What is that black stuff?

AShearer

AShearer

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Nov 30, 2016
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In stamped logos, letters, thread lines etc. For example on knives that have a gig stamped logo like the NF Barlows or TC's, some of those stamped logos are black and some or more accurately perhaps after cleaning, the black is gone and the stamp is steel colored. Is this black just goop from the polishing process? Is there a "Right" look?
 
Is this with Carbon Steel Blades?
I think that it may be the original "slag" (forgive the use of the most probably incorrect term ) of the Forging process still left in the Nooks and Cranny's, I think the " look" looks right having this, I think ( again as I may not be correct here ) the Stainless do not have this obviously because of being a different metal and different processes?
 
If my understanding is correct, it is mill scale. The bolsters are stamped before polishing, and the polishing process can't get to the mill scale inside the recesses.
 
I've been wondering the same thing. At first it was hard to tell if was applied after the stamp because the amount varied with each knife. In some of my 77 Barlows for instance, more so with the the nickel silver bolsters, it was even and dark throughout. But on the latest run of 77 clip Barlows it was thinner or nonexistent in some areas. Even my older steel 77's were even and older TC's less so. Not complaining, it looks good to me either way.
 
Campbellclanman said:
Is this with Carbon Steel Blades?
I think that it may be the original "slag" (forgive the use of the most probably incorrect term ) of the Forging process still left in the Nooks and Cranny's, I think the " look" looks right having this, I think ( again as I may not be correct here ) the Stainless do not have this obviously because of being a different metal and different processes?
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Thanks Duncan. Yes the knives I'm talking about are all Carbon I guess that is a difference. I have a couple all ss, 154CM knives that don't have any blacking in the nooks and crannies.
 
Wurrwulf said:
If my understanding is correct, it is mill scale. The bolsters are stamped before polishing, and the polishing process can't get to the mill scale inside the recesses.
Click to expand...

That is what I suspected, although I wasn't sure what to call it. When I had Todd Davison make my drop point swell (sort of) with two thread lines the bolster, I wanted that blackened look just in the very thin thread lines. He treated the score lines with acid then neutralized with baking soda? This is what I was told anyway. (I think)

I like that look, but also like when it's like half and half or even all clean! So, I just like them all. :cool:
 
If you particularly like the look and want it to be uniform, get an ultra-fine Sharpie marker and blacken in the lines, then buff off any excess that gets up on the higher surface. It is easily removable with alcohol or other solvents if you don't like it later.
 
jc57 said:
If you particularly like the look and want it to be uniform, get an ultra-fine Sharpie marker and blacken in the lines, then buff off any excess that gets up on the higher surface. It is easily removable with alcohol or other solvents if you don't like it later.
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I probably would not do that. I was just thinking about how this happens. But thanks for the suggestion.
 
Slag is glass like stuff that was floating around on molten steel at the steel mill. It is placed there to keep the air away from the steel so it does not literally burn up like a sparkler and this slag stuff (also molten during the firing and pouring of the steel) scavenges impurities out of the steel and provides a way to separate the impurities from the steel. This big lump is a chunk of solidified slag. Actually this is a relatively tiny piece. I lived in a steel town as a kid and used to go to the mill with my dad some times. This stuff was eeeeevvvverrrrrywhere. Some of it is kind of pretty in its own way. Most of it was gray green with some lighter streaks in it. I put the black thing in the photo as a “color” reference . . . also the white paper. You can just see that the slag is green not black.

. . . annnnyway the heated and hammered end of this square steel rod . . .
. . . this is how a blacksmith makes a tongue depressor . . .

. . . this square steel rod has what you were talking about on it. It is “fire scale” or “mill scale”. Note that it did not rust but the bare cold rolled surface of the steel rod did rust right next to the heated and hammered fire scale area. In the second photo I was attempting to show the surface of the cold rolled square rod. Cold rolled means the surface will be as most expect steel to look shiny and reflective not black or blue and scaly. Hot rolled is the latter (blue / black and non reflective).



PS: the black stuff you are seeing may be buffing compound from polishing the blade. (?)







c
 
Wowbagger Wowbagger

You brought up a term I was wondering about.. you mentioned "hammer fired". GEC tubes always have "hammer tested" in large print on the front of their tubes. Is this related to "hammer fired"? What does this mean?
 
I've always wondered this, but never thought to ask! Good question and, as always, fantastic answers. :):thumbsup:
 
You get this in nail nicks too and I've had it on customs with stainless blades. I think it makes for a nice contrast all round in a detailing way.
 
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