Brit Knits: Amazing Harry Potter Illusion Shawl

When Anglophilia and knitting meet, amazing things can happen. Steven Plummer and Pat Ashforth illustrate this point perfectly. They specialize in illusion knitting, one of the most amazing things I’ve ever seen. I have been knitting for over ten years now and I am no where near the skill set needed to work up one of these beautiful works of art. So with out further ado, enjoy.


Steven Plummer and Pat Ashforth explain their process:

We asked First of all a bit about us…

My wife and I wrote our first book together long before we were married and consequently retain our different surnames, she is Pat Ashforth and I am Steve Plummer. Together we make up the Woolly Thoughts design team. Pat is trained in maths and English and I am trained in maths and art. We have both been mathematics teachers of 11 to 16 year olds and met, over twenty years ago, in a school in Luton, England, where the student intake was 97% Asian with English being very much a second language. We are both geometers rather than algebraists and have a keen interest in shapes and how they fit together and in answering mathematical questions through geometric means. Pat was also a prolific knitter but did not follow traditional knitting patterns and together we developed ideas about fitting together mathematically correct  garter stitch shapes to form garments.

When I left the school, to become a Head of Mathematics, we decided we had enough ideas to put them together in our first book Woolly Thoughts and I taught myself to knit, from Pat’s written instructions, so that I had enough understanding of the craft to illustrate those written instructions. The ideas in this book were noted by the Brown Sheep yarn company in America who asked us to create an afghan for them. In creating this afghan we found that the larger scale we were working to allowed us to put far more mathematical ideas into a wall hanging than we had previously been able to put into a garment. We have rarely, since that time, again looked at producing knitted garments and have become best known for our design and production of large scale knitted or crocheted mathematical wall hangings initially created for use within our mathematics classrooms to engender discussion, particularly with children who had poor English skills. We even have a number of our pieces of work in The Science Museum in London as part of their mathematical collection.

Now, many years on, we are both retired from teaching mathematics but retain our love of the subject and our “what happens if…”, unconventional approach to teaching it.

Since we retired from teaching we spend much of our time seeking mathematical ideas to develop as designs for wall hangings or artefacts and continuing to question our design process. Part of this questioning led Pat to look at shadow knitting, or illusion knitting, and we, very quickly, formed the opinion that explanations and charting processes for this technique forced the position where only very basic, almost primitive, images could be created. Our inquisitive nature, love of designing and mathematical grasp of charting and visualisation in three dimensions along with our abhorrence of badly written or planned patterns led us to experiment with and develop the charting process.

Illusion knitting relies on the fact that ridges of garter stitch and ridges of stocking stitch in knitting have different properties. Garter stitch ridges stand forward further than stocking stitch and this allows you to create a design that changes its appearance dependent on the angle of viewing. In illusion knitting two colours of yarn are used to create alternate ridges of knitting, a dark coloured ridge followed by a light coloured ridge. Areas of dark or light can be brought into the foreground, when the piece is viewed at an angle, by using garter stitch for that particular part of a ridge and stocking stitch for that portion of the preceding ridge. When the piece is viewed from directly in front only stripes of colour should be seen. Our maths and my maths/art background allowed us to develop the charting process for this technique to the point where I can create far more complex images than have previously been possible, incorporating not just areas of dark and light but also areas of various levels of intermediate shading.

To create a complex illusion knit I, first of all, decide on an image to use. To have a certain “Wow” factor this image needs to be recognisable by those who view the illusion and so faces like Harry Potter’s are wonderful to use. The smallest detail that I want to show within this image must be, at least, one stitch across and this smallest detail therefore determines the scale of the completed piece. After determining the scale I put a square grid over the image, each square on the grid representing one stitch and each row of squares representing one row of knitting. I now “look through” the grid and decide on areas of dark or light that I need to see and colour in squares on the grid in the appropriate dark or light colour. When I have completed this process all coloured in squares are knit stitches and all squares that are not coloured are purled stitches when I come to knitting the piece. I do use a computer to draw these charts on but it is very important to note that it is not the computer that draws the charts. It would be possible to draw the charts by hand using tracing paper but a computer drawing package that allows different layers to be created and then turned off or on is far more convenient for this process.

The charting process takes perseverance, time and an amount of three dimensional awareness. Each chart takes me, on average, about 100 hours to produce and I will test knit the piece as I go, refining the chart as necessary to ensure that the completed piece does exactly what I want it to do. The hand knitting itself will again take me, on average, about another 100 hours but this is partly because I knit rather slowly.

Further insights into and photographs of our mathematical work can be found by following this link to our Woolly Thoughts web-site…

…and on our illusion knitting here.

The patterns for all of our pieces can be found by accessing the order form from the Woolly Thoughts web-site.


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