How does the breast plate on the suit of armor & Pearl help define the symbol of the Scarlet letter A

In chapter seven Pearl points out Hester’s distorted reflection in the breastplate of a suit of armor so that Hester appears hidden behind the scarlet letter.The Scarlet letter thus becomes Hester's identity. It is as if her "sin" has become, through the breastplate, the embodyment of Hester and Pearl a living symbol of it.