There are 2 ways to make electroplating of custom-made Christmas baubles.

Electroplating
Material: Tungsten Wire Melting Aluminum, Cost is much lower.
It is widely used for some regular color, example, red glass ornament balls, glass baubles gold, blue xmas ornament glass etc.

water plating
Material: silver nitrate. The cost is much higher than electroplating as it need more people work on it. It is mainly used for some glass Christmas light ornaments, such as glass Christmas ornaments pink, white Christmas tree ornaments.