Hi All,I'd ask that you not be unkind to the new fellow, and remind you that not all on this board are as familiar with some aspects of Medieval History as some of you might be.
It is a fair question in my estimation, considering that several readily available and digestable histories of the Hundred Years War mention the Black Prince as 'having black armour' - the key being to understanding that many perfectly good historians can be very ignorant regarding actual material culture of the time they are writing of, with the usual exception of very visible architechture left, or famous paintings. Material culture is not their specialty, and so they perpetuate myth alongside of good historical analysis.
As mentioned, it is not very likely the Prince of Wales Edward as the heir to the throne had armour of munition quality, left black from the forge. His train of sservants, extensive and documentable on campaign would readily be able to maintain a flawless white harness, or even gilt, or covered with luxury textiles that would mark him out as being of his 'station' in life.
Unlike our own modern age, where we consider elegant items not being designed with hard use in mind, conspicuous consumption was an absolute vital neccessity for the family of a monarch (as indeed amongst many lesser noble families) to 'maintain their station', and accounts exist showing items made for field use that most of us in the 21st century would be afraid to put to such use for fear of ruining - wearing a common or cheap armour would take away from a person of his stations prestige as much as wearing and using exceptional pieces would enhance it.
Very likely, his appelation came from his "Shield of Peace" as has been mentioned - or just as likely his vile temper, which was most famously displayed in his last campaign, as well as his office of governor of Aquitaine.
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Bob R.