Rekindle the Spark
Open the Armor Details screen and add the maximum amount of Kindling to any piece of Sunlit armor. You can add Kindling under armor mods.
Fully rekindling a piece of Sunlit armor unlocks its glow, and allows you to imbue it with a Spark.
Sunlit armor with the maximum amount of Kindling added can be imbued with Sparks, which boost specific stats.
"Every fire needs some kindling for the spark." —Eva Levante