Tutorial: Designing pleated forms 1

In my last tutorial, I gave step-by-step instructions on how to fold a vase using a pleated folding technique.  In this tutorial, I’ll talk about how to design your own pleated vases and bowls.  This post will focus on how pleated folding works, and later I’ll write a tutorial on how to calculate the correct dimensions for any shape.  To start, here’s the pleated vase from my last tutorial:

Why does this crease pattern fold into that shape?  Let’s start from very simple crease patterns and work our way up.  Imagine that you took a long piece of paper and accordion-folded it, using equally spaced mountain and valley folds. All of the layers of paper end up on exactly top of each other to make a very narrow strip of paper.

Now imagine that instead of the folds being equally spaced, the pattern goes something like this: large gap, mountain fold, small gap, valley fold, repeat.  If this pattern is folded, the layers won’t end up exactly on top of each other.  The paper will be somewhere between the length it was when the folds were equally spaced and the length of the original strip of paper.  As the small gap gets smaller and the large gap gets larger, the folded strip of paper gets longer.

Now let’s take those three examples and attach one end of the paper to the other end to make a tube.  In all three examples, the paper starts off the same length.  In the first example where the folds were equally spaced, the paper forms a very narrow tube.  The more unequally spaced the folds are, the wider the tube is.

From these simple examples, we can understand how the pleated forms work.  Just like the accordion-folded examples, the crease pattern below is based on alternating mountain folds and valley folds.  In this example, the valley folds are straight and the mountain folds are curved.  Either the mountain folds or the valley folds need to be straight lines; otherwise the form doesn’t collapse cleanly.  We can think of the shape as a tube like our last set of examples, but in this case the width of the tube changes.

At the bottom edge of the crease pattern, the mountain and valley folds are equally spaced.  Based on our accordion-folded example, that means the tube should be very narrow.  And that’s what happens: at the center of the base, the layers of paper all match up, closing off the base.  About a quarter of the way from the top edge, the mountain and valley folds in each pair are almost on top of each other.  Here we expect the tube to be very wide.  Again, that’s what happens: the place where the mountain and valley folds are closest together becomes the widest part of the vase.  At the top edge of the crease pattern, the mountain and valley folds are somewhere in between – not evenly spaced, but not on top of each other.  The top edge of the crease pattern becomes the rim of the vase, which is intermediate in width.

Here’s one more example.  In the crease pattern below, the folds are equally spaced at both the top and bottom edges, and there are two places in between where the mountain folds curve so far out that they touch the valley folds.  So in this model, both the top and the bottom are very narrow and there are two widest points in between.

Stay tuned for my next tutorial on how to figure out the dimensions for the crease pattern.