Back in the day, people used nickel to give white gold its shiny white metal look. However, many people (myself included!) are allergic to nickel and most quality jewelers won't use nickel anymore. Likewise, Gardens of the Sun does not use any nickel in any of our jewelry products. That said, we import our solder material from the UK and it may contain the slightest trace amounts of nickel. Unfortunately, we can't control everything.
Nowadays, many jewelers use palladium in their white gold, which gives it a grey tone and less of a warm yellow hue. When using traditional artisanal smithing methods, it can be challenging to get our temperatures high enough to properly melt the palladium.
When palladium isn't melted properly, it can affect the quality of the finished jewelry. That's why at Gardens of the Sun, we use silver and zinc in our white gold, rather than palladium.