Making walls – Part 3

In Part 1 I introduced a special method of building a model wall which involves ‘laminating’ a soft foam layer onto a cardboard (or Pvc) cut-out. This makes for a much stronger (also lighter) construction generally, as well as making it easier to work to a required thickness without the problems involved with cutting through other thick materials and keeping the edges precise. The third advantage is that the foam on one side lends itself more readily to heavily textured effects (for a possible exterior) whereas the harder layer on the other side is a suitable base for interiors.

simple interior wall drawing

This Part 3 follows directly on from Part 1 and looks at applying details to the interior side, in this case the simplest version drawn above (Part 2 had jumped ahead a bit, looking at more ambitious effects with Kapa-line foam). Drawing up .. always/however simple the task/without question .. is the first requirement! Finding the right scale of material to convey a convincing look, with an appropriate visual weight or lightness, is the next requirement. Doorway and window frames, skirting board etc. can be built up using a variety of materials .. card, wood or plastic .. as long as they can be cut cleanly and are thin enough for the scale intended. For example here the scale is 1:25, so standard mountboard (at almost 1.5mm thickness) is really far too thick. Mountboard is also too fragile when cut into very thin strips (the edges don’t stay sharp and the top layer is also likely to separate). Much better results can be achieved with either stencil card, 0.8mm obeche wood, 0.5 -1mm styrene sheet or, as I’m using here, 1mm Palight foamed Pvc.

Palight foamed Pvc doesn’t come any thinner than 1mm but it just about works for wall details in 1:25 scale especially if the edges are softened. That’s the other big advantage over card .. that it can be sanded, either to shape it or neaten up edges. It can also be given a convincing woodgrain texture, and that’s what I’m doing first below with a small piece of the Pvc. Here I’m using 120grit sandpaper on a sanding block, which needs to be pressed/dragged firmly along the plastic in one direction. Coarser sandpaper (i.e. up to 40grit) can be used for a larger scale effect.

graining Pvc

The effect doesn’t show up that much until it’s rubbed or washed with acrylic or woodstain, shown by the collection of samples below.

wood simulation

Here I wanted to build up the doorway and window frames in two layers, and position the first layer very slightly outside the edge (rather than right on it) so that there is an ‘extra’ little step visually. To keep the positioning regular I drew guidelines (i.e. the outer limits of the frames) around the openings.

marking frame outline

The art, the science and ‘sense’ of cutting

Below are the strips cut to make the first layer. I’m sure I must have said many times that there’s a whole little book to be written just on cutting with the scalpel! At the very least, anyone not practised in cutting needs to consider it a subject in itself which needs to be rehearsed, explored and ‘made peace with’ as far as possible before being able to do anything else. Scale model-making of this kind is so dependent on being able to cut a straight line in the right place. It sounds so simple .. but it’s not! It can’t just be taken for granted that everyone will be able to do this with just a little practise and often people who could otherwise become excellent makers are put off the whole idea of model-making just because this one aspect is never really ‘conquered’. Here are a few guidelines:

If you’re using a material for the first time you should take a while just to get a sense of how it cuts i.e. starting with how steady the metal ruler will lie on it, how resilient or giving the surface is to the initial pass with the blade, how many passes are needed to cut through cleanly without excessive pressure. If you don’t feel confident that the ruler will stay where you’ve put it, you either need a better ruler or you need to do something so that it will grip better. Flat steel rulers will certainly need a strip of masking tape on the back at the very least but sometimes this isn’t enough so pieces of double-sided tape could be added provided they won’t damage the material.

You should also rehearse what it feels like to run the tip of the blade steadily along the metal edge, without necessarily cutting at all. It should feel locked there, able to run freely along but not to depart from the edge. The scalpel blade is slightly flexible and it should be pressed hard enough into the metal edge so that it flexes just a little.

There are no special prizes for being able to cut through in one go! The first pass with the knife should simply be to establish a guiding ‘scratch-line’ which only has to be deep enough to be found again with the tip of the blade. One’s focus at this stage should be more on the edge of the ruler than the material to be cut. Pressure comes afterwards, once one’s established this line and it shouldn’t matter how many passes it takes to cut through. If you’re having to press so hard to get through the material that you can’t control the straightness of the cut anymore it means one or more of the following:- the material is too tough or thick to be cut with a scalpel and you will have to try with a Stanley knife or failing that a saw; you can turn the sheet over and try cutting in exactly the same place on the other side (when cutting thick materials it’s the friction on the blade that becomes the problem and starting ‘new’ from the other side often works); you need to build up some more strength in your hand and arm through practise.

If, for whatever reason, the ruler moves while cutting, don’t try repositioning it by eye. Put the tip of the scalpel in the beginning of the line you’ve started and slide the ruler up against it. Holding onto that position put the tip of the scalpel in the end of the line and move that end of the ruler against it. You might need to adjust, beginning and end, a few times.

It’s worth asking yourself consciously whether you’re working under the best conditions or whether they can be very simply improved? For example .. is the cutting matt flat and smooth or is it more like a Jackson Pollock? Can much of this be scraped off? Is the cutting matt really flat on the table or are there small bits of scrap under it? Have you really got enough proper light to work by? .. in particular, can you see your marked line clearly enough or is the edge of the ruler casting a shadow over it?

Usually with thin materials (i.e. up to 1mm) the angle of the cut edge, in other words whether it’s at a right-angle to its surface or not, doesn’t matter so much. Generally, if one’s holding the scalpel normally it will be fine. But if over 1mm thick it can matter, especially if the edge is to be glued on something else at a right-angle. If using foamed Pvc or wood it would be normal practice to straighten the cut edge using a sanding block and this will even work with foamboard or some types of cardboard. Even so it’s best if one gets used to holding the scalpel upright in the first place. It’s much easier to maintain the knife upright if you can actually see the angle while cutting, i.e. by cutting the line in the direction straight ahead of you rather than side to side. Especially when cutting longer lines it’s usually better to stand up for this so that you can reach over the work properly and use your own body as a ‘measure of uprightness’.

cutting strips

If you’re using a standard surgical-type scalpel (i.e. Swann-Morton No.3, which I would always recommend) the best blade to use with it is the ’10A’. It’s the most general-purpose but also the most precise. Changing the blade (i.e. when it gets blunt) can be a nightmare with a new scalpel because the fixing is often very tight, making it hard to slide the blade either off or on without fear of injury. The only way to solve this (until it wears down a little with use!) is to file into the blade channels a little. Below is not intended as a solution to this, but it does help to know that blunted blades needn’t always be replaced. They can quite easily be sharpened on a piece of ‘wet and dry’ or Emery paper (usually best 600-800 grit) by stroking the blade firmly at a shallow angle, a few times each side. It’s usually only the very tip of the blade that gets blunt so it’s best to focus on sharpening just this small part, flexing it a little into the paper.

sharpening scalpel

Here .. back to the actual work now! .. I’ve chosen to mitre the pieces of doorway/window frame together as they would be in reality, that is, to cut the joining ends at a 45degree angle (as picture frames are also usually made). In the real-scale world this is done because the profiled strips (i.e. showing a particular ‘stepped’ shape when looked at on end) are usually manufactured as solid strips rather than pieced together in layers and joining them on a diagonal is the only way of making the profiles fit. This also becomes important if the grain of the wood is to be a visual feature; joining on a diagonal is the only way to make this look good. In the model where, as here, it’s easier to build those profiles up in separate strips .. no, often it may be easier not to have to mitre, if the join lines aren’t too visible .. but here I’ve also chosen to put a fake grain on the Pvc, so mitre joins are better in this case.

Below, the easiest way to cut a 45degree angle is to use the grid of squares which can usually be found on the cutting mat, placing the end of the strip within a square and spanning from one corner to the other with the scalpel blade. Because the Pvc is soft the end could just be chopped by pressing the blade down, but I prefer just to make a guiding mark this way but then cut by drawing the blade across in the usual way. The other reason for this is that it’s better if possible to put a slant on the cut (shown by how I’m angling the blade in the photo) which will help in getting a tighter join later.

cutting a mitre

There is little alternative to using superglue when working with Palight foamed Pvc. One of the main advantages of using superglue is ‘instant gluing’, but anyone who’s used it knows that this can also become its main drawback .. the fact that one usually can’t slide a piece carefully into place and reposition it while it’s gluing. One has to develop little strategies to compensate. For example, rather than cut both top and bottom of the strip being glued in place below, I’ve found it better just to cut the mitred top and trim the bottom off (cutting from the other side) once glued in place.

gluing in place

The cutting and gluing of the pieces follows the form round, as below. Here I have cut a mitre on the second piece (also left for the moment as a longer strip) and am checking its fit before anything else. If this is fine, the position of the mitre at the other end can be marked in pencil while the strip is held in place. This piece has to be cut to size before gluing in place, whereas the third and final length can be left long when glued (as before) and trimmed afterwards.

moving round

Almost exactly the same is done for the window, remembering that the frame is cut off along the bottom edge of the window opening because the sill protrusion needs to go there (window frame wall mouldings don’t travel right round like a picture frame as a rule).

allowing for sill

Because Palight Pvc is relatively soft the surface takes grooving or embossing very well. Extra detail can be added to the frame this way if needed. Below, I’ve used an embossing tool (the tip is smooth and ball-shaped) to make an even groove without tearing up the surface. In fact by pressing lines carefully in the soft plastic in this way one can create the suggestion of a number of steps to the moulding without actually having to layer thinner strips on top. I’ve done it here (and it can be seen better in the last photos) because I wanted heavier shadows. The process is just the same used for the first layer.

embossing detail

Often in reality the whole window sill is a thick plank of wood which juts out a few centimeters into the interior space, the edge of which is rounded or at least softened. Here it is conveyed by a thin strip applied to the surface. Below, I am using the piece of 2mm thick Pvc left from cutting the door opening, rounding one edge first using the sanding block. When suitably smooth and even this can be cut off as a shaped strip, cut to length and glued in place.

rounding edge

The final part of this stage in the interior decoration was cutting another strip of 1mm Pvc for the skirting board. Before cutting the strip off the sheet I straightened and softened the top edge with the sanding block and embossed an extra line. Here I am using the sanding block upturned as a guide for gluing the skirting board strip right on the bottom edge of the wall. The sandpaper surface helps the block to grip in place for this.

using block as a gluing guide


The doorframe is always put in first and the skirting board inserted up against it. The doorframe is also usually thicker (at least at it’s outer edge) than the skirting board. The slope of the doorframe moulding i.e. just as a picture frame is thicker on the outer edge, is meant to perform the same function of drawing our focus in on the door. The skirting board has a few functions, mostly inherited from the past. It helps to define the wall, divide it and offer a visual transition from one plane or element to another, in the way that all other wall mouldings (doorway and window frames, cornice and dado area) are meant to do. But it’s principally there to hide the ragged join between whatever the floor is made of or covered with and the walls, especially floorboards where a gap is necessary to allow for wood expanding. It also used to function as a buffer, to prevent furniture from scuffing the walls.

completed wall decoration

Priming and painting the wall or adding wallpaper, adding door and window, making a shaped cornice, painting or staining the ‘woodwork’ etc. .. all these things will follow at some point ….

5 thoughts on “Making walls – Part 3

  1. Hi David,
    Great tutorial as usual. I use the same sharpening technique on my SM blades but I used to find that they would get small burrs on them. So I overcame this by making a strop by cutting an old suede coat up and gluing sections on a 5 ply board rectangle about 20×8 cm (soft suede side up) I just rub the blade on this and it removes any of these microscopic jagged edges that can cause the blade to cut roughly on small thin sections. This I learnt from my bookbinding guru.

      • Three options! If in London you can get small sheets of 1mm or 2mm from 4D modelshop, or larger amounts from Abplas (but make sure they’re selling you Palight). If not in London get it online from Bay Plastics. You’ll find details and addresses on the ‘Suppliers’ page (above) esp. in ‘Plastics and foams’ section.

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