‘White card models’ for film/tv work

The following aims to serve as an introduction to the purposes of the so-called ‘white card model’ in film/tv design work, what it should include, and the materials one can choose to make it. In the case of the materials and techniques recommended, it is really just an overview of possibilities and doesn’t go into full, step-by-step instruction on how to build. It is important to make the distinction right now between the ‘white card model’ meant in this case and the other case .. the exploratory, often rough and inexact, sometimes coloured, ‘sketch’ model which is often referred to by the same name, especially in the theatre. The ‘white card model’ of the present context is, in many ways, anything but rough and inexact and most often, due to its usual place in the chronology of design steps, it is no longer exploratory.

‘White card models’ explained

Although the film/tv production designer is free to use a wide variety of visual means in developing and recording a set design concept, including rough or ‘sketch’ models during the early stages, the so-called ‘white card model’ produced for the final stages conforms to very specific requirements. It is usually made once the design has been finalised, most often incorporating the detailed technical drawings created for the construction of the set. It is therefore quite literally a three-dimensional ‘blueprint’ of the intended design.

It is usually not a realistic, atmospheric rendition of what the set will look like, let alone how it will appear in the film. It may offer no information on colour, little on texture and materials, but all the most essential information on space, structure, movable elements and their practical implications. The designer may build a version earlier in the design process to test the design’s three-dimensionality ( to check general proportions, to better visualise filming possibilities etc.) but these things have usually all been worked out by the final stage and here the model made is more of a communicative device than a ‘testing’ tool. It serves as a communication to the whole film crew. It tells the director and the cinematographer exactly how much space there is for whatever action is required for a scene but also gives a summary idea of what will be seen behind it (this supports the value of creating technical drawings/model with some graphic indication of surface textures etc.). In addition it tells the cinematographer, and camera, sound or lighting crews, how much space there will be for equipment and whether any obstacles such as pillars, steps or levels need to be planned for. It gives an overview for the technical crew responsible for building and furnishing a set (or modifying an existing one) of how much work is required. It furnishes the financial administrators with the same overview to help them assess the costs.

The most common scale for this model is 1:50 (or the equivalent 1:48 if Imperial ..feet and inches.. is used). This is usually the scale in which the main technical groundplans are drafted, and it is generally accepted that this is neither too small to show a significant amount of graphic detail nor to appreciate proportion in relation to the human figure. In any case models in a larger scale i.e.1:25 simply become too big to be manageable. Common types of card can be used, with the drawings spraymounted to them. These are then cut out and assembled to form 3D structures. The ‘rule’ is that anything which has a significant physical bearing on the set space (such as a pillar, steps, changes in floor level, opening doors, railings etc.) needs to be represented in 3D whereas anything which can be ignored from the point of view of space (such as shallow decoration or panelling, light curtains etc.) can be left flat as drawing. I always recommend that, at 1:50 scale at least, one can safely represent most things under 5cm deep (in reality) as flat drawing. 5cm amounts to a thickness of 1mm in a 1:50 scale model. On the other hand, anything protruding 5cm or more should be given that physical thickness in the model! For example a thin modern radiator could be just drawn whereas an older, more ‘bulky’ type really needs to be represented more physically in 3D (at the very least as a separate cutout which is stuck at the correct distance from the wall to convey the object’s total depth). Another common example is bookshelves, which also really do need to be shown in their proper depth however ‘fiddly’ this might seem. This is to ensure that there can be no misunderstandings about the exact spatial limitations of the set, which is of vital importance considering the amount of money in filming-time which such misunderstandings might cost.

One exception to the ‘5cm rule’ may be the floor area .. and this calls for the personal judgement of the designer/maker. In the case of the floor, even differences under 5cm could have a huge physical impact in terms of moving things around, so it would make sense to emphasize these physically in the model. It helps even more if the height indications included on the drawn ground-plan are kept visible .. another good reason for using the actual ground-plan, pasted to the baseboard.

There is always a margin left for personal judgement! Just as there is always room for the personal touch, to be a little bit more personal, creative or even .. aesthetic! .. in how one renders one’s own technical drawings (better still if it actually enhances rather than detracts from the communicative clarity of them!) the same should apply to the white card model. Showmanship may not be strictly necessary in practical terms .. but it can inspire!  Even this kind of model can be stylish as well as functional and, dependant on individual taste, ability and.. most importantly.. time, it can be embellished with graphic detail, structural finesse or effects designed to ‘sell’ the visual concept. Even at the later stages of design development it pays to be truly creative with the model, to be inventive with methods of representation or ‘simulation’. Such experimentation can directly pool into what I call our general ‘creative matrix’ as designers. I wouldn’t say that elements of colour are totally ‘banned’, but particularly here it is important not to upset the overall balance. Colour can become a distraction, giving visual weight to some elements to the detriment of a balanced overall view.

Above is part of a white card model made by Edwina Camm for ‘An Instance of the Fingerpost’ an MA Production Design film project at Kingston. Edwina drew her original technical drawings this way .. little needed to be added to create this rich, convincing effect when used for the white card model.

There is another form of ‘white card model’ often used in film which I’d call ‘virtual’ or imaginary .. where a building, structure or even a whole landscape is constructed in precise dimensions even though it will never be physically built in its entirety. These are just as important to the production process because they make sense of how the various embodiments of the ‘set’ (whether CGI, built interiors, realistic physical models made for filming) are meant to fit together. I will be coming back to these later, but for the moment we are still concentrating on white card models for physically built sets.

There now follows a short list of the most significant individual points worth noting:

The base on which the model is mounted should be flat and stable i.e. secure enough to be a good support, not only when transporting the model but also for resting it down even where there are no totally free table-tops available. Production offices are often like this, and certainly studios or locations with sets in progress. Mountboard on its own is never enough! Generally 5mm foamboard will suffice for an A2 size model and 10mm foamboard for A1 and is often a better option than choosing heavier plywood or MDF! However if the foamboard is warped (and the cheaper polystyrene core foamboards often are) this must be first corrected by firm bracing on the underside. Another important extra precaution is protecting the baseboard corners against knocks (perhaps just by gluing triangles of mountboard on the top side). There’s nothing that transmits an impression of carelessness more than a lot of bashed corners! These may well become inevitable with a ‘working’, much-carried cardboard model, but just a little bit of extra strengthening can limit the damage. One needs a balanced attitude with respect to all this .. on the one hand caring about one’s professional appearance but on the other accepting that in a heavily populated working environment one can’t remain too ‘precious’!

Model in preparation for the build of the Sarang moon-station for the film ‘Moon’ 2009 on Shepperton Studios K-Stage. Often to save time, and if changes are anticipated, the white card model is mainly held together with pins .. unfortunately these models are always falling apart! Photo courtesy of Gavin Rothery.

The ground level (at least the visible set floor) should also be represented in white rather than bare wood if this is used. There should be a unity .. or rather, the word is homogeneity .. of colour and treatment throughout the model. But it should show very clearly where the floor is ‘the set’ and where it is not, so sometimes it makes sense for the ‘offstage’ to be differently coloured. Most often the master groundplan is used, spraymounted to the baseboard. If this groundplan is properly done, then (sometimes overlooked) elements such as scenery seen through windows will be automatically accounted for in the model. For obvious reasons even small ground surface elements or slight level changes will have an impact on how the space can be used, so these need to be physically represented in the model rather than just drawn. If you’re lucky, slight changes in level are easy to achieve just by layering different thicknesses of card on top of the baseboard. If you’re unlucky and part of the floor sinks below the common ‘0’ level, this is another good reason for using something like 10mm Kapa-line foamboard as a base. The section that sinks can be carefully cut out (a precision job with the scalpel), the paper can be peeled from the back of it and the foam sanded to make it thinner, and the section can then be glued back where it came from .. now a little sunk.

There should always be at least one scale figure included, simply as a familiar indication of scale. In my experience, as long as the essential proportions are right this figure should be as simply conveyed as possible and flat cut-out figures often look better in this context than 3D ones.

Practicals (i.e. working or moving elements) such as doors, shutters or removable parts need to work in the model, or at least be clearly indicated as movable. This should remain within reason ..for example, it is easy enough to half-way cut through card to make a working door but it would be unreasonable to expect a working roller-blind! In cases like this the simpler shortcut would be to make the model with the blinds open and make separate inserts to convey the effect of them down if this is necessary. Even in the simpler case of practical doors it may be better just to glue them ajar to show that they’re practical. Having to flip little bits of cardboard open in the model just to show that they open seems a bit unnecessary and could even be dangerous to the model if nerves are affecting one’s motor-control! It is often necessary to make parts of the model removable so that, especially, interiors can be better seen and to take better photos of these parts. This may directly reflect how the set will be built for filming in which case the so-called ‘floating’ walls will be indicated on the groundplan. Ceilings are a bit of a ‘grey area’ (i.e. often misunderstood) when it comes to the white card model. Strictly speaking if the walls of a studio set are going to be built to a certain height, even if that extends beyond what the camera will see, they should be built to that height in the model. Similarly if a ceiling exists in a used location it should be included, to make it clear where it is, even if the camera is going to avoid it. This would then need to be made detachable. When the ceiling becomes a feature of the design it should definitely be included, but again detachable.

Windows which are meant to be seen through (or any transparent surfaces) need to allow just that in the model, and need to be cut out, and also surfaced on the back with thin acetate to make it clear if they are going to be glazed (this for example is something both the lighting and sound crews will need to consider).

It is a common mistake to forget that something will be seen through a window, or an open door. If the set design has been conceived and developed largely on the drawing board it may be only at the ‘white card model’ stage that this is even considered! By then it may be too late for major alterations or to create more space for backdrops etc. Digital insertion via blue or green screen, or even old-style back projection, may solve a number of problems .. but these also should be planned for earlier in the design process. This is yet another solid argument for starting the physical model process early on, if only as rough ‘sketch’ version.

Another example of the illustrative quality of white card models from Edwina Camm, also showing the importance of including the ceiling in this context.

If slender structures just as stair balusters or metal railings (although spatially flat) are left as blocked-in drawings they can create a false impression of space and often completely obscure the effect of the stairs. These are far better represented as cut-outs where humanly possible. An effective and often easier alternative however is to draw these structures with permanent ink on acetate sheet (but the acetate should ideally be matted to differentiate it from glazing).

There should be no short-cuts taken when representing steps, even long, regular flights of them (i.e. sometimes done by representing them as a flat card incline). This can be visually confusing. It is understandable because making them can be tedious, but ‘sandwiching’ foamboard or card to form the correct ‘riser’ (meaning the height of a step) and then simply layering these is one way of making construction much easier.

Should a ‘white card model’ stay white?

I’ve written elsewhere that I don’t consider pure white card to be the right medium at all when it comes to representing, or even just mocking up spaces. I think that at the very least off-white, beige or light-grey should be used because white is far too glaring .. it bounces the light within and around it like a pinball and consequently it gives a misleading impression of interior spaces! But it’s different when copies of the technical drawings are pasted to the surfaces .. there is less glare and, dependent on the style of drawing and the copier settings, often a variety of grey tones.

As I explained earlier, the effect should be monotone, rather than particularly white. The model can even be sprayed, as long as this doesn’t obscure the definition of the drawings.

SCALES AND SIZES

Since the white card model is commonly a pasted, 3D version of the technical drawings  one would assume that these dictate the scale of it .. but this is only partly true. As I’ve said 1:50 (or 1:48) is the most practical scale and the master ground-plans are often drawn in this scale. But the elevations (meaning the vertical faces of walls, structures etc.) may have to be drawn in a larger scale, such as 1:25, if there is a lot of detail. These drawings therefore have to be converted to 1:50 .. i.e. copied half-size.

Most people with some experience of working with scales would not have to think that long to arrive at ‘half-size’, or ‘50% reduction’ when thinking of the conversion from 1:25 to 1:50 .. it seems obvious. However, what if the elevations have been drawn in 1:20 scale and need to become 1:50? Less obvious, isn’t it? To solve this little mental problem we have to go back to ‘1:25 to 1:50’ and look at what we might have done. If we divide 25 into 50 we get ‘2’ .. if we then divide 2 into 100 we get ’50’. That’s the percentage reduction. So .. 20 into 50 gives us ‘2.5’ and 2.5 into 100 gives us ’40’ .. so this time it’s 40% reduction.

A common mix-up that arises when thinking or talking about models is between ‘scale’ and ‘size’. For example, a 1:50 scale model will be ‘smaller’ both in scale and physical size than the same structure modelled at 1:25 scale but the 1:50 version might sometimes be referred to as a ‘larger’ model because it enables a ‘larger’ area of the real thing to be modelled. To avoid the confusion one should make a habit of referring to ‘smaller’ or ‘larger’ only in terms of scale, i.e. a ‘larger’ model is one that is made to a larger scale even if it ends up a physically smaller portion of the whole. The scale 1:20 is a ‘larger’ scale than 1:25 but many people also get confused because, from the way it is written, it appears a smaller value. It may be a little easier when working with Imperial (feet and inches) and referring to ‘half- inch’ or ‘quarter-inch’ scales, more obviously decreasing in size.

By the way, another misunderstanding often arises when confusing dimension and surface area. For example, when asked to double the size of an A4 drawing many might think ‘A4 to A3’ but this, although doubling the surface area, is not doubling the dimensions. To double the dimensions you need to choose the next size up, i.e. A4 to A2.

Even if one has recently completed the technical drawings, before starting a 1:50 or a quarter-inch white card model .. or any scaled model .. one should take a moment to re-acquaint oneself properly with the scale again. One should, for example, look at how small a figure is (average male actor 1.75m high), how high a door might be (average 2m high), but just as importantly how thick a piece of card is needed to represent 5 or 10cm reasonably accurately.

Above is an illustrative ‘sample’ of white card model, simply made to convey a few of the typical things mentioned above .. and not outwardly expressing any aesthetic! However, it is clean and neat .. in other words the making of it looks cared about. One should never underestimate the importance of this! On the other hand the white card model works for a living .. it gets around, it’s handled and it gets worn at the edges .. so there’s no sense in getting too precious about it.

But, there’s nothing to say that the white card model can’t be dressed with some style! The model above was created by Patrick Scalise while a student at Wimbledon College of Art.

VIRTUAL WHITE CARD MODELS

This may seem like a contradiction in modern language but you’ll understand, it’s the best way of describing actual physical scale models made of buildings, structures or landscapes that are never going to exist in their entirety in real size .. but are treated as if they will! If you visit Warner Bros. ‘The Making of Harry Potter’ you’ll see a number of these, alongside other white card models for interiors and other large ‘props’ that were physically built.

Hogwarts was a very clever, highly complex and meticulously planned creation which brought together CGI, real locations, realistic physical models and full-size builds. This white card model is pivotal in giving the countless people involved a clear and immediate understanding of how each part is meant to go together.

 

MATERIALS AND TECHNIQUES

Foamboard

White foamboard is one of the most common materials used as a structural basis for
these models, together with the thinner mountboard. It is light and very easy to cut, though quality and properties differ widely according to brand and price. Its main advantage is in combining ease of cutting with robustness (i.e. it maintains its straightness while still being soft) but its thickness can also be a bonus when defining proper walls (e.g. 5mm at 1:50 scale represents 25cm). It is manufactured in 3, 5 and 10mm thicknesses, though often only the 5mm is stocked in shops. Cheaper foamboards are filled with a relatively coarse-celled polystyrene which doesn’t stand up to solvent glues or spray-paints, whereas the foam interior in more expensive brands may be denser, giving a cleaner, more solid cut edge and perhaps a slightly more dent-resistant surface. The better brands will usually accept even PVA wood glue quite well for bonding. This is certainly true of the superior polyurethane foam in Kapa-line foamboard which will accept even solvent glues such as UHU and spraypaints. Kapa-line remains straight even under humidity (other foamboards are often quickly warped) and it has the added advantage that the paper layers can be carefully peeled off, either to facilitate bending into curves or to use the foam on its own as a material.

Cutting
When cutting through card with a knife a slightly angled edge is inevitable however upright one tries to keep the blade. The thicker the foamboard the more pronounced this can become. This may not always be visible or matter, but better right-angled edges are needed when gluing two pieces together to make a corner. One possible way of solving this is by cutting just half way through on one side, taking the line carefully round (i.e. with a try square) to the other side and completing the cut in exactly the same place on this side. If the foam edge is uneven this can be gently sanded using a sanding block. In fact if one can use a right-angle sanding block gently enough any foamboard edge can be sanded clean and straight. The fuzzy burr of paper which develops along both sides can be removed by carefully ‘scuffing’ with the sanding block at a 45degree angle. Extra care needs to be taken while working with foamboard not to press down too firmly while steadying the sheet as finger-dents are very easy to get.

Joining
Strong PVA glue (always better to use the ‘wood glue’ type rather than the economy-style ‘school’ glue) will bond foam-to-card well but not instantly, so joints often have to be temporarily taped together with masking tape while setting. One should usually allow at least 15 minutes for this. An alternative ‘trick’ is to insert a few short lengths of double-sided tape along an edge to be glued so that these hold the card pieces temporarily but firmly together while the slower glue (alternating in between) is taking effect. Using a solvent glue such as UHU may be quicker, but it dissolves the foam in the standard brands so clean or effective gluing is not always guaranteed. Coating any foam edges first with slightly diluted PVA will solve this and when dry, UHU or sprays can be used on these edges, but it is rather laborious to go to this trouble.

Bending
Whether curved walls need to be made in either foamboard or mountboard the method is similar. The material needs to be cut half-way through in repeated parallel lines (as little as 2mm apart for a tight curve), making it more flexible. But the grooves only work for bending one way, so for example an ‘s’ curved wall has to be grooved in alternate positions on both sides for it to bend properly into an ‘s’. The walls can be surfaced with paper to hide the grooves, but the curve must be secured (in the right curve) before this is done (if done before it will stop it from bending) and it’s better to use permanent spraymount otherwise a thin paper covering will buckle badly.

Other methods include .. if the superior Kapa-line foamboard is used, the paper layer can be peeled off (either from one or both sides) making it much more bendable without having to score the surface. Perhaps an even easier alternative for achieving curving walls is to use a dense foam sheet such as Plastazote, which is spongy and very flexible, or a thin styrene plastic (see below).

I have to say that I have mixed feelings about the use of foamboard for these models. On the one hand a good, robust, polyurethane-core foamboard is invaluable as a lightweight baseboard .. but if a cheap polystyrene-core one is used it is liable to warp badly over time and ends up showing every finger impression! This is also the problem when using foamboard for wall construction. It has to be handled very carefully, and unless one has taken the trouble to practise with the material for a while before trying to cut clean edges or door/window openings .. it just doesn’t look good! It’s true that it can be a massive time-saver in terms of representing appropriate wall thicknesses, as mentioned earlier. I would suggest you use it sparingly until you’ve mastered how to achieve perfectly clean, straight cuts.

White mountboard

It is essential to have white mountboard (or equivalent white card between 1-2mm thick) i.e white on both sides rather than white/black. Otherwise, the model can become chequered with distracting areas of black. In any case white mountboard tends to be cheaper and some brands are softer to cut. As with foamboard there are many similar brands of white card with a standard mountboard thickness (c. 1.4mm, or 1400microns as it’s sometimes written) and these will vary greatly in hardness and quality. Matte is definitely better to choose (there are some semi-glossy types), and avoid white card which has a noticeable layering inside (a bit like plywood) because this is likely to be the toughest to cut! The same is true generally of ‘greyboard’ or recycled grey or brown cardboard which is hard and full of gritty particles.  Most of the softer forms, such as the standard Daler-Rowney mountboard sold in A1 size sheets are fine for perhaps most of the work ..walls or simple cut-outs.. but unsuitable for more delicate structures such as railings for example, because they are too thick in scale and will break apart if cut too thin.

Cutting
As a general rule when cutting anything by hand with a knife it is always better to take things carefully and slowly. There is never any advantage in being able to cut right through in one go even if that is relatively easy. A straighter, more right-angled and
cleaner cut is almost always achieved by starting carefully with a very light guiding cut and following through a few times, increasing the pressure gradually. As with all straight cutting, it should be done against a flat metal ruler (non-slip, or with masking tape along
the underside to make it so) and positioned so that the main light source is falling into the cutting edge, so that the marked line is not obscured by shadow. It is surprising how many people who might in other respects be very able with their hands find it quite difficult to cut a straight, clean line. From my experience of witnessing people trying to cut a straight line (must be easily in the thousands by now!) I’ve come to the conclusion that the problem lies in not properly ‘feeling’ the straight edge of the ruler enough to stick with it. It may really be this simple! The best advice I can give (apart from the points above) is to spend a little time getting acquainted just with what it feels like to press the scalpel blade firmly against a metal edge and move along evenly. It may also help to say that the scalpel blade is ‘meant to’ bend a little with the pressure of being pushed against the ruler and that if it doesn’t its always liable to wander.

Gluing
White Pva glue is always the best and cleanest option when gluing almost anything porous, like cardboard. Strong Pva (a.k.a wood glue, such as ‘Evo-stik wood’) invariably gives stronger and cleaner joins and a good quality Pva can be surprisingly quick. When gluing edges the PVA must be used sparingly (and excess wiped off) for the quickest results on card. Especially if two larger pieces are being laminated (i.e. glued surface-to-surface) only spots of glue are needed to hold them firmly in place otherwise the water-based glue will cause warping if spread on too liberally.

If .. for whatever reasons of your own .. you prefer to use UHU, you must be able to control it! Unfortunately the UHU tube nozzle, the consistency of the glue and the way it comes out, are not designed for really precise control .. such as is needed when trying to apply the glue to a thin edge of card for example. Some practise is needed first. One tip is that if you want UHU to stick firmly more immediately .. almost as superglue does .. you have to apply the glue and position the piece down as you normally would, pressing firmly, but then lift it up again just a few millimetres. This will ‘string’ the glue slightly, and when you press the piece down again the bond will already be much firmer and will not need supporting.

Thinner white card

It is essential, if you want to keep in scale, to have recourse to something thinner than mountboard but still strong enough to stand up on its own if need be. It also helps if this card doesn’t fragment (divide into layers) so easily when finely cut. Usually the thin white card sold in art shops is not labelled by thickness but according to its weight per square metre. College shops in the UK tend to stock inexpensive thin white card from the art supply firm Seawhite in 200, 300 or 600gsm weights. The 300gsm is roughly 0.5mm thick and the 600gsm 1mm thick. These are quite strong, but also suitable for delicate cutting.

If the thin card is reasonably strong (i.e. ideally within the 200-300gsm range) it can be used for small constructions. Wall fixtures which need to be given their true depth, such as the radiator or the exit light above can be simplified as boxes, which can be scored and bent into shape. The doorframe, skirting board and power conduits can be left as drawings since they are well below the 5cm rule.

Stencil card

This type of card is also known as ‘oiled manilla’ and is meant for making very fine-cut stencil shapes. The manilla card has been impregnated with linseed oil which prevents it from fraying or breaking so easily. This treatment also gives it a slightly waxy composition, making it easier to cut and ensuring a very sharp edge. Although it is by far the best for intricate work .. especially to convey repeated balusters, railings, delicate window frameworks etc .. it is not ideal for strictly ‘white card’ models because of its warm ochre colour. If used it needs to be covered, sprayed or painted .. unless the whole model becomes a similar colour! Although it contains oil it can be painted with water-based paints or glued using Pva quite easily. It will not warp as much as other types of card when painted. However, if it is used and needs to be made white I would recommend spraying it first with Simoniz white acrylic primer. This won’t eliminate all the colour, but most of it, and more importantly it will seal the surface so that once the primer is dry after a few hours, more water-based whitener such as white acrylic or gesso can be applied without the structures warping. More about what’s achievable with oiled manilla can be found in Working with stencil card which is under ‘constructing’ in the Materials section.

The 1/4 inch (1:48) scale white card model for ‘Boardwalk Empire’ not only fully clarified the space but also communicated much of the ‘look’ due to the inclusion of the signage. Courtesy HBO ‘Boardwalk Empire: Designing an Empire’.

Acetate

Thin acetate sheet is the most available clear plastic to use for representing window glass. At 1:50-1:20 scale this doesn’t need to be very thick and usually the slightly stiffer version of two commonly sold as A4/A3 sheets in graphics or copy shops (for writing or printing on to use for overhead projection) will remain flat enough.

Cutting
Acetate cuts easily with a scalpel but if need be thicker sheets can be scored and snapped cleanly. If scored lightly then bent on the score line it will stay together as corner, which is useful if trying to represent a glass construction without the messiness of having to glue edges. One can’t mark on acetate with a normal pencil so either the shape to be cut needs to be drawn on paper and used as a template underneath or the surface covered with masking tape and lines marked out on that.

Gluing
If gluing becomes necessary i.e. for attaching to the backs of window frames, small strips of double-sided tape are much cleaner than glue. Superglue for example will ‘fog’ acetate around the area glued while both the ‘cement’ intended for plastics and UHU tend to be difficult to control. A third alternative (but only if gluing acetate to another plastic such as styrene) is the thin plastic solvent available for melt-gluing a range of plastics (e.g. ‘Plastic Weld’ or ‘Extrufix’) which has to be brushed onto a joint from outside. This is generally much cleaner because any excess solvent will evaporate

If acetate is used for the windows the frame divisions can be conveniently drawn on, and as I’ve mentioned, thin railings can also be represented in the same way. I would recommend matting both sides of the acetate first by rubbing with a sponge scourer on both sides. This eliminates too much reflection and it also provides a better key for ink. I’ve found that circular rubbing creates too many visible scratches whereas light diagonal rubbing (reversed on the other side) will give a better overall result. Once treated in this way, a Rotring pen will draw smoothly on the surface and give a bold clean line .. but the ink does not dry completely smudge-proof. The ‘OHPen’ above, meant for drawing on acetate, produced the cleanest and safest result, but surprisingly the cheap Bic biro (third try from the left) also managed a clear and permanent line.

As mentioned, since it is not possible to mark out on the acetate in pencil (even when ‘matted’), this needs to be done on paper and then traced from.

Plastazote

This is a flexible foam (halfway between hard foam and ‘cushion’ foam) which is available in many thicknesses, densities and colours. Most people will be familiar with the similar, brightly coloured ‘hobbyfoam’ sheets for children which usually range between 1-3mm thickness. The material may also be familiar from exercise or camping mats. Although very soft it can be cut quite cleanly with a sharp scalpel though it can’t be sanded. At an appropriate thickness it can be ideal for curving walls for example, or even for building up a run of curving steps.

Gluing
Plastazote cannot be glued with Pva and even UHU may not be strong enough. A rubber contact adhesive such as ‘Evo-Stik Impact’ will be needed. This has to be lightly applied to both sides, left for a few minutes and then pressed together (UHU can sometimes be used as a contact adhesive in the same way). This has to be done carefully because there is no chance of repositioning. Some brands of this type of foam glue very readily with superglue.

Styrofoam, expanded polystyrene and PU foam

For some structures to be represented it’s easier and quicker to make solid blocks rather than having to construct boxes from a sheet material. Since white card models
don’t necessarily need to be permanent, these light, easily-worked, so-called ‘rigid’ foams may be an option. Styrofoam may be familiar as the light blue sheets (although styrofoam comes in other colours according to different grades or densities) made for wall insulation and commonly used in theatre and film workshops as a rapid carving material. Styrofoam is very finely-celled so it sands very well without crumbling .. using a sanding block it’s possible to get smooth, sharp-edged shapes fairly easily. But styrofoam is of particular benefit for achieving curved, streamlined or organic forms. Regular acrylic or acrylic gesso are best to use for painting it white, since spray paints will dissolve the surface. For more on how to shape styrofoam, including concave as well as convex forms, see my article Shaping styrofoam under ‘shaping’ in the Materials section.

Expanded polystyrene is basically the same substance but formed differently and the cells are much larger. This is made only in white and will be most familiar as hardware packaging material and ceiling tiles etc. This common ‘expanded polystyrene’ is often shortened to ‘EPS’ whereas styrofoam is officially ‘XPS’ meaning extruded polystyrene.

Polyurethane foam .. often referred to as ‘PU foam’ .. is usually found in white or beige, and is often a harder, denser rigid sheet foam than the others. It will resist the solvents in glues and spray-paints, though these will still work well to bond or cover it. Rigid PU foam is mainly available from suppliers of resins and fibreglass materials. But, nearer to home perhaps, some regular foamboards are made with a polyurethane core rather than polystyrene and the paper coverings are easy to peel off cleanly to use the smooth foam as a constructional or shaping material. Examples are Kapa-line foamboard and London Graphic Centre’s Premier Polyboard.

Cutting
These foams are very easy to cut with a knife (or hot wire cutter, except PU foam) and both styrofoam and PU foam can be sanded effortlessly to a smooth, sharp finish even for very small forms. This is not the case with polystyrene because of its much larger cell structure. These tend to break up or can’t be sanded down below a certain size. All can be cut on a band saw, but failing this the best way to ensure a straight cut right through is (as with thick foamboard) to start cutting half way through on one side, take the line round and complete from the other side. Neither a scalpel nor Stanley knife will go very deep so often a sharp penknife, fruit knife or serrated bread knife will serve better. The rough edge produced can easily be sanded smooth with coarse sandpaper on a sanding block.

Gluing
Whereas PU foam is not affected by solvents and can be glued quite effectively with UHU, contact adhesives or even superglue, styrofoam and polystyrene require special ‘foam friendly’ glues such as ‘UHU Por’ or solvent free (I recently found that Gorilla Glue will also work very well since it is polyurethane). Strong Pva wood glue should work with all though takes a lot longer to set. Often it is much easier to tack foam pieces together with double-sided tape which, if pressed together hard enough, will often hold just as well as gluing. Another form of glue which styrofoam seems to accept is spraymount, especially effective if sprayed lightly on both surfaces like a contact adhesive.

Foamed Pvc and styrene

Although foamed Pvc sheet is not so easily obtainable (at least not from art shops) it has excellent properties, being somewhat easier to cut than even some forms of card while remaining much more durable and resistant to warping. The thinnest gauge (1mm) is ideal for delicate cut-outs such as windows and railings. The best brand of foamed Pvc for this kind of work is ‘Palight’, which is one of the smoothest and softest to cut ( or the similar ‘Palfoam’ which is even softer and supposed to be cheaper). Usually the minimum quantity one can order is an 8x4ft sheet (1220x2440mm) which can be quickly delivered, but if one accepts this the price of 1mm or 2mm Palight can work out cheaper than most forms of cardboard. A good online source for ordering/delivery is Bay Plastics www.plasticstockist.com (the 1-2mm white foamed Pvc included in the online catalogue is the cheaper ‘Palfoam’ rather than Palight). Recently though the 4D modelshop in London have started stocking 1mm and 2mm Palight in small (300x600mm) pieces, ideal if you just want to try out a small amount first.

Another plastic, styrene, is also available in sheet form but much thinner (down to 0.25mm) and is also often more suitable than card for slender cut-outs but is denser and harder to cut than the foamed Pvc. Both will allow a certain amount of bending. They are both used extensively in architectural model-making in place of card or wood and are obtainable either from specialist model-making shops such as 4D modelshop or suppliers of plastics (such as Abplas in London).

Gluing
Superglue works very well on both plastics for a quick, strong bond but working with superglue is a practised art because there is no time for repositioning before the glue takes. An alternative when working with these plastics (also generally a much cleaner one) is to use a plastic solvent such as ‘Plastic Weld’. Different from the usual gluing process, the pieces to be glued have to be set up firmly in position first and the solvent is then brushed into the join. Only a little is needed, which is drawn into the joint by ‘capillary action’. There it melts the plastic surfaces and effectively fuses the two pieces
of plastic together. Any excess solvent outside the joint quickly evaporates resulting in a very clean joint. ‘Plastic Weld’ (as with other brands of dichloromethane solvent) works best on styrene plastics but in tests I found that it did work on the foamed Pvc though it took longer to set. If this doesn’t take, the ‘gluing from outside’ method will work just as easily with thin superglue.

For more information on working with Palight foamed Pvc together with illustrative examples click on ‘Palight’ brand foamed Pvc under ‘constructing’ in the Materials section.

I maintain an up-to-date record of the best or most convenient places to get these special materials in Updated sources/prices of specific materials which can be found in the Suppliers section.