This page was created from Joel's Interactive Guide to Straight Razor Shaving from this thread.
What does a slurry stone do, and what are they?
A slurry stone is a stone with which you rub on your hone to create "slurry" or a milky liquid on the top of your hone, which helps some hones cut more effectively. These stones are typically referred to as "slurry stones" for European stones, and as "Nagura Stones" for Japanese stones, and they are actually different. A slurry stone is a stone made from the same material of the hone, in the same grit, and will look identical to the hone--basically a small little block of hone. By rubbing the slurry stone on the hone--the two identical materials abrade one another and create a milky abrasive liquid, and lift the cutting agents from the hone and the slurry stone. On the other hand, Japanese Nagura stones are actually a different grit, and for that matter a different material all together. Nagura stones are typically white (but come in varying colors and grades) and their purpose is to usually make the hone cut finer/create a finer polish on the edge, however in some rare instances Nagura stones will make the hone more abrasive.
How do you use a slurry stone?
This is the easy part. Merely rub the slurry stone back and forth across your wet hone until you see a slurry!