can easily buckle the plates or rods. Once they are buckled they are very difficult to repair. If you feel that a joint is becoming too loose or too rigid it may be that the Allen key is worn, or that the bolt heads inside are worn which can be worse, as they then become impossible to remove. Use Allen keys of the necessary sizes to make fine adjustments to the joints when necessary. It is useful to keep a drawing showing the joints and which keys are used for which joints, either to save time, or if you have someone else animating your puppets.

Figure 6.4 (a) Mechanical man armature. © John Wright Modelmaking

Figure 6.4 (b) Computer aided design (CAD) armature. © John Wright Modelmaking

Figure 6.5 Ball and socket pieces. Courtesy John Wright Modelmaking

Figure 6.6 Professional rig arm. Courtesy John Wright Modelmaking

mould making – hard and soft moulds

the sculpt

If the puppet is to have a foam latex, or silicone covered body, you will need to first sculpt your model to make a mould to cast these materials in. This is called the sculpt or the maquette. You may also need to make some hard parts for your model: sometimes feet, or hair, or even faces may need to be hard. The general rule is: If you are casting a hard piece, you will need a soft mould (silicone) and if you're making a soft piece, you'll need a hard mould (plaster, resin or fibreglass).

Make your armature. You may want to make separate parts of the body that can join together. In this case it's useful on the armature to glue (epoxy) brass sleeve tubing at these points (arms to hands, neck to head).

It's best to use a very firm clay for your maquette, as details and fine lines have to hold as it goes through the foaming or moulding process. Blair Clark, visual effects supervisor at Tippett Studio prefers a Chavant clay. Mackinnon & Saunders in the UK use Harbutts, now made by Newclay Products. Others use Plastiline. Build up the clay and sculpt to the right shape.

Figure 6.7 Rocky maquette made by Mackinnon & Saunders. Courtesy Loose Moose Productions. © Brisk Tea/JWT

Sculptor Stuart Sutcliffe, working at Mackinnon & Saunders, sets a mirror on the other side of the character he is sculpting, so that he can check the figure for symmetry. ‘When you look at things, you tend not to see any discrepancies, your eye gets used to it. But with a mirror, the image is reversed, it confuses your brain and you can suddenly see all the discrepancies: there's a big lump on that side, or there's a sharper curve there than the other side.’

Figure 6.8 Stuart Sutcliffe at work. Courtesy Mackinnon & Saunders. Photo © Susannah Shaw

textures

For textures such as wrinkly skin, dinosaur skin, or fabric you can use ready-bought stamps from various sources or make your own taking latex casts off any surface: old leather, almond stones, bark, leaves, stone. To make good facial wrinkles on Plasticine, cover it first with cling wrap, then mark with a sharp edged tool, it just softens the sharp edges.

undercuts

The presence of undercuts, i.e. a corner or curve that will be problematic when trying to release the mould, is probably one of the most important aspects of mould making. To assess how many pieces you will need for your mould you will need to look the model over very carefully to see if there is an undercut. Don't rush this stage. You will need to work out whether you will need more than two divisions for the mould, and where those divisions should come.

Figure 6.9 Texture stamps. Courtesy John Parsons. Photo © Susannah Shaw

Figure 6.10 The problems of undercut: (a) wrong, (b) correct. © Alec Tiranti Ltd

seams

You will also need to think carefully about where the joins come on your model. This is because when you first take your cast out of the mould, you will inevitably have excess foam or silicone around the join (flashlines) which will need to be cut or sanded away. It would be unfortunate to design your mould so that the seam comes over the face, or some other exposed area. The sides of the body are generally easier to clean up.

The different elements need to be worked out – the body might be cast in foam latex; the head and the hands might be cast in silicone, which means they'll need separate moulds. For maintenance purposes, if it's a series, hands need recasting on a regular basis. Because the wires in the fingers are heavily used, they should have a separate mould so you don't have to cast the whole body each time. The body should only need to be cast once – it should last for a whole series, especially if it's got a costume over it.

Figure 6.11 (a) Body mould; (b) Glove mould. Courtesy ScaryCat Studio

making a hard mould

Making a plaster or resin (hard) mould for foam latex or silicone:

1.Make a bed of potter's clay or any clay of a different base to your sculpt – potter's clay is water-based and soft enough to bed an oil-based clay (Plastiline, Chavant) sculpt in without spoiling the detail.

2.Build up walls around the bed to the height you need, with card, foamcore or Lego. Lego is versatile, re-usable and can easily be found at car-boot or yard sales. You can build up the walls to whatever height you need.

3.Bed the sculpt into the clay, making sure the clay comes up to your division marks. Ensure that the clay fits exactly around at your mark; it must seal all the way round the model. Cling wrap can be placed underneath the majority of the sculpt before it is embedded in clay. This is to make the clean-up process easier when preparing to make the other parts of the mould. Any creases can be easily touched up on the sculpt.

4.At this stage you also need to make ‘key’ or location points that will ensure your mould halves fit exactly together. These can be made using small cones of clay, or make a dip with a marble at several points in the clay around your sculpt (make sure you don't sink the marble any further than the half-way mark, or you'll have an undercut problem!).

5.You will also need to put in channels to allow the excess foam latex or silicone to escape when you press the mould together.

plaster moulds

Plaster is cheap, non-toxic and quick. It can crumble if handled a lot. Cristacal or Ultracal is recommended. Health and safety warning: Ultracal has lime in it – wear gloves when handling. Keep away from eyes.

To make a plaster mould, brush on your first layer of plaster, this'll ensure plaster has got into every corner. Coat the sculpt with layers of plaster, each coat being added when the previous has become warm. (Plaster warms up as part of the chemical process of hardening.) When cool again, it is set; turn over and take away the clay.

Coat the first half of your mould with a release agent – a petroleum jelly like Vaseline is the cheapest and most effective. Then repeat the plastering process over the other half of your sculpt.

If there are more than two parts to the mould (this can depend on the shape of your model), you will need to repeat the process for each part.

resin moulds

Fast cast resin – more expensive, this is a polyurethane-based resin therefore quite toxic, but useful for series work and features as it is very strong.

Fibreglass resin (or GRP, glass reinforced plastic) – uses a catalyst (and an accelerator if required) and is built up in layers with a fibreglass matting. Useful for series work, very durable, but toxic.

Epoxy resin mould – brush on the first layer, and then pour on the remaining resin. Make sure your box is tight, as you won't want resin leaking over your furniture. The resin can be mixed with metal powders such as aluminium for strength, e.g. a two-part 50:50 mix sets in about 5 minutes (depending on type purchased). Consult with the manufacturer.

With these polyurethane-based resins there are certain safety measures you should protect yourself with. Wear a mask to avoid inhaling fumes. Use a barrier cream on your hands as prolonged use can cause dermatitis. Wear goggles if there is any chance of the resin making contact with your eyes. All the containers should have instructions on them.

making a soft mould

silicone moulds

Silicone is very versatile. As it is so tear-resistant you don't need to worry about undercuts, you can pour the silicone into a containing box, and, once set, release the cast from the mould with one cut and manoeuvre your cast out. Silicone requires a catalyst. It can also be used for Plasticine as a press mould.

plasticine press moulds

Making repeat models in Plasticine can be useful; the Plasticine is built up layer by layer in the mould. Rex the Runt was made with silicone moulds. The silicone is tough and quick to release, making it useful for series work. Fastcast resin or plaster could also be used to make a press mould. For hard press moulds you would need a reliable release agent. Soapy water, washing up liquid or petroleum gel can be painted into the empty mould as a release agent to help remove the Plasticine after it has been pressed into the mould.

There are seven basic rules for mould making:

For a hard cast, use a soft mould; for a soft cast, use a hard mould.

Plan your undercuts.

Think ahead with seams/flashlines.

Remember to add location/keys to your mould pieces.

Remember your release agent.

Remember to block vents – after casting.

Don't rush!

casting

casting foam latex

Remember to first brush your mould with a release agent (Figure 6.12b).

The basic process for mixing foam latex is:

foaming up to desired volume at high speed

de-ammoniation at mid-speed

refining cell size at low speed

gelling agent addition.

You will need good ventilation when mixing latex as it gives off ammonia fumes. Depending on temperature, humidity, mixer type and size of the run, this process can take anywhere from 15 to 30 minutes. (Runs smaller than 150 g of latex are not recommended.)

The following two sets of instructions are meant only as a guide and are for 150 g of latex using either the Kenwood Chef mixer widely used in the UK (which has a choice of speeds), or the Sunbeam Mixmaster used in the USA, (using the small bowl). The Sunbeam produces a foam of superfine mixture. It has a highly efficient beating action, driving off ammonia very quickly. However, the mixer is less efficient when used in a large bowl.

Figure 6.12 (a)–(q) Sequence of photos mixing and casting with latex. Courtesy of John Parsons. Photos © Susannah Shaw

1.Shake all components well and into the mixing bowl, accurately weigh out:

	150 g latex
	20–30g foaming agent
	20–30 g curing agent.

2.Foaming – foam at high speed for 3–5 minutes or until the desired volume is reached.

3.De-ammoniation – reduce to medium mix speed for 3–5 mins.

4.Refining – reduce to lowest speed for 5–6 minutes.

5.Gelling agent – at the end of the mixing time add 5–10 ml of gelling agent to the foam. Mix thoroughly for 60–90 secs (the addition of a latex colour at this stage will give an indication as to when the gelling agent is fully mixed in). (The longer times given are recommended as a starting point for 300 g of latex.)

6.Put your armature in place in your mould. The PTFE tape on your armature stops any of the brass from the armature discolouring the latex. Then fill the mould by hand, brushing the latex in to ensure coverage (see Figures 6.12(g)–(j)).

7.Press together two halves and weigh them down or clamp them. Then inject the foam down one of the channels. The injection hole should direct the foam to the core. Let the foam work itself around the whole mould. When you know the latex is coming out of every vent, plug the escape vents with wet clay or English Plasticine (American clay will melt in the oven).

gelling times

The gelling or setting time of the foam at a room temperature of 20°C (68°F) is between 10 and 20 minutes. Longer gelling times may occur and produce perfectly acceptable foams. Faster gelling times can be achieved by slightly increasing the amount of gelling agent, increasing de-ammoniation time. The foam must be set before placing in a hot oven, otherwise foam breakdown could occur. An easy way to test this is to pour left-over foam into a paper cup to a height equivalent to the thickest piece of foam you are casting. Once that has gelled, the foam in the mould should have gelled as well.

curing

When the foam has set (i.e. become a semi-solid easily de-formed material throughout) it may be cured in a suitable oven for 2–3 hours at a temperature of 90–95°C. Curing times may vary depending on the thickness of plaster moulds, etc. You may have to shorten times for fibreglass or epoxy moulds, and increase curing times for thicker moulds or silicone moulds with plaster positives. After curing and allowing sufficient time for the moulds to cool down, remove the foam from the mould and wash. Cured foam is more readily removed from warm, rather than cold moulds (Figure 6.12(l) and (m)).

Plaster absorbs the moisture, generally allowing air to escape, but if you find an air bubble is trapped, more likely if using a resin or a fibreglass mould, you can drill holes in the mould to allow air to escape from likely trapping places. It can take two or three bakes to get a successful cast.

Wash and trim the latex carefully with nail scissors or a scalpel (Figure 6.12(n) and (o)).

care of latex

Latex wears well but will tear under strain. Human sweat will help to rot the latex, so keep hands as clean as possible, using wet wipes. Latex can be repaired with a contact adhesive, coat both surfaces, allow to dry and then press together.

Spirit-based cleaners will dissolve latex during the mixing and airing stages, although once baked, latex is more resistant. As with Plasticine, keep it from becoming tacky with a little talcum powder. Latex doesn't have a very long shelf life; up to six months if stored in ideal conditions. It would make sense to leave buying it until you are absolutely ready for it.

casting silicone

Casting silicone does not involve baking. The main consideration when using it for your puppet is that it is quite resistant (springy) and may reduce the control you have over its movements. One good solution is to cover your armature with ordinary foam – upholstery foam – so that you are only covering a final layer with silicone. That way you will get a reasonable response from your limbs, as well as an easily cleaned puppet.

Once you've mixed your silicone (as per manufacturer's instructions), it is injected into your mould (a large syringe can be bought at a plumber's shop) until it is coming out of the vents. Remember to block any vents with wet clay or English Plasticine, as otherwise the silicone will continue to dribble out.

Leave to cure. Curing times for silicone depend on the type of silicone and how much catalyst is added. On the whole silicone will take about 10–12 hours before it can be removed from the mould.

When set, remove from the mould and clean with isopropyl alcohol. You can sand the seams with fine sandpaper, or remove them using a fine buffing tool with a Dremel or multi tool.

colouring

For latex there are liquid latex paints that can be painted or sprayed on. Before spraying, you will want to ‘key’ the cast first with liquid latex. The inks can be sponged on and thinned with white spirit. This will cause the latex to wrinkle, but it will settle again.

Water-based acrylic paint like Liquitex can give your foam latex a ‘plasticiney’ look and has a good opacity and a glossy finish. Acrylics can be mixed with Copydex, or similar latex-based adhesive, to bond well with the latex. For a similar look you can use a water-based gouache.

For resin or silicone pigments, check with the manufacturers for compatible dyes (Figure 6.12(p) and (q)).

costumes/dressing

Many puppets have their clothing sculpted and moulded in foam latex or silicone as part of the whole, but making fabric costumes for your puppets gives them a rich sense of individuality. The most important consideration is the scale of the fabric. You will want to look for prints and textures that suit the scale. If you want a specific pattern, you may print your own fabric.

Nigel Cornford has made costumes for puppets from the early days at Cosgrove Hall: ‘If a fabric is too light it is liable to ‘‘crawl’’. In other words, you're aware of the constant movement caused by the animator touching the fabric while filming. In King Kong and the early Harryhausen movies, you can see the fur ‘‘crawling’’. So the material has to be stable. I start with a basic white cotton which I dye or screen print and sometimes embroider. That way you can get the scale right. I prefer not to stiffen the fabric, but if it's necessary, if a cloak has to flap in the wind, I'll wire the hem or sometimes I'll stick it to Rosco foil. I prefer to hand stitch costumes for puppets, machining is not versatile enough. I would say, choose the fabric you want, and work your way around it.’

If you're using leather you would want a contact adhesive. If you want a close fit, use fabric cut on the bias, that is cut diagonal to the weave of the material; you will find it gives more flexibility as you stretch it around the puppet. Remember to leave access points for any refurbishment of the puppet. It is possible to glue the fabric to a very thin layer of foam to give it manoeuvrability.

Figure 6.13 Puppet from Rigoletto. Wardrobe: Nigel Cornford. © Barry Purves/S4C/BBC

For decorating your fabric, pens and fabric dyes are available from craft supply shops. If you are making an additional puppet on a bigger scale, for close-ups, you will need to take the texture and pattern of your fabric into account.

During the model making process it is worth documenting and photographing each stage – there is so much useful information you discover as you experiment, and it is useful to have a reference to processes used. Model making is an under-documented area combining an extraordinary range of skills and as such is always in demand for film and theatre and even medical reconstruction and prosthetics.

glossary of model making materials

For list of manufacturers and outlets see appendix 2.

Allen keys: hexagonal keys available in various sizes, metric and imperial, used for tensioning armatures.

aluminium wire (armature): comes in various thicknesses ranging from 0.5 mm to 10 mm in diameter.

baking oven: must have a low temperature of 50°C showing on the dial.

ball and socket armature: you can order joints, rods and plates from specialist companies.

Chavant clays: a variety of sculpting clay.

contact adhesives: various makes available, e.g. Evostick, useful for sticking many materials.

epoxy glues: very strong glue, a standard 5 minute epoxy is available from hardware and model shops.

insulation board: dense foam that can be carved (available at DIY stores).

Fimo: modelling clay, good range of colours, bakes hard. Used for making props (available at model shops).

foam injector: a large syringe that can be bought at plumbing shops. An icing gun can be used as a substitute.

foam latex: a ‘hot’ foam, it needs to be baked in the mould. Can be mixed to different densities for different purposes. If mixed fast, it will provide an airier, light foam (used in prosthetics). A slow mix will provide a denser, heavier foam that is good for models and puppets.

food mixer: (Kenwood Chef/Sunbeam Mixmaster) for mixing latex.

glass fibre: used with resin to make very strong moulds. Tendency to warp, so nuts and bolts are recommended to keep parts together when moulding and storing.

Lewis Newplast: Plasticine or English clay has a good colour range (19 colours), colours more subdued than the US Van Aken, and does not melt. Available from model shops and art suppliers in the UK.

Lewis Uro: like Sculpey, similar use (available at model shops).

Milliput: an epoxy putty, also used for making props, white or pink (available at model shops).

Plastiline: comes in two colours: grey or buff. A hard modelling clay, ideal for maquettes for hard or soft moulds. Can be melted or can be made really hard if kept in a fridge.

rare earth magnets: otherwise known as neodymium iron boron magnets. Very powerful and quite expensive magnets to fix your puppets’ feet to the floor when using a perforated steel base. From £6.00.

release agents: Vaseline is cheapest and best, must be used judiciously to avoid clogging in corners. Available as sprays and aerosols.

resin: a cold cast product used for making hard parts: hands, feet, and hairpieces. Also used for mould making for silicone or foam casts. Can come with metal powder, i.e. Formite, aluminium powder in resin.

Sculpey: a polymer clay. Available in several types: Original Sculpey, Super Sculpey, Sculpey III, and Premo Sculpey. Must be cooked and cured. Good range of colours (available at model shops).

sculpting tools: used for smoothing, texturing, gouging, shaping clays. People build up a range of tools to their own liking. (Available at model shops and pottery suppliers.)

silicone: makes a rubbery smooth-textured material. It can be cast cold, with no baking required; the colour is fast and can be mixed to match a Pantone reference. It provides a resistant and springy material. Ideal for replacements (substitutes). Very strong, tear-resistant and easy to clean. Good for moulds for resins and Plasticine press.

sticky wax: a removable adhesive material useful for fixing props in place (available at model shops).

Van Aken (Plastalina): fudgy texture, it can get sticky and soft under lights. Has a melting point, which is good for moulding. Colours are saturated but not fast. Good for doing food and when melted, makes a good gloss. Sold in the US.

wood: for bases, blocks, and balsa wood for cores, props, etc.