The difference between white gold and yellow gold is the different metals that are mixed within the gold alloy.
These metals in combination with the pure gold “gives color” to the gold alloy.
For example, yellow gold alloy is usually mixed with copper and small amounts of silver.
There are quite a few different compounds of gold alloy and there is no one uniform compound that is used worldwide, apart for the branding of gold purity (karat).
For example, a yellow gold compound of 14 karat contains 52.5% gold, 4-28% copper and 14-28% silver, depending of where it was produced.
On the other hand, 18 karat gold alloy contains 75% gold and the ratio between copper and silver differs according to the manufacturer.
The alloy of the white gold is produced by mixing of gold with white metals as palladium, nickel and zinc.
The resulting alloy is whiter but still has a yellowish shade.
For this reason, all jewelry produced from white gold alloy are coated with radium with the goal of whitening the jewelry and make it shine.
Due to the fact that radium tends to pill off, there is a need to renew the coating every few years or maybe ever more frequently if the jewelry is being used daily and comes into contact with cleaning supplies, etc.
In both cases, both white gold and yellow gold, alloy that is branded by 14 karats is slightly stronger and more resilient.
Pure gold by it`s nature is very soft and therefore high gold concentration will affect the entire alloy.
14 karat or 18 karat gold?
The price difference between 14 karat alloy and 18 karat alloy of the same jewelry results from two main variables: the first one is the difference in gold concentration between the two alloys.
This difference produces a price gap due to the fact that pure gold is much more expensive than the other metals within the alloy.
The second variable and the less trivial one that most people are not aware of is the material`s density (specific gravity).
Since the density of 18 karat gold is higher than the density of 14 karat gold, more gold is required in order to produce a ring with a certain volume and size with 18 karat gold.
According to most cases the difference is about 20-25% with relation to the metals found within the alloy.
The practical meaning is that a certain 14 karat ring weighting 2 grams, will weight approximately 2.40 grams if made from 18 karat alloy.
So which karat should I choose?
While talking about white gold, there is no additional value in choosing 18 karats since all white gold jewelry (without any relation to their alloy purity) are coated with radium and look exactly the same.
In case of yellow gold, there is a significant difference in color – 18 karats gold is much more life-like and has more resembles to the color of pure gold.