Balsa Foam - Sculpting Made Easy!

Written by Frerik Noordhuis

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Balsa Foam - Sculpting Made Easy!
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Imagine being able to make your bases like these...Frerik shows how you can!

Feature Competition Winner - January 2011

Balsa Foam
What is Balsa foam? It is a dense, rigid, expanded plastic made from a phenolic resin. It was developed specifically for model making and is ideally suited to carving, sculpting and coating. Its tight cell structure also makes it effective at holding fine detail.

It comes in three types... I, II and III. Type I being the softest and type III the hardest, meaning type I is easiest to sculpt and carve but also easiest to dent or damage. Types II and III are harder, but also strong enough to use in vacuum forming.

It can be purchased in different sizes: 9 x 6 x ½ inch or 12 x 9 x1 inch or 12 x 9 x 2 inch being the sizes I use mostly.

Three types - which one to use?
As it says above - Balsa Foam comes in three types, or rather types of density.

Type I being soft, easy to work with...even with blunt tools or fingernails. The downside of this is that it damages easily when being handled, and is too soft to use as a master for example a casting process.

Type II is far more rigid and denser. Still easy to carve or scrape, but a little harder to use a stamp on this one, as it requires a little more pressure. It is better suited for the casting process, but since it still has an open structure, it needs sealing before making a mould from it.

Type III is the hardest, and can stand much more handling. You are able to produce really fine details in this material, but it needs to be carved rather than stamped or scribed. Thus needing more time to produce a building for instance.

My choice when making a one-off building for a diorama? Choose the softest type...it also happens to be the cheapest one!

When making a building you need to handle a lot, or when wanting to reproduce it and use it as a master...go for type II. Only when wanting to make wafer thin details on buildings like incorporated shutters should you choose type III.

Sources:
Direct from the producer:

American Foam Technologies

From a UK Distributor:

Antenocitis Workshop

Or down under:

Bunyan Films

CAUTION!
When working with this material there are a few things to keep in mind. Balsa Foam is non-toxic, it is made from non-toxic materials unlike most resins we use in modelling! However, when sanding or turning or even scribing Balsa Foam, it can produce large amounts of fine dust.

This dust can irritate your eyes when it gets into them, and I can imagine that like any fine dust such as MDF dust, it is bad for your health when inhaled!

So take care when doing a lot of sanding, and blow it away from you when working,
or like I have seen others do, mount or keep the vacuum cleaner close to or on the work bench.

Balsa Foam also can rust your tools... quickly! Leave a scalpel blade on or in it just overnight, and it will be rusted overnight!

Tools

Balsa foam can be cut with a knife, or a large coping saw or even a small razor saw. It can be sanded smooth, or roughed up. It can be carved with hobby knives, or sculpted with one. It can be scribed with almost anything.

Firstly, you will probably want to cut the basic sheet down to manageable sizes, or whatever the size of your wall or base elements are going to be.

For large pieces, use a coping saw or even a band saw...making sure you clean the dust off afterwards because of the way it can affect metal. For smaller pieces or cuts the razor saw or a long blade on a hobby handle, or even scribing the cut through and through with the back of a hobby knife will suffice.

For sculpting you can use a set such as that shown below from X-acto or Proedge....

For scribing, similar sets can be obtained. The top four tools shown below, are in a set, whilst the bottom three are separate items.

Here's a close-up of these last two, that I use the most. A seam-scraper, and a panel line scraper.

Then there are needle files...use cheap ones for Balsa Foam!

And there are various embossing tools you could use...easily made yourself from rounded off nails, brass wire or plastic, etc.

Also most usefully, an old stiff toothbrush, and a soft brush to wipe away excess dust without damaging detail!

Making a scribing tool
The first technique you will probably use is the scribing technique. So you'll need a tool. As you can see, I have a few of those, but it is real easy to make one yourself, and then a few more as and when to suit your needs.

You need - a knife holder and a paperclip.

Fold the paperclip open - don't cut it just yet, as this is easier to hold! Hold it against a cutting disk in your motor tool. Grind the blunt tip to a more or less sharp one...it doesn't have to be as sharp as a needle...you'll find different ones more or less comfortable and easy to work with. This can also be done with a file, should you not have a motor tool available.

Next...cut off a length and insert it into your handle...voila! A scribing tool.

As you experiment with different scribing techniques, you might want to make a few more - thicker or thinner wire, blunt ends, differently bent wires...or even straight strips of material.

Eager to start
When you first get your hands on some Balsa Foam, you might be tempted to start straight away...but first try practicing on a small piece. Start out by scribing some bricks for simplicity. If you are not satisfied, sand down the top layer, and start over!

When you feel ready to do a project....make a plan!

Ask yourself these sorts of questions:

What do I want to make? How can I make it more interesting to the viewer? What is the scale I am going to be building it in? What size should the doors or windows be?

Don't just scribe in the bricks... think deeper, add layer, add interest!

Example 1
A project I worked on consisting of a stone arched bridge.

Notice the cutting back of a few bricks to add interest.

A small house. The picture below is actually of a ceramic copy, which was an abandoned project since we were unable to cast it without lots of air bubbles in the bricks.

Example 2

Here is an example of how planning and drawing is applied to a definite project. This is a one-off original made from Type I Balsa Foam.