So, in order for crystals to start forming, there has to be a nucleation site.

Once the nucleation sites are consumed the formation of new particles will cease.

There needs to be a provocative point called a nucleation site.

If I remember correctly, the smaller the nucleation sites the more energy it takes to create a bubble.

Dissolved gas can also provide nucleation sites when it comes out of solution and forms bubbles.

Gold particles then act as a nucleation site and silver is deposited onto the particle.

In addition you must prevent other things from providing nucleation sites.

The reason is entirely in the number of nucleation sites.

In general, the number of nucleation sites are increased by an increasing surface temperature.

This starting point is called a 'nucleation site' and it often comes in the form of an impurity.