Adjusting Particle Properties Using Curves

With the ParticleCurve, you can apply a curve to particle properties (such as size or mass) to change them over time.

1.   Connect the node to your particle node stream.
2.   Adjust the curves in the ParticleCurve properties panel. The x axis represents the lifetime of the particles.

r - adjust the curve for the red channel.

g - adjust the curve for the green channel.

b - adjust the curve for the blue channel.

a - adjust the curve for the alpha channel.

size - adjust the curve for the size of the particles.

mass - adjust the curve for the mass of the particles.

A size curve modifying the particles to grow
in size toward the end of their lifetime.

Note:  To use the ParticleCurve with RGBA values, you need to apply a BlendMat node to the texture, and set the surface blend knob to modulate. See BlendMat for more information.
This is because the ParticleCurve node edits the particle vertex color, which only works when there is no particle input. By adding a texture or shape as the particle input, this overrides the particle vertex color and uses the particle input instead. The modulate value in the BlendMat node multiples the particle's texture by the vertex color, allowing them to work together.

3.   If you want, you can adjust the curve for your particles’ alpha channel so that each particle fades to invisibility toward the end of its lifetime.