Glass Masking

Start with a base colour (black) and put on a set of contrast dots (white)

This is what it looks like on a bead

And melted in:

Add a further set of base colour (black) in between the white dots.

I’m illustrating with Grey so you know what I have added in this step

This is what it looks like on a bead

Repeat this with dots in between each of the white dots

I’m illustrating with Grey so you know what I have added in this step

You should have something that looks like this (but on a round bead)

And on an actual bead melted in:

Add a white dot (using a stringer) on top of each of the black dots

Add a black dot (using a stringer) on top of each of the white dots

Add a black dot (using a stringer) on top of each of the original larger white dots

Add a white dot (using a stringer) on top of each of the central black dots

Add a small black dot (using a stringer) between each of the original large white dots

Stop, when you feel you have done enough

Anyway, hopefully this shows the principle. Now you just have to accomplish this on a round bead.