In jewelry, pure 24 carat gold or not used for being too soft. Instead it is mixed with other metals to obtain a stronger and more durable alloy, depending on the metal and the proportion with which to mix, one color or another is obtained. It is therefore the proportion of pure gold to be used to define the law and with metal mixing that defines the final color of the alloy.
75% gold and 25% other metals would result in a gold at a grade of 18 carats that is common in Spain, and if the proportion of gold was lower gold would result in a lower grade, for example 14 or 9 carats, much more common in other countries.
As for color, an alloy of 18 carat gold is composed of 750 parts per thousand pure gold while the remaining 250 thousandths may be:
- Copper (red)
- Copper (70%) and silver (30%) (pink)
- Copper (50%) and silver (50%) (YELLOW)
- Silver (greenish)
- Silver (14%), copper (14%) and palladium (72%) (WHITE) *
* It is important to note that the percentage of palladium presented here is the one we usually use in our workshops and is not usually the common market, being generally lower or even non-existent percentage. A palladium composition ensures high durability of the white tone, however, tends to yellow in other alloys that lack the usual when this rhodium applied to all white gold alloy disappears by wear of use the piece, hence its importance.