It’s when you wear a new corset quite loosely about 2-4 hours per day for about 1 month.
This helps to acclimate your body to your corset & vice versa; or get them used to each other.
In other words, you are “breaking in” your corset.
As the month progresses, you tighten up your corset slowly everyday.
Corset seasoning ensures that the corset won’t break easily, and it gives the corset enough time to understand the curves of your body.
There are different methods or approaches to corset seasoning, and not one way is “right”.
But Lucy Corsetry mentions the 2-2-2 method.
For 2 weeks, wear your corset with a 2 inch reduction, for 2 hours.
Good corset seasoning will ensure that the corset doesn’t break, and that you dont hurt yourself.
You wouldn’t try to squat 100lbs on your very first day at the gym, or attempt to run a marathon without training weeks or months beforehand.
Likewise, with your new corset, you need to give it enough time before you really start tugging on those laces.