Little Things: What’s the Crack?

I don’t own a car. As a result I tend to walk everywhere. I like it.

It gives me an opportunity to look at stuff. Stop and look at stuff. Really look at stuff.

Cracks are a prime example. Time and time again I see modellers producing fantastically engineered builds with a glaring (to me at least, and to you by the end of this article) mistake. Their cracks are wrong!

Cracks, when I sat down and thought about it, are interesting things. They are the results of usually astonishing forces pulling apart a solid thing. Things that don’t want to be pulled apart and resist right up… to… the… tipping point and bang! You have a crack.

They have certain characteristics, and one of these is that glaring mistake you’ll curse me for every time you see it from now on.

Cracks go edge to edge. Always.



My walk to work takes me past Manor Castle, and the pathway along side of it has been around a long time, it’s seen some shit. Slabs of stone have to be around a long time to start cracking. Here’s a shot of a random flag:

Every crack starts at an edge and travels till it meets another edge (or a crack – a new edge).

Some other observations:

They form because the stone has been flexed – either by the ground falling away from underneath and weight applied from above, or pushed up from below. Cracks splinter out away from these pressure points but they don’t stop till they hit an edge. Hard impacts like the ones from above can originate in the middle of a slab (which is really an edge formed by the other cracks) but will always end at an edge.

Occasionally, you’ll see this sort of thing:

Where a crack will turn mid break but STILL end on an edge!  These usually form when the ground underneath the corner of the slab falls away and pressure is applied to the corner from above.

The phenomena isn’t just limited to flag stones, any solid block can crack – and it always goes edge to edge. Even in composite matrials like concrete – so long as it forms a solid.

“Ah”, you’re thinking, “, but I’ve *definitely* seen cracks stopping mid way through things!”

Yes, you have have. But not solid things. And it’s not a crack, it’s a tear! You see it in things like tarmac which although appears solid is really just a very, very slow moving goo (stone doesn’t melt and stick to your tires in summer).

When it comes to modelling cracks. Try to imagine the point of force and radiate out from that point. The stress fractures can pass between stones so remember to carry a few lines on over multiple stones.

Once I’ve cut the cracks into my material I’ll often push the slabs around the cracks in a little to simulate an impact point.

(Read the Ruined Bridge build log)

It’s very easy to over do it. I like to think the original builders knew a bit about laying slabs on a good foundation. You don’t need to crack every tile.

(Read the Modern ruins build log)

This is a bit of a change in pace from my usual build articles. I hope you like it – I have a few more planned. Observation is key to effective model building, even when you’re building the unreal. The little details that *don’t* catch the eye and pull you out of a scene are what matters.

Here’s to the little things! Happy modelling.