I'm working on an animation where a match lights itself on fire and I'm trying to figure out if there's a way to animate the swapping of materials so it can go from a clean tip to a burnt tip. Originally I was just going to render up to where i wanted the material to swap, manually swap it, and restart the render from that point, but it seems like there should be a more automated way. I couldn't find any information about whether or not this is even specifically possible, but if anyone can help let me know.
you can use a multi-layer material to house your two materials then just animate the opacity change between them to change it.
you could even put a ramp on that opacity to get more control over it
Another way would be to have two matches, and key the visibility.