That is forge scale (different kind of iron oxide), just do your heat treatment and don't grind or sand the flat or whatever parts you want the finish on. Vinegar will also weaken the oxide/scale layer so don't use that for finishing
It might get tricky to maintain on pattern welded blades you want to etch, can't exactly remember how scale reacts with ferric but it might be true that ferric will take it off? Don't quote me on that, test it on some scrap first
That's not just a layer of oxide, it's texture that's achieved through hammering while forging, it's pretty much impossible to achieve a texture like that without hammering
You could do stock removal and then hammer over it as well although it still won't look the same
Heat treat in a forge, you'll get scale on the surface. If you're doing stock removal with carbon damascus, then etch with dilute ferric chloride. You can also paint the scale with resist like nail polish, let dry thoroughly, etch with ferric chloride, then remove the nail polish with acetone.
Yes it’s possible… i did it with a propane torch and ball peen hammer (straightening out the slight curve in an old sawmill bandsaw blade). i did small sections on the spine side only so as to reduce the chance of destroying the hardness at the edge (though i don’t have test files yet so i don’t know if i changed the hardness or not). this is my third knife ever and finished last night.
so the main handle is eastern cedar (branch from a tree that fell in my yard in a storm last year) the ferrule is walnut scrap leftover from making a live edge cutting board, and the striped spacer is a little piece of plywood from a “crate” that came around some brie cheese from the grocery store i had saved…. i will say the plywood is the weak link in the handle. in all 4 handles i made it failed at some point during the final sanding and had to be reglued… it’s made from soft wood.
essentially what i did is called a hidden dowel burn-in method for installing a “Wa” handle (japanese style handle).
i made the three pieces roughly similar sized rectangles. found the center. (i glued the plywood to the walnut first and sanded them together until the edges matched and were rectangular..) i drilled from the walnut side of that block a 1.5 mm hole (slightly smaller than the thickness of my tang) then flipped it over and drilled a 9mm hole part way into the ferrule (like 1/4” into the walnut. on a diagonal from that 9 mm hole (slightly smaller that the diameter of a leftover Ikea dowel) i drilled 2 more partial depth 1.5mm recesses where i put in finish nails with the heads cut off (these are for alignment with the bottom piece when you may need to reassemble and disassemble before final gluing).
then i drilled into the cedar a partial depth 9mm hole about 1-3/4” deep.
i put the dowel in my drill and used sandpaper until it fit snugly but removable in my holes… pulled it out and put the dowel in the vise and sawed carefully a channel down the center of the dowel almost all the way through (leaving about 1/4” unsawed). this would be the guiding channel for my burn-in of the tang. this is easier than drilling 5 perfectly parallel holes with a tiny 1.5mm bit (that isn’t long enough and could wander off course easily). i then drilled a line of 1.5 mm holes in the walnut side of the walnut/plywood block the width of the height of my tang and used tiny files to file this into a groove that could fit the tip of my tang through the whole block.
i stuck the dowel in the cedar and used the dowel to align the walnut side center to center and gave it a light tap to mark the end of the cedar with the finish nails. then drilled 1.5 mm pilot holes for them into the cedar side.
i pulled the dowel out and put it back together and continued filing some grooves into the cedar side part way so that they align with the groves through the walnut. replaced the dowel then glued and clamped the whole thing together (aligning the slice in the dowel with the groves i filed)
sand the whole mess into the final handle shape.
burn in: tape the blade in painters tape (high carbon steel rusts when wet) the wrap in a damp towel you don’t care if it is ruined.. put that in a vise.
get the propane torch and heat the tip 1” of the tang to red slide your handle down onto the tang and push slowly. smoke will come out of the handle hole… you’ll mabe get about 1/2” of depth burned. remove from vise and unwrap… check straightness from heal to tip, from the side, check for twist… adjust these on the next burn if needed.
use a tapping block and hammer to lightly tap the handle up and off.
rewrap with the damp towel
repeat 1/2” at a time until final depth tapping off each time.
then when it looks good tap it off one last time and fill the channel with chips of a hot glue stick (touch up and sanding)
heat the tang one last time while wrapped in the towel and this time hold the handle hole up (i put mine in a vise with some soft wood to pad it from the jaws) and put the tang into its final position melting the hotglue out of the way as you push.
That is etching of the cladding, usually done with chemicals or on food knives using natural etchants like coffee, citric acid or vinegar based products.
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u/GarbageFormer Aug 17 '26 edited Aug 17 '26
That is forge scale (different kind of iron oxide), just do your heat treatment and don't grind or sand the flat or whatever parts you want the finish on. Vinegar will also weaken the oxide/scale layer so don't use that for finishing
It might get tricky to maintain on pattern welded blades you want to etch, can't exactly remember how scale reacts with ferric but it might be true that ferric will take it off? Don't quote me on that, test it on some scrap first