San Mai etching question

D

dwaterfield

Joined
Feb 24, 2022
Messages
115
I am working on my first attempt at san mai and have a question or two. Overall I am happy with how creating the billet and shaping the blade went - this was also some of my first welding and only my third or fourth attempt at forge welding.

The billet was 2 layers of 15n20 around one 1095. Shaped the blade, ground and then hand sanded to 600 grit. Heat treated in the forge at 1475 (approximately) for 10 minutes, quenched in warm vegetable oil, then tempered twice at 400 degrees for 2 hours.

This morning I sanded again to 600 and then attempted etching in 3:1 distilled water to ferric oxide. The results are underwhelming.

The good news is I can see the line between the steels on both sides. The bad news is that the difference between them is hard to see.

Below are three pictures. The first is before etching. The second is after etching for 30 seconds. The third is after neutralizing with Windex, followed by light sanding with steel wool.

What can I do to get a more dramatic difference between the layers of steel? I assume something is wrong about the way I am doing this but I think I am doing what I have seen others do online and what I have read here and other places. I must be missing something!

Edit: I have tried shorter and longer etching times, up to 2 minutes. Also tried sanding with 1000 grit in between etches. The results are about the same.

TIA, Doug
https://flic.kr/p/2ohZocQ
https://flic.kr/p/2oi1zZz
https://flic.kr/p/2ohVp38
 
You said ferric oxide, do you mean ferric chloride?

Your etchant is bad. It should start to darken it immediately.

Hoss
 
Before the etch it needs to be COMPLETELY clean.
Wash with hot water and dish soap. Wash and rinse again. Wipe off with alcohol and let dry. Do not touch the blade except the tang.

1) Etch in new Ferric chloride diluted 1:3 with water (bottled water works best).
2) Etch for 5-10 minutes. The darkening should be almost immediate, but I like to get the etch into the surface a bit.
3) Pull out every few minutes and rinse off well, wipe off with a clean paper towel, rinse well, then put back in the etch tank I use the garden hose for this.
4) Once done, rinse off well and boil in a pot of water and teaspoon of TSP. (1/2 teaspoon of baking soda can be used if you don't have any TSP)

If that doesn't work something isn't right with the steels.
 
Last edited:
Stacy E. Apelt - Bladesmith said:
Before the etch it needs to be COMPLETELY clean.
Wash with hot water and dish soap. Wash and rinse again. Wipe off with alcohol and let dry. Do not touch the blade except the tang.

1) Etch in new Ferric chloride diluted 3:1
2) Etch for 5-10 minutes. The darkening should be almost immediate, but I like to get the etch into the surface a bit.
3) Pull out every few minutes and rinse off well, wipe off with a clean paper towel, rinse well, then put back in the etch tank I use the garden hose for this.
4) Once done, rinse off well and boil in a pot of water and teaspoon of TSP. (1/2 teaspoon of baking soda can be used if you don't have any TSP)

If that doesn't work something isn't right with the steels.
Click to expand...
Thanks Stacy. I will try cleaning and going for a longer etch. Two questions.

In step 3 you mention pulling out every few minutes and rinsing. Just to make sure -- this is not several 5-10 minute cycles, just one in which you are rinsing periodically?

Also what is TSP? I do have baking soda. How much boiling water should be used with the 1/2 tsp of baking soda?
 
TSP - Tri Sodium Phosphate. It is a cleaner you can get at the hardware store or pool supply. Powerful stuff. Also works as a great acid neutralizer.

Yes, 1 acid 3 water, I typed it backward. I corrected it.
You pull the blade every couple minutes and clean the sludge off then put back again. The total time is usually 5-10 minutes, I sometimes etch damascus for 20-30 minutes to get the right topography.
 
Stacy E. Apelt - Bladesmith said:
TSP - Tri Sodium Phosphate. It is a cleaner you can get at the hardware store or pool supply. Powerful stuff. Also works as a great acid neutralizer.

Yes, 1 acid 3 water, I typed it backward. I corrected it.
You pull the blade every couple minutes and clean the sludge off then put back again. The total time is usually 5-10 minutes, I sometimes etch damascus for 20-30 minutes to get the right topography.
Click to expand...
Whew! Thought I had wasted the acid.

I will look at getting some TSP. For now in the shop trying 2 minute cycles with rinsing.
 
So after 5 cycles of etching and rinsing the whole blade is definitely much darker but there isn't a big difference between the two steels. The first picture is just after the last rinse, water stil on the blade. The second picture is after boiling in a liter of distlled water and a 1/2 tsp of baking soda, then wiping off with a clean paper towel.

I wondered if I had somehow managed to do all one steel, but I checked the box of steel I ordered and 2 pieces of 15n20 are gone and one of 1095. Unless the manufacturer mislabled them I should have the right layers.

Should I try polishing with steel wool or will that just remove the etching?

Thanks for all the advice.

https://flic.kr/p/2ohZkvp
https://flic.kr/p/2ohWHYc
 
When you do the etch, can you see the dark core on the spine? It really looks like you've not got the 1095 exposed at the bevel, still with 15N20 covering the core. If you can't see the 1095 core on the spine, I'd suspect you've got 3 layers of 15N20. Easy to do.
 
Ken H> said:
When you do the etch, can you see the dark core on the spine? It really looks like you've not got the 1095 exposed at the bevel, still with 15N20 covering the core. If you can't see the 1095 core on the spine, I'd suspect you've got 3 layers of 15N20. Easy to do.
Click to expand...
Hey Ken, good idea to look at the spine. I don't see a difference there. I can see the forge weld line on the blade, though it is faint I think you can see it in the pictures above.

I am always willing to believe I messed up, but I just looked again in the box from Hermit Tools. I had 6 pieces each of 1095 (red paint on the ends) and 15n20 (yellow paint). Now there are 5 red and 4 yellow so I am pretty sure I had the right layers.

Idk. Tempted to clean up pieces of each steel and just etching them to see if there is a difference.
 
I wonder if the blade didn't harden properly? Unhardened metals etch differently/lighter than hardened steel. The etching looks weird, too, little dark dots all over?
 
I'm having the same issue with a blade I just finished. 1095/15n20 Damascus. I finally gave up and put a handle on it. Maybe we got the steel from the same place and it's not what they advertised?
 
banjobend said:
I'm having the same issue with a blade I just finished. 1095/15n20 Damascus. I finally gave up and put a handle on it. Maybe we got the steel from the same place and it's not what they advertised?
Click to expand...
Maybe? I got mine from Hermit Tools. It is the first purchase I have made with them.

DevinT said:
From the picture, your etchant is too strong. Try diluting it down.

It might be poor heat treating or not actually 15n20 also.

Hoss
Click to expand...
Pretty sure my math was right on the solution, but it's certainly a possibility. I assume I'd need to sand back to shiny metal and then re-etch?
 
How much did you grind away after HT?
You may still have a good layer of decarb on the blade. You have to take off a good .010" per side on most blade after HT.

Looking at the image you posted I would almost think all three layers were all 15N20.
 
banjobend said:
I got mine on Amazon, but guess who the seller is? Hermit tools. Might be onto something.
Click to expand...
I believe I purchased through Amazon as well. Could be coincidence but maybe not. I am going to grind the ends on the remaining steel and etch those. I saw an image where someone did that who forgot which steel was which. Even without heat treat the difference in darkness between steels was obvious.
Stacy E. Apelt - Bladesmith said:
How much did you grind away after HT?
You may still have a good layer of decarb on the blade. You have to take off a good .010" per side on most blade after HT.

Looking at the image you posted I would almost think all three layers were all 15N20.
Click to expand...
I ground at 220 grit and then hand sanded to 600. I did not measure but I think it's likely I removed that much.

I just tried hand sanding back down to shiny steel. The forge weld lines on both sides noticably changed, but there still is not much color difference. The blade is thin enough that the edge is starting to sharpen.

Tomorrow I will see what I can do to determine if I actually have received different steels.
 
dwaterfield said:
Maybe? I got mine from Hermit Tools. It is the first purchase I have made with them.


Pretty sure my math was right on the solution, but it's certainly a possibility. I assume I'd need to sand back to shiny metal and then re-etch?
Click to expand...
I’m sure your math is fine, still needs to be diluted.

Hoss
 
Just an update: there are multiple reviews on Amazon now saying that the 15n20 they received from Hermit Tools did not etch correctly and seems to be high carbon steel, not nickel steel. I'm going to see what I can do to get my money back.

EDIT: I originally wrote "stainless steel" instead of "nickel steel"
 
Last edited:
You must log in or register to reply here.
Back
Top