Changing just the render properties, how does one get rid of the ashes in this room. I've tried every setting I can think of.

Check off the 'interpolation' option, Photon Count to 25000, this version. The interpolation thing is the biggest (you can try for 50 or 75 first, if time/speed is an issue), but the higher the settings for photon and the smaller the samples, the better the image will be. But you gotto love your coffee (and garden) because rendertime will increase greatly. Good luck!

Ok. It appears afterall that the Interpolation setting works in the opposite of how Eovia describes. Leaving it unchecked should allow for faster renders with ashes left on models, while checking it off and selecting its percentage should determine how slow/precise you want it to render in order to not have ashes.

Of course not. No interpolation means full calculation. Once you check the box, larger parts of the GI and IL are going to be 'guessed by interpolation' by Carrara. The higher the number of the interpolation slider, the higher the precision, because more calculation will be done. Perfectly logical. Interpolation is a lower-quality and faster way of calculation (not unlike the jpg compression method that describes larger samples of information is) and you give up some quality for increased render speed. Not using any compression/dergrading is always better, but most of these are created to save time and/or space. --- But it seems every answer you get on your questions and remarks will bring you the conclusion that either Carrara or Eovia suck big time (and your brilliant mind has come up with far more superior solutions). If you want to spend your days shaking your head over the dumbness of the rest of the world, that's fine, but on me you do not make a very smart impression. Trying to find things out for yourself (make some test renders with different settings to compare them) is not that hard. That is called 'learning', that does not have to be taken care of by anyone else but yourself.

You cleared things up. JPG compression I understand. Your comparison to that is the best I've seen on what interpolation means/does for Carrara renders. Thank you.