Strange pattern

Albert · 15th July 2026, 10:01 PM

Has anyone seen a pattern like this on a sword blade?
What is it, and how should I treat it?
Any thoughts are welcome.

The sword is a Sumatran Cot Jang.

A. G. Maisey · 15th July 2026, 10:42 PM

This is a laminated blade that has been produced from ferric material with varying levels of carbon, it is also possible that the entire blade was quenched during heat treat, rather than just the cutting edge. It is possible that the lighter coloured material contains some nickel, it could well be iron from Sulawesi.

Personally, I would simply oil & use steel wool on it, the variation in blade colour tells a story.

Battara · Yesterday, 01:38 AM

I'm with Alan. Oil and enjoy.

Albert · Yesterday, 10:10 PM

Thank you both for your comment.

A. G. Maisey · Today, 01:09 AM

Albert, I'll add one other little comment. This blade was demounted for clean & stain, when it was remounted the tang was heated to permit insertion into the jabung used in the hilt to secure it, during this process the ricasso reached a heat of about 280-300C, this is not a bad thing & is quite common when remounting a blade. The colour in the ricasso is the evidence of this.

15th July 2026, 10:01 PM	#1
Albert Member Join Date: Jun 2005 Location: The Netherlands Posts: 213	Strange pattern Has anyone seen a pattern like this on a sword blade? What is it, and how should I treat it? Any thoughts are welcome. The sword is a Sumatran Cot Jang. Attached Images

Yesterday, 10:10 PM	#4
Albert Member Join Date: Jun 2005 Location: The Netherlands Posts: 213	Thanks Thank you both for your comment.

15th July 2026, 10:42 PM	#2
A. G. Maisey Member Join Date: May 2006 Posts: 7,241	This is a laminated blade that has been produced from ferric material with varying levels of carbon, it is also possible that the entire blade was quenched during heat treat, rather than just the cutting edge. It is possible that the lighter coloured material contains some nickel, it could well be iron from Sulawesi. Personally, I would simply oil & use steel wool on it, the variation in blade colour tells a story.

Yesterday, 01:38 AM	#3
Battara EAAF Staff Join Date: Dec 2004 Location: Louisville, KY Posts: 7,415	I'm with Alan. Oil and enjoy.

Today, 01:09 AM	#5
A. G. Maisey Member Join Date: May 2006 Posts: 7,241	Albert, I'll add one other little comment. This blade was demounted for clean & stain, when it was remounted the tang was heated to permit insertion into the jabung used in the hilt to secure it, during this process the ricasso reached a heat of about 280-300C, this is not a bad thing & is quite common when remounting a blade. The colour in the ricasso is the evidence of this.