Aurelia Kresling Corona 01

A crown. One long strip of twenty-four triangles, cut from a single flat sheet, folded along its own lines and rolled into a short tube that sits on your head. It is about 190 mm across and 95 mm tall. Nothing is glued and there are no screws — a tab pushes into a slot and holds.

It packs flat. Press it and it collapses into a ring you could put in a bag; let it go and it stands back up. There is a slit at the back that adjusts from 14 to 19 cm, which is how one crown fits different heads.

The card calls it an Aurelia Kresling Corona, which is three hard words for a folded paper crown. Corona is Latin for crown. Kresling is the name of the fold pattern — more on that below, because it is the good part. Aurelia is just what this one is called.

The drawing names two materials. The plain one is 220 gsm paper or board, which is thick card, and it is what most people will actually use. The other is Tyvek, a sheet of spun plastic — the stuff tough express envelopes are made from. It is slightly see-through and very hard to tear.

On the Tyvek version the tips get a strip of copper a tenth of a millimetre thick. Copper left in damp air turns a soft green over months. That green is the same sage as the fold lines on the sheet, and it is deliberate.

SIZE

about 190 mm across · 95 mm tall

PANELS

24 triangles in one continuous strip

SYMMETRY

12-fold — the pattern repeats twelve times round

TWIST

22.5° between the bottom rim and the top rim

OPENS TO

38° from flat — the drawing’s figure, never measured

HEAD FIT

slit at the back, adjustable 14–19 cm

SHEET

A2 · 594 × 420 mm · drawn 1:1 in millimetres

MATERIAL

220 gsm board — or 0.3 mm Tyvek with 0.1 mm copper tips

AREA

0.22 square metres of material

LOCK

T-lock · 12.0 mm tab into a 12.4 mm slot

HARDWARE

3 mm copper eyelets, optional · no glue

LICENCE

MIT

This is the good part, and it is the reason this is a machine rather than a paper hat.

That is what a Kresling pattern is: a named, published fold pattern for a cylinder, so a tube collapses the same way every time instead of a new way each time. Twenty-four triangles, twelve of them pointing up and twelve pointing down, wrapped into a tube.

Push the crown down and the top rim rotates. Let it go and it rotates back. Here the turn is 22.5 degrees, and every panel round the tower shares it equally, which is what 12-fold symmetry means: the same shape, twelve times, every 30 degrees.

It is also bistable, which means it has two resting positions and nothing in between: flat, and open. Push it past the middle and it finishes the move on its own. It snaps, and you can hear it.

The drawing also calls the crown auxetic. That word means a thing gets wider when you pull it. Stretch a rubber band and it goes narrow; an auxetic material goes wide instead, and almost nothing does. Its own numbers say this crown does the ordinary thing. That disagreement is in the last section, unresolved.

AN EVENING. A KNIFE, A RULER AND ONE BIG SHEET.

The full-size sheet is not on this page yet. The back of the card points here for it. Until it lands, what follows is what the sheet says and what to check when you have it — and the wishing well at the bottom is how you ask for it.

1. Print the sheet at true scale

   The sheet is drawn 1:1 in millimetres on A2, 594 × 420 mm. Print it at 100% / “Actual size”. No home printer takes A2, so tile it across A4 or Letter and trim the overlap — the tiles line up because the drawing is dimensioned rather than fitted.

   “Fit to page” is the one setting that ruins this. It shrinks the sheet a few percent, which you cannot see on paper and cannot miss in the lock: at 97% a 12.0 mm tab is 11.6 mm, and the crown never closes.

2. Check the ruler before you cut anything

   There is a 10 cm ruler printed on the sheet for exactly this moment. Put a real ruler on it. It must measure 100 mm. If it does not, the print scale is wrong — change the setting and print again. Thirty seconds against a whole sheet and an evening.

3. Cut every solid navy line through

   Solid navy is a cut. Take the blade all the way through. The twenty-four triangles are one continuous strip and they must stay joined — you are cutting the zigzag along the top and bottom edges, not cutting the triangles apart from each other.

   Count the shapes. Do not trust the printed labels. They skip four numbers, repeat two others, and there are fewer labels than the drawing says there are panels. Cut what is drawn. The last section has the details.

4. Score the living hinges — two cuts, half depth

   A living hinge is a fold that is also the joint: no pin, no pivot, the material just bends in the same place every time. This sheet makes them with two parallel kiss-cuts — cuts that go only halfway through — set 0.3 mm apart. Never go through.

   This is card 004’s hinge, unchanged. If you built Carpal Bloom, you have already done this and your hand knows the pressure.

5. Fold every dashed sage line flat, then open it again

   Dashed sage is a fold, not a cut. Fold each one a full 180° so the two sides touch, then open it. They alternate, one way then the other, all along the strip. That alternation is the twist — get one backwards and the tower will not turn.

6. Roll it into a ring and lock the tab

   Bring the two ends of the strip together and push the 12.0 mm tab into the 12.4 mm slot. Use your fingers, not a mallet. If it will not seat, a fold near the end is not creased all the way.

   A 12.0 mm tab in a 12.4 mm slot leaves 0.4 mm, and that gap is the whole fit: tight enough to hold on its own, loose enough to push home by hand. It is cards 001 and 002’s lock, unchanged.

7. Fit it to your head

   The slit at the back slides open from 14 to 19 cm. Widen it, put the crown on, and let it close until it sits without gripping. If you have the 3 mm copper eyelets, set them now — they are optional and stop the holes tearing with use.

8. Press it flat, let it go, and tell this page

   This is the moment the whole design is about. Push it down until it snaps shut, then release it and watch the top rim turn. Time how long it holds up. Count how many times you can do it before a hinge gives.

   Whatever happens, put it in the wishing well at the bottom of this page. Nobody has these numbers. You would be the first person to have any of them.

This is card 005, and most of it was paid for by the cards before it. That is the point of the book: a later card should cost less to build than an earlier one, because it borrows joints that already work instead of inventing new ones.

FOUR MARKS, AND THEY MEAN DIFFERENT THINGS

The swatches are drawn on white because that is where you will meet them — on your own printout, in the sheet’s own navy, sage and copper.

Nobody has measured any of this. Here is exactly where that matters, in order of how much it would change what you get.

None of this makes the design wrong. It makes it untested, which is a different thing, and the difference is worth a whole section on the page a stranger reads.

This card is MIT. Do what you like with it, including sell it, as long as the copyright line travels with it. Cards 001, 002 and 004 in this book are CC BY-NC, which forbids selling. This one is not, and that is not an oversight — its author set it to MIT and it was left the way they set it.

MIT also says there is no warranty of any kind. On a design nobody has built, read that line twice.

vc1|AURELIA-CORONA-005|Aurelia Kresling Corona 05|2026-08|MIT|vibe-cards

The chip carries that line in plaintext, next to the address. It needs no server and no network to say what this card is — so if this page ever dies, the card still knows.

This card’s address can never change, so anything new about it has to land here: corrections, a fold order that turned out better, a material that held up, a tab size that turned out to be wrong. Tap the card again in a month and there should be something on this page that is not on it today.

The first entry this page is waiting for is from whoever folds one.