Silk burns easily.
The Silk Shirt is the third-weakest clothes, providing +7 Defense, reducing Thunder damage by 50%, and teaching Cure and Thunder. It can be bought for 400 gil at Dali, Treno (before going to the Outer Continent), Lindblum (after the invasion of Burmecia but before going to the Outer Continent), and the Black Mage Village (before entering the Shimmering Island), found in Alexandria from Brahne (beginning of the game) by impressing 80–99 nobles during the play, or stolen from Steiner or Black Waltz 1.
The Silken Shirt is a low-ranked mystic armor that provides +6 Defense and +2 Magick. It can be bought for 300 gil at Rabanastre, Nalbina Fortress, and Bhujerba, and requires 20 LP and the Mystic Arm 2 license to equip.
In the Zodiac versions, it now provides 6 Defense, +8 MP, +2 Magick Power, and requires the Mystic Armor 2 license for 15 LP. It can be bought in Rabanastre and Barheim Passage for 300 gil, found as a treasure in Garamsythe Waterway (No. 10 Channel (Flooded)), Nalbina Dungeons (The Black Watch) or in Trial Mode Stage 5 (with Diamond Armlet), or stolen from Ghost (3% chance). It can be equipped by the White Mage, Red Battlemage, Black Mage, and Bushi.