Reticello

A pattern created by two spirals opposing on the same plane.

Traditionally, with soft glass, glass canes were heated, twisted in one direction, and blown into the form of a cup. The cup was set into an oven. Then, a second cup was made in the same fashion, however the glass cane was twisted in the opposite direction. The second cup wass blown into the inside of the first cup. As the two cups come together, the grooves between the cane rods are sealed, causing air bubbles to lock into the crisscrossed pattern. The connected cups were then blown and formed into the final shape.

The same effect can be achieved in boro without the internal air trap. Stripe a tube, then spiral. add the same number of stripes, then spiral the reverse direction half as far as the first time.