CARDBOARD BONING
Concerning mid 1500 Florentine fashion and the eventual boning of bodices:
The bodice of the 1540's, despite being already longer and stiff, continued to be ample in form and with shoulders set well to the sides. Over the following decade, the profile tended to become more slender, not only because of the lowering of the waistline but also because of a closer and more tight-fitting cut, which left no room for the bust.
The padding of the garment was obtained by an internal layering of the fabrics, the doppia, made up of a felt and two types of cloth, one stiffened and one finer, San Gallo cloth or bottana, and for girls even cotton bambagino or bombast.
Cardboard was also used, a typically Spanish system, which appears to have become habitual at the Florentine court from the end of the 1650's*. Usually this thick padding was covered with silk or even with taffeta of the same colour as the petticoat, and care was taken to choose the same or similar colours even for the fabrics of the inner padding.
(Moda a Firenze, page 84 and 85)
So... cardboard boning... or stiffening... how? "A typically Spanish system" doesn't tell me too much, I get the feeling that the authors of "Moda a Firenze" aren't quite sure either. They quote the Guardaroba Medicea, which describes it as such, but what does it really mean?
*Moda a Firenze writes 1650's. Can it be they mean 1550's?