It is not every day your origami design is folded 10,000 times by others, but that happened to my angel this summer.
The Ripon Cathedral runs the campaign A Wing and a Prayer with an installation of 10,000 angels praying under the COVID-19 pandemic. 100 volunteers and 300 children aged 3-90 years helped realise the dream, and the campaign helps funding the Yorkshire Air Ambulance.
The installation is open through 31. January 2021 and the Ripon Cathedral in Northern England, 40 km northwest of York, is certainly worth a visit. Travelling is currently difficult, but you may view videos and images from the installation.
This photo by Russel Wood (©️ 2020) shows the church room where the angels are draped in waves 15 meter above the floor.
(The article continues below the image)
Thoughts behind the angel
In 2008 I was asked by Pecha Cucha Copenhagen if I would give a Christmas themed talk, preferably including the audience actively.
Pecha Cucha is a format where you have 20 x 20 seconds to present a topic.
So I designed this angel. The rigid design criteria: 20 steps, 7 minutes, a large audience with little prior experience in origami; led to a simple model with a pure and clean design: Wings, dress, and head with a halo.
I created instructions as a slide show with a front page and 20 pages each with one step. Each page had a title, a gif continuously displaying how to perform the fold, a diagram step, and a drawing of the result of the step.
And thus on the 3. of December 2008 I faced 400 people in Stærekassen, one of the scenes of the Danish Royal Theatre.
The original model had a real neck which looked better from the front. Later I made a cleaner version where the neck was marked only, or even left out (see pattern and instructions below). The Ripon Cathedral’s instructions also omits the neck, but folds the flaps on the back orthogonally instead of slanted, which is a bit simpler but changes the halo shape making it more squarish.
Fold an origami model and unfold, then the crease lines emerge. Together they form the Crease Pattern or just CP.
Most lines will be part of the final model as 180 degree valley or mountain folds.
Some, like the vertical line in the back, has no function but is an artefact of the folding sequence.
And some, like those in the neck, have a visual function but are not flat.
Finally, the curves like those of the wings. They are not part of the crease pattern even if i.a. Andrew Hudson has suggested how curvatures might be diagrammed.
The two colour theorem
The two colour theorem states that the crease pattern of flat-foldable models can be coloured using at most two colours.
A consequence of the theorem is that if you re-fold a coloured crease pattern, one colour ends up on one side of the folded piece, and the other colour on the other side.
That is a variation of the four colour theorem that states that maps of contiguous countries can be coloured using at most 4 colours. The flat-foldability condition applied to crease patterns ensures that 2 colours suffice.
The neckline of the angel is not really a fold, but a marking. If you avoid that and the vertical line in the back, then the angel has a flat-foldable crease pattern.
That is illustrated in the crease patterns below where the areas have been coloured rather than the crease lines themselves.
Print them, cut out the two squares, and fold them.
One pattern provides an angel white in the front and black on the back, and the other pattern provides the reverse colouring.
You might consider the theological implications of black and white angels.