Some comments upon the construction of the circles of the Rosettes

[davidjackson]

Is there any chance it was done with a bottle?

I don't think so. It would be different bottles, for a start, as the circles are different. IIRC, due to the imbalances caused in 15th century glassblowing, most glass containers of the time had circular or square feet that we attached to the bottom of the container.

There isn't an overlap on these circles. Instead, it seems that the circle peters out, as if the ink runs out. This would be consistent with a compass which is twisted around once quickly; if it were a bottle, the bottle would be fixed and you could do a better job, but the lines would probably be thicker.