I have a a particle and the emission start time is set to 42 but when the animation plays the particles are visible emit right from the start of the animation.
The problem is the particles are visible as soon as the render starts, but the particles are only supposed to be visible and start emitting at frame 42. I’m not sure if it is a material issue or a particle issue. I’ve tried making the material transparent but then the particles are transparent too. I hope there’s a simple way to fix this.
Blender Wiki - Particles
The cache is cleared automatically on changes - but not on all changes, so it may be necessary to free it manually e.g. if you change a force field. If it is impossible to write in the subdirectory there will be no caching.
The cache can be freed per physics system with a button in the panels, or with the CtrlB shortcut key to free it for all selected objects.
If the file path to the cache is longer than what is possible with your operating system (more than 250 characters for example), strange things might happen.