Crazy enough to work?

[cbsmith111]

I know you're busy, so don't feel pressed to reply to this, but I did a little experimenting this weekend with a knife I made that didn't really turn out so I wasn't worried about ruining it.

The knife was made from A2 and had been hand sanded to 600 grit and then a scotch brite pad satin finish over that. I cleaned it with soap and water and then rubbing alcohol (didn't have any acetone on hand). I took a small plastic tub and filled it with water about three inches deep and dissolved as much salt in it as I could. I hooked the positive lead of a car battery charger onto the knife. The jaws of the clamp were resting on the tang edges at the ricasso. I hooked the negative lead to a steel pin and submerged both ends in the water.

I set the charger to 10 amps. I almost started with 50, but I figured I would try the lower setting first. When I plugged the charger in the steel rod began sizzling and bubbling and the blade started to blacken almost immediately. The blackening started at the edge of the blade and slowly moved toward the spine. After about 5 minutes 90% of the blade was black. At this point I unplugged it to take a look. The spot where I had the clamp, not where it was touching but the spot that was beneath the body of the clamp, was completely untouched. I also noticed that the edges that started blackening first looked more heavily etched than the rest. I moved the clamp to a different location and stuck it back in until it blackened the rest of the way. Probably about another five minutes.

I took it out, sprayed it with windex, and washed it in soap and water. I had also applied a doodle with a sharpie to see what woudl happen. It did partially block the etch, but the edges of the marks didn't hold up. The overall finish was inconsistent. I now this is probably not supposed to be a smooth, even finish. The edge of the blade and the exposed part of the tang were pitted. In fact the handle scales were sanded even with the tang edges before, and now they hang over slightly. The mid portion of the blade where it blackened about midway through the process actually looked pretty decent. After I buffed it with some steel wool it had a nice gunmetal grey type look.

I'm assuming the edges etched too much, the part I just described etched about right, and the rest didn't etch enough. I'm wondering what I could do to make it more consistant.

I just thought I would share the results of my experiment. I'm sure I'll learn a lot from your tutorial and some more trial and error.

[AUBE]

Originally Posted by cbsmith111

I know you're busy, so don't feel pressed to reply to this, but I did a little experimenting this weekend with a knife I made that didn't really turn out so I wasn't worried about ruining it.

The knife was made from A2 and had been hand sanded to 600 grit and then a scotch brite pad satin finish over that. I cleaned it with soap and water and then rubbing alcohol (didn't have any acetone on hand). I took a small plastic tub and filled it with water about three inches deep and dissolved as much salt in it as I could. I hooked the positive lead of a car battery charger onto the knife. The jaws of the clamp were resting on the tang edges at the ricasso. I hooked the negative lead to a steel pin and submerged both ends in the water.

I set the charger to 10 amps. I almost started with 50, but I figured I would try the lower setting first. When I plugged the charger in the steel rod began sizzling and bubbling and the blade started to blacken almost immediately. The blackening started at the edge of the blade and slowly moved toward the spine. After about 5 minutes 90% of the blade was black. At this point I unplugged it to take a look. The spot where I had the clamp, not where it was touching but the spot that was beneath the body of the clamp, was completely untouched. I also noticed that the edges that started blackening first looked more heavily etched than the rest. I moved the clamp to a different location and stuck it back in until it blackened the rest of the way. Probably about another five minutes.

I took it out, sprayed it with windex, and washed it in soap and water. I had also applied a doodle with a sharpie to see what woudl happen. It did partially block the etch, but the edges of the marks didn't hold up. The overall finish was inconsistent. I now this is probably not supposed to be a smooth, even finish. The edge of the blade and the exposed part of the tang were pitted. In fact the handle scales were sanded even with the tang edges before, and now they hang over slightly. The mid portion of the blade where it blackened about midway through the process actually looked pretty decent. After I buffed it with some steel wool it had a nice gunmetal grey type look.

I'm assuming the edges etched too much, the part I just described etched about right, and the rest didn't etch enough. I'm wondering what I could do to make it more consistant.

I just thought I would share the results of my experiment. I'm sure I'll learn a lot from your tutorial and some more trial and error.

First if you are using 10amps thats too high for most blades. I use 2-5amps and I etch quicker than I should because I'm usually aiming for a more rustic finish.

Your cathode (negative lead) should be at least the same size as your anode (knife) and if possible it should wrap around the blade. Areas on the knife closer to the cathode will etch faster. Using sheet metal wrapped around the inside of the cup works. Just don't touch the anode and cathode together! I took a snap of my cathode/cup I'll have in the tutorial which I should do tomorrow (I'm sharpening the batch of knives now so I'll have free time tomorrow)

Pitting is usually due to either etching too fast, sediment, or your mask failing. By sediment I mean something like salt precipitating in that area, or your mask failing and pieces falling down then catching on the blade. Anywhere there is something lightly stuck to the blade it will etch faster around the edges.

Something else that affects the etch rate is how hard the steel is. Harder steel will etch faster than soft.

The pic I'm attaching shows 2 examples... one is the heat treatment of the steel affecting the etch. The lines I etched in place extended all the way across the blade, notice that they are deep along the edge, but almost invisible along the spine and finger hole? Thats because that knife is differentially hardened and only the portion near the edge is fully hard. The softer areas etch much slower. Also notice the lines are black/etched? Those were actually the spots I covered with mask. I dipped the edge of some paper in paint, then put stripes. If the mask works well that area won't be etched at all. In this case I use a paint that I know "fails" during etching and will actually cause the masked area to etch faster. Why does it etch faster? Because when the mask fails it allows the etch to go through it, but there is still a lot of sediment in place. The area around each tiny grain of sediment etches faster (pitting), making that area etch faster than the rest of the blade. I use this process when I want a darker/rustic piece. Also notice you can see pitting between the lines on the blade? Thats sediment that started to fall off, slide down the blade, then caught and etched faster.

[ckluftinger]

Originally Posted by cbsmith111

I've been thinking about trying an acid etch finish on a blade. I've read about people putting things like mustard on the blade to get a splatter type finish. I was wondering if there is a different way to do this. What If I put spots of silicone or something like that in random spots and let it dry adhered to the steel before I put it in the etchant? Any chance of this or something similar providing good results? I hate mustard.

Also, does A2 even etch very well?

The reason mustard works is because it contains vinegar and salt. if you hate mustard, you can make a paste of flour, vinegar and salt. Dab it on unevenly, leave to dry, then immerse in hot bleach for a few minutes. Wash it off, and repeat four to six times, depending on how much etching you are looking for. Easy, fast, and the smell of bleach will make the wife think you cleaned the house...

[AUBE]

Sorry I haven't posted up the tutorial yet. I got busy with Christmas season then we got hit with the fringes of a hurricane which is causing daily internet and power outages. I have to catch up on some custom orders but I still plan on doing it.