Gold fill (also known as gold-filled) items are composed of a solid layer of gold that has been mechanically bonded to a base metal. There are two main differences between gold fill and gold plated materials: firstly, gold fill is mechanically bonded, meaning it uses high pressure to adhere the gold to the base metal, whereas gold plated items are made using electroplating; and secondly, gold fill items have 50 to 100,000 times more gold in them by weight, as there is no standardization for the amount of gold to be used in gold plating. For these reasons, gold fill lasts much longer than gold plated materials; gold fill items can last 5 to 30 years before wearing through.
Gold fill pieces have the same appearance as 14 karat (14k) gold. In some cases, the base metal (such as brass) can tarnish, so it is possible for gold fill to have slight changes in color over time as well. In order for an item to be considered gold fill, a minimum of 5% of the total weight of the item must be 12k or higher. If the karat of gold is lower than 12k, the total weight of gold must be 10%.
Due to the relatively high amount of gold in gold fill product, it is an affordable alternative to pure gold. Those people who have metal allergies, and can typically only wear gold, can generally also wear gold fill safely and comfortably. Moreover, pure (24k) gold is not practical in many applications (such as wire and fine chain), as it is very soft and easy to break.
Rose gold fill is exactly the same as gold fill, except that rose gold is used. The only difference between (yellow) gold and rose gold is that rose gold is a gold-copper alloy, generally with 25% copper. the more copper, the more red the rose gold becomes. Because it is an alloy, there is technically no such thing as “pure rose gold”.