The Little World

I’m not going to deal with how much you eat and what it does to your waistline, nor to whether your business is flourishing or failing. These forms of expansion and contraction form no part of the Little World. What does, however, is how various materials behave under various stimuli – heart, cold, damp, and adhesives. It can make or break a model.

a. Every time your model gets hot it expands – but its parts may not expand evenly or in time with each other. And this puts a strain on joints and seams that you may have worked hard to fill. It’s not unknown for invisible stuff to become visible again, to your annoyance.

I’m not suggesting that everything you do needs to be in a climate-controlled bubble…but try to avoid the extremes of temperature while building or displaying.

b. That goes for paint coats and other treatments.

c. Expansion and contraction also occur while adhesives are at work on your model. The classic trouble is when applying some PVA or other water-based glues to paper or cardboard. They may penetrate the fibres of the paper but they will cause swelling as they do – and things may bow. Then as the glue loses water there is a contraction that can warp the strongest under-base.

To counteract this, I sometimes glue both faces of a piece of card with similar paper to apply even tension on both sides. It works surprisingly well if thee areas of pressure are equal.

This same idea applies if you are painting MDF board with water-based acrylic paint. If you cannot coat both sides of the MDF initially, do so as soon as the front face does its initial drying. The stresses on the MDF will be equal and it will remain flat.

d. Step aside occasionally and choose an acetate cement like that used for balsa wood models. It may dry firmly without triggering paper curl.

e. If you are almost sure you’ll have a curling problem, paint the paper with a thin cyanoacrylate glue and let it cure off – this seals the fibres and stiffens the piece. This will also save strip wood from turning into a banana.

But enough of this idle speculation. Science to the fore! Tomorrow we test the actual warpage with the actual glues and actually prove something…