Hey John, learning to etch your blades is a real turning point in the whole process. Once you see the possibilities available with the etching process you'll be amazed at what you can do for your blades overall appearance. I etch all of my blades now because it's a very important part of my process. It doesn't just show off the quench line, it also tells on you if you messed up in your heat treating efforts.
I don't know how much more I can add to help you here. All these guys have just about said it all. That thread by Terry Primos is excellent! But, I certainly want to encourage you to do some experimenting with the etching process to find what works for you. You may have seen some of my comments in previous threads about my methods, but I'll go over it again here and try and answer some of your questions just from my perspective. The thing to remember is there's more than one way to skin a cat or etch a blade. Experiment! Don't be afraid to try new things.
Remember, this is just how I do it and is only to help you find your own way.
You asked:
1. grit to which you finish before etching
- I usually just take my blades to a 360 grit finish. The thing to remember is that the finer the finish, the finer the grainy texture you'll end up with. I like a more pebbled texture on my blades so that's what I shoot for with the 360 grit. Play around with a junk piece of knife steel that you've done a full heat treat on and you can learn alot.
2. how you prepare for etch
- After I get the blade ground and hand sanded to 360 I just wipe it down real good in acetone and hang it in my acid tank for a few minutes. Sometimes I'll just dip it for a few seconds to see if I need to go back to the heat treat process. For those times when I 'miss' my quench. Don't overlook this step either. It'll save you some time in your final finish stage.
3. etchant used, and time and temperature of etch
- I use 1 part water with 3 parts ferric chloride. The warmer the acid mixture the quicker the etch. So, it really depends on how much or a hurry you're in. The low side temp or minimum is about 70 degrees though. Much lower than this and you'll wait a good while for results. At room temp, I usually do the first etch for anywhere from 5 to 10 minutes, checking frequently 'just in case'.
After the first I clean the blade with a stiff bristle brush and baking soda and warm water and soap. I have a good look at it to see what it needs. Usually, I'll hit it with some 1,000 grit wet or dry sandpaper to enhance the highlights and slow down the pebbeled texture on the surface. You will usually enhance any wood grain pattern by doing this before proceeding. Then clean the blade again with acetone and put it back in the tank for a few more minutes. Clean it again and do your final hand polishing.
4. how you finish after etching
- I like to go to a 2,000 grit wet or dry sandpaper at this point. But I don't use water during this final phase. I just let the sandpaper load up and it actually shines the blade up perfectly. A side note here. If you want to 'set' the dark oxides in the blade that remain after the final etch now is the time to do it. I just mix up a pan full of water with baking soda in it. About a tablespoon per quart of water. Boil the blade for about 10 minutes and this will set the oxides much like a powder coat. At least that's been my experience. This also provides a fair amount of corrosion prevention too. The oxides will hold any oil you put on the blade afterward.
5. anything that comes to mind
- Always neutralize the acid etchant in some way each time you take the blade out of the etch tank. If you lay it down absentmindedly (like I've been known to do) it will make a mess of the blade. The oxides will turn to rust and break your knifemaking heart
Also, after etching, I noticed a wood grain type pattern along my transition zone. Any ideas?
- Make this work for you. You can really get some interesting patterns with certain steels. Have fun!
