Even though they have an open hole, they tend to inflate rather than [deflate] when bounced up by hands. According to Ichiro Fukumori of the Jet Propulsion Laboratory, 'Despite the open hole visible in the silver patch, the kamifūsen stays inflated when bounced on the palm of one’s hand. Moreover, repeated bouncing causes a deflated kamifūsen to swell by itself to its fully inflated condition. The elastic rebound of the balloon paper is not enough to explain the full inflation; a batted kamifūsen actually sucks in air from the atmosphere.'
The 10:1* paradox

The tile tool

A curved mirror is the key component to any reflecting telescope. It’s precise curvature allows one to see into the depths of space. The tool used to shape the glass mirror is an assemblage of randomly shaped shards of broken tile glued to a disc typically made of sealed plaster or concrete. The ceramic fragment disc (with abrasive applied to it), will create a sagitta, a perfectly concave depression, when brought in contact with the glass blank over time.

The secret to producing a perfectly shaped mirror lies in randomness. The size and spacing of the ceramic fragments when assembling the tool, and the stroke numbers and rotation of both the tool and glass when grinding, will yield the best results.

*According to industry standard, tools used in the manufacturing process should be ten times as precise as the tool being produced.
structural anomaly