I will evaluate the relative mechanical strengths of the two windows I've created so far by dropping a 28.15g steel ball onto them from increasing heights and studying the results. After each drop I will inspect the window for damage. If I find any, I will circle it with a permanent marker to ensure I don't confuse earlier damage with later drops.

For the first window I filled in the paperwork by watching the video. I was more diligent at accurately filling in the results for window 2 during the tests.

Final adjusted results.

The windows after the testing.

There was not a huge difference in measured toughness of these two windows. The error bars on this experiment are quite wide, but I'd lean towards maybe window 2 being tougher. Possible reasons:

• The potassium treatment weakened window 1
• The higher number of temperature cycles weakened window 1,
• Different sources of glass,
• Window 2 is thicker (approx. 14.5mm vs 17mm)

The other interesting thing is the gross failure mode. Both windows snapped pretty cleanly straight down. Neither cracked along the laminations of their composite glass sheets. This indicates good amalgamation of the layers into a solid mass.