From my humble experience, a blade of good high contrast pattern will show up fast and clear, with whatever acid used for etching. When I travel I use Coca Cola from the hotel room fridge to test the blades I purchased and with good wootz it works well. Also, with good wootz the pattern will show even if the blade is not highly polished. It is a bit more difficult to bring out the pattern of wootz of lesser contrast like Indian Crystalline or Sham wootz, or some laminated blades.
After many years of trial and many errors I use a mixture of Iron Chloride with Nitric Acid. Both very diluted 3-5 %. The Nitric acid is added to remove the Yellow / Brown tint sometimes appears on the blade with Iron Chloride. Let me also suggest to use room temperature acid on room temperature steel. Heating will only accelerate the etching and might be that it works too fast and mask the pattern. Direct sun light will help to bring the pattern faster.
The following basic rules should be kept:
- Clean polished blades, without any traces of oil or grease.
- Diluted acids
- A lot of patience.
Good luck
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