I recently purchased a kagayaki 240mm Damascus gyuto from olpappy as a gift for my boss. Received it today and gave it the full spa treatment. First I buffed the patina off with wet dry sandpaper from 600 - 1500 until it looked shiny like a new shun. Ran hot water over it to heat up the blade and washed it off with rubbing alcohol and dried it off. Now poured the etching fluid directly on the blade one minute per side then neutralized with water. Repeated 3 times until desired results. Dried off the knife and wiped off the excess black stuff. Buffed with micro mesh pads, sharpened the blade and buffed the handle with mineral oil. Here are the results.