This is one of my favourite structures as it is so easy to create.  You start off with a simple double cloth, on 8 or more shafts, with one cloth being in non-shrinking yarns in shrinking yarns on 2 shafts (plain weave), and the other cloth being on 6 or more shafts (patterned weave).  You can choose to make the ratio 1:1 or change it to 2 of the non-shrinking warps  to 1 of the shrinking warps, or expand it further to other ratios depending on the effect you want to achieve.

You use plain weave for the non-shrinking warp, and whatever structure you like for the patterned warp.  You can thread the patterned warp in whatever threading pattern you wish, using blocks, or straight and pointed threadings, advancing or networked threadings.  When designing your weave structure for the shrinking cloth, you need to bear in mind the length of your floats and how much you actually want the fabric to shrink. 

With ratios of 2:1 or more, you are going to have much longer float lengths in the warp and weft of the patterned cloth.  Even plain weave will give a certain amount of shrinkage as the floats are twice as long as normal 1:1 plain weave, and even more in greater ratios.  Twills are good structures, and even longer floats such as waffle works brilliantly well.

What creates the puckering in the top cloth is the stitching of the bottom cloth to the top cloth at specified intervals.  You specify the intervals, and you specify when and where you want to use them, but raising just one shaft of the patterned layer to be woven along with one pick of the plain weave layer wherever you want it. 

Here I have used plain weave for layer 1 on shafts 1 and 2, and an advancing threading over 6 shafts for my second layer in a ratio of 1:1.  When weaving this, I lift shaft 1 for my 1st pick, shaft 2 for my 3rd pick, and whatever weave structure I wish to use on the bottom layer for picks 2 and 4, remembering to lift shafts 1 and 2 out of the way.  When I want to join the two layers together, I simply select one of the shafts from 3 – 8 to be raised with either pick 1 or pick 3.  Those warp threads from the shrinking layer are then combined with the top layer (weaving with the top weft) and are stitched in place. 

You have total control over what sort of pattern you wish to weave into the top layer, and how frequently. 

The finishing treatment then does the magic.  If you are using wool as your patterning layer, and cotton as your plain weave layer, you will find that, depending on the amount of shrinkage you apply, and the properties of your yarn, you will get crinkles, bubbles, convolutions and collapse effects.  The looser the underlying pattern structure, the easier it is to full or shrink.  The more agitation you give it, the more it will tighten up and the more the top cloth (non-shrinking) will pucker. 

This is a really versatile weave, and it’s great fun to experiment with.  Try different ratios, different combinations of shrinking and non-shrinking yarns, different finishing treatments.  Even the different types of water that the fabric is washed in will have different effects because of the amount of agitation you will need. 

Have fun!