To underline and give more weight to ruby's post.
http://www.domsub.info/breastprimer.html
As far as how long you had the breasts bound, it would very well depend on how tightly the bonds were. If the were bound, making the breasts rose colored, rather than a very dark purple. The breasts of rose could be bound longer than purple of course.
As to the purpose of the scene, was it to make her call a safe word? If it was, I hope it was discussed.
As to when was the first time I had a submissive call a safe word. Was during a flogging scene, and didn't do a warm up. Was to teach the submissive the difference between a good flogging, and a poorly done one.
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ID