temper line

[rasp181]

I just completed my first forged knife made from a piece of hay rake tine and I feel it turned out very good. I then normalized and annealed the blade to do some final touch up before heat treat. After the knife came out of heat treat I got a great temper line which I want to preserve. I searched the threads but didn't find the advice I'm looking for. I plan to hand sand to 400 grit. Do I soak in vinegar first or after final sanding? If after to bring out the temper line that would be fine because I favor the patina from vinegar etch anyway.

[Ray Rogers]

Developing that line can be done quite a few different ways, and different methods may work better on different steels. The one thing they all have in common is that they are done after the steel is finished.

Developing the temper line will probably take several dips into the etchant followed by additional sanding or buffing or steel wool depending on which you prefer and which works best on that steel.....

[GHEzell]

I suggest sanding, then etching, then a paste polish for the final finish, but as Ray said there's as many ways to do it as there are makers who etch.
A few tips: Get the blade clean before etching with a good solvent. No fingerprints allowed..
The higher grit the blade was finished to before the etch, the better the etch will look. 400 grit is good, but 600 is better. 2000 is overkill.
The stronger the etchant, the faster and deeper the etch, and the more likely the stuff is to hurt you if you touch it. Ventilate and protect your hands.

The reason I use for the paste instead of sanding for the final finish is that the sanding can blur the detail of the crystaline structures in the steel that are brought out in the etch, while the paste accents the structures.