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Finnish Company Develops Laser That Can "Paint" Colors Onto Metal!

Cajo lasers can produce "all the colors of the rainbow onto stainless steel" and other materials

By Rain Noe - October 11, 2016

in Tech

Yeah, so this is crazy: Finland-based Cajo Technologies has figured out how to use a laser to burn colors into different materials. "Our patented technology creates extremely precise, permanent and practically everlasting marking or colour patterning on almost any material without additives or pigments," the company writes.

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Here's a quick video of the laser laying down red:

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It's tough to tell with the lousy videography, but in this second video the finished red appears to even be gradated:

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Like you, I'm wondering how the heck this works--and the company ain't saying. All they'll reveal is that

[Our] color patterning and marking method is based on a unique innovative application of the traditional laser beam. [It] alters the surface structure of the material, and no additives or pigments are needed. The method allows for extremely precise, permanent and practically everlasting colour patterning on almost all materials.

Though the company states that they can do metal or plastic, all of the colored samples shown by the company appear to be on stainless steel.

Lastly, here's a sample of some of their other, non-color applications:

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Robert Wilkey

8 years ago

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Now that I look at it, the color range matches up with the range of colors achievable through heat-treating of stainless steel. So my guess is they figured out how to fine-tune the speed of the galvo laser to accurately heat the surface of the steel to a specific temperature range.

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Robert Wilkey

8 years ago

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My guess is that its either a function of heat-treating (which usually only gives a range of yellow/orange/purple/blue/turquoise) or microscopic 'structural coloration' like that of a butterfly's wing (which would be impressive, since that level of microscopic accuracy with a galvo laser seems nigh-impossible). Either way, very impressive, and I can't wait to see the array of applications this will be used for.

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Michael Saggese

8 years ago

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It looks like it might be a surface-level tempering to get the colors. Not really sure though.

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Michael Reilly

8 years ago

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This uses a YAG or Fiber laser which is 1/10th the wavelength of CO2 lasers that are commonly used for cutting wood and acrylic. The different wavelength makes it ideal for marking on and cutting metal, but it can't cut most of the common things CO2 lasers will. Because it's 1/10th the wavelength, the laser spot can also be close to 1/10th the size. Laser power is a measure of power over area, so watt for watt, YAG/Fiber is basically 10X more powerful.

What they're doing here is heating small areas of the metal very quickly. Metal is a very good conductor of heat, which is why cutting metal is harder than it seems like it should be. But the combination of high power and small spot size, allows them to rapidly heat a small spot of metal. When heated, the metal reacts with oxygen in the air to grow an oxide coating (similar to rust). The coating is always the same composition, but varying the amount of time heated varies the coating thickness. The different thicknesses refract light differently, and cause us to see different colors.

Here is a scientific paper exploring the process. The company above has refined it into a repeatable process. Very cool!
http://www.vtt.fi/files/research/ism/manufacturingsystems/relation_of_laser_parameters_in_color_marking_of_stainless_steel.pdf

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- Michael Reilly
  
  Michael Reilly
  
  8 years ago
  
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  Looks like it clipped the address. Hopefully this works:
  www.tinyurl.com/colormarkingstainless
  
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Yash Nagda

8 years ago

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It seems like they're changing the pulse frequency and etching speed to vary the amount of heat applied at a point, which can be used to carefully control the thickness of the oxide film. Heat treating results in the exact same oxide formation. The colors occur due to the thin film effect, which is the same reason why you see colors in puddles after the first rain and why soap bubbles look multicolored.

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ThirtySomething Nerd

8 years ago

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I agree with the heat treatment comments. Also appears to include some "halftone" like effects to achieve additional colors and shades. Interesting to consider that while this process appears to produce color, it's more like grey-scale in that it contains only one dimension of information at any point (thickness of oxide layer from heat treatment). Another video of the same process shows the laser passing twice over a "green" patch (which may be more telling of the process than anything else).

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