You can get a very cheap ball mill by buying a National Geographic rock tumbler for kids, then using 4mm ceramic balls found on Amazon.com. Excellent for wet milling. I believe I am getting particle sizes less than 10 microns after 8 hours of milling. It runs in the corner of the kitchen, and it doesn't make too much noise. Four hours gives a fine grind, and overnight is very, very fine. The whole price is under €100 in Europe, and probably under $70 in the USA.

There's a lot of research lately about ancient people roasting yellow ochre to turn it red. That makes sense if there's no red ochre available, but my question is why would anyone do this when there's red ochre already available nearby? I have my own hypothesis, but I'd like to hear what others think or know about this.

I'm probably the only person in Washington state who doesn't drink coffee, but I've got two coffee-related household hacks I use when processing pigments: 1. After I've broken my pigments down to just the stage before grinding them, I throw them in one of those electric coffee bean grinders and finish them off in that. It actually works great, reducing softer materials to pigment size quickly, and helping reduce harder materials to a reasonable size for mulling. 2. To sift my pigments I use one of those non-disposable brass mesh coffee filters. The mesh is the perfect size for sifting material to pigment-grade size.