You really should leave the craze because removing it often devalues the piece. But, if you are intent on cleaning it up, try the least harmful product that removes soot, Krud Kutter, straight. You can find it on the cleaning aisle at Lowes. I collect antique china and have many of the platters hanging on a wall that were covered in soot after the fire. After contacting several experts about removing the soot, I found most recommended this product. It worked not only on the antique china, but also on drywall, painted surfaces (like crown molding, baseboards and wainscoting), it is biodegradable, fume free and non-toxic, too.

idk, but too bad about the fire!