Step 1.

Take a square sheet, lay it flat on the table, with the bottom edge horizontal.

additional information

  • If it is two-toned, place the colored side facing the ceiling.
  • The corners of the square are: top left, top right, bottom right, and bottom left.

Step 2.

Form a valley fold, vertical, by bringing the right edge to the left edge. Crease well, then unfold.

Step 3.

Form a valley fold, horizontal, by bringing the bottom edge to the top edge. Crease well, then unfold.

additional information

  • We have just marked the medians of the initial square.

Step 4.

Flip the folding from right to left, then place it in a diamond position.

additional information

  • The corners of the square are now: top, right, bottom, and left.

Step 5.

Make a vertical valley fold by bringing the right point to the left point. Crease well, then unfold.

Step 6.

Make a horizontal valley fold by bringing the bottom point to the top point. Crease well, then unfold.

additional information

  • We have just marked the diagonals of the original square.
  • On the paper, you can feel that:
  • The medians are mountain folds (the fold of the medians forms a ridge)
  • The diagonals are valley folds (the fold of the diagonals forms a trough)

Step 7.

Bring the top point to the bottom point, using the existing horizontal valley fold.

additional information

  • You get 2 superimposed triangular flaps, connected by a horizontal hinge edge at the top.
  • On the front and back faces of the shape, two valley folds connect the middle of the hinge edge to the middles of the right and left sides of the triangular flaps.

Step 8.

Hold the fold between the thumbs and index fingers of both hands, so that the thumbs, in front, come into contact with the middle of the front valley folds, and the index fingers, behind, come into contact with the middle of the back valley folds.

additional information

  • The fingers of the right hand are just to the right of the right valley folds.
  • The fingers of the left hand are just to the left of the left valley folds.
  • The shape is no longer on the table.
  • It is held vertically in front of us, the hinge edge horizontal, and the third point of the triangle pointing toward the table.

Step 9.

Shape it into volume. To do this, push both hands downward symmetrically until the thumbs and index fingers meet.

additional information

  • The shape has opened, and we get 4 triangular flaps of double thickness.
  • One to the left, in the left hand.
  • One to the right, in the right hand.
  • One free toward the front.
  • And one free toward the back.

Step 10.

Tilt the front flap to the left, and hold it against the left flap.

Step 11.

Tilt the back flap to the right, and hold it against the right flap.

Step 12.

Place the folding flat on the table; the base of the water bomb is ready.

additional information

  • We have a triangular shape with:
  • A closed tip at the top,
  • And 4 double-layer triangular flaps, open at the bottom.
  • We feel a vertical valley fold in the middle of the shape, running from the closed tip to the middle of the lower edge. This is the vertical axis of symmetry.
  • The 4 flaps are connected to each other by the closed tip at the top and the vertical axis of symmetry.
  • There is a front left flap, a rear left flap, a front right flap, and a rear right flap.