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Etching titanium to produce crystalline finish?

Q. Does anybody know the process by which this finish was produced? The picture linked below is of a Boker Orion folding knife, produced several years ago. The blade has a striking crystalline appearance.

The blade is titanium (unknown alloy) and has been etched so as to reveal the crystal structure with an overall light blue tint.

I am curious as to whether anybody who has etched titanium with the various acid formulations discussed (kroll's etch, oxalic acid ⇦ on eBay or Amazon [affil link] , KOH/H202, etc) has managed to produce similar results?

Patrick Lee
student - Baltimore, Maryland, USA
2006

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Q. Greetings, I am a chemist who recently started working in a plating laboratory. Knives and anodizing titanium have been a hobby of mine over this past year. Recently, a knife has been introduced (the Kizer Drop Bear) which features a titanium handle showing crystalline titanium. I have seen two other knives with such an appearance, but it doesn't appear too common. After researching online and this forum I found a method for showing crystalline titanium, but I cannot achieve such an appearance visible to my naked eye.

Grade 5 (aka TC4 or Ti6Al4V) titanium I sanded with course silicon carbide sandpaper, polished at 18,000 grit, and have tried etching with Kroll's and Weck's reagent (2mL 0f 50% HF and 4 mL of 70% HNO3 in 100 mL water and 5 g ammonium bifluoride in 100 mL water, respectively.) I have even tried anodizing at 12Volts DC in 50% oxalic acid solution as another suggestion mentioned. The only method I have found online which I haven't employed is a final step before etching in colloidal silica, but I don't have this reagent. Any information on this process would be appreciated.

Here is a video of the Kizer Drop Bear in crystalline titanium:
https://youtu.be/Fz4zQ80_HDc

A photo of an old Boker Orion with Titanium blade:

and a reproduction knife made in China with this finish:

Matthias Carroll
- Wenatchee Washington
April 14, 2023

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