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Do .STL Files Contain Color Information?

If you’re familiar with 3D printing, you’ve probably heard of STL files. STL is the first 3D file format ever developed for 3D printing. Invented in 1987, it is a fundamental part of 3D printing – however, it does have some drawbacks and cannot capture all of the details you may want in a model. 

.STL Files don’t contain color information, although there are a few exceptions to this rule. Generally, STL files map out the surfaces of 3D objects using tessellated triangles. This creates a model with a hollow body in a uniform color without texture. 

If you want to learn more about how STL files work and how you can optimize your file formats for coloration in your 3D print, stick with me. I’ll tell you about how an STL file stores your model, how you can colorize it, and the best ways to add other colors and textures to your designs. 

How Does a .STL File Work? 

When you choose to use an STL file to print a 3D object, you must understand how the file format works to get the best results.

“STL” either stands for “standard triangle language,” “stereolithography,” or “standard tessellation language.” No one is sure exactly which one is the right option as the file format does all of these things. STL files map out a surface with tessellated triangles, using code to preserve them. 

Regardless of the name, an STL file always creates objects using small triangles, which are then tessellated over a 2D surface to pinpoint the parameters of a 3D object. An STL file maps out the surface of a model, covering each plane like a 3D puzzle filled in with small triangular pieces. 

STL is usually the best file format for simple, monochrome objects because it uses a geometric approach to map out surfaces. Many people call it an “industry standard” since it’s the oldest 3D printing format, and most 3D printers can support it. 

That said, the STL file format has some limitations when it comes to modeling for 3D printing. STL files only map out the surface of an object. That means that they do not contain details about colors, texture, or the inside of the model. 

What Is a Colored STL File? 

You may have noticed that I said that STL files generally don’t contain color information, with some exceptions. Those exceptions are colored STL files. 

Colored STL files are tessellated 3D models that preserve colors you apply to your model in your CAD software. They allow you to save the color information of your model without converting it to a different file format. However, developing and perfecting colored STLs is a challenge. 

So, although it’s possible to get colored prints from STL file formats, using colored STL files isn’t always the easiest way to add color to your model. 

As time goes on, painting and coloring STL files has gotten more accessible. However, for the most part, it’s still far too outdated a format for color printing. When you want filament or color changes, it’s usually easier to opt for another file format. 

That’s because, in order to color an STL file before you export it, you’ll either have to use a paint tool explicitly made for STLs or unwrap your STL into 2D planes, then paint each one individually. 

Both of these processes can be demanding and time-consuming. In addition, they usually result in jagged, pixelated colors with triangular and uneven edges. However, with enough practice and dedication, you can develop impressive skills for painting and coloring STL files.  

Another downside to using STLs for color printing is that you need to print a large transition tower to keep your colors from mixing in the nozzle. 

These blocks keep your colors from blending when the printer switches colors, and they ensure that the colors of your print are sharp and clean. However, they also waste tons of filament, making each print more expensive and time-consuming. 

While engineers and software designers are working on making transition towers smaller and more practical, they haven’t entirely developed the technology enough to eliminate them yet. So, as it stands, you have to accept that you’ll need quite a bit of filament to 3D print even the smallest multi-colored STL file. 

If you want to venture into uncharted 3D printing territory and try out a colored STL, some of the best software for creating colored STL files are Mosaic Canvas and Meshmixer. These painting and modeling tools are ideal for creating colored STLs, and there aren’t many other options out there. 

For an example of how you can “paint” STL files for 3D printing using Mosaic Canvas, check out this Youtube video from 3D Printing Nerd: 

If you’re using Meshmixer to color your STL files, you can use this tutorial from 3D Chameleon as a helpful guide: 

3D Printing File Formats That Include Color

If you want your print to include changing colors, you can use any of several different file formats, which I’ve listed below. 

I highly recommend using one of them to incorporate colors into your model because they’re much easier to use and design than colored STL files. If you can, you may want to convert STLs into these file formats before you add coloration to your model. 

Some of the best 3D printing file formats that include colors and textures are: 

  • .OBJ files
  • FBX
  • 3MF

These file formats are ideal for multi-colored designs, intricate details, and textures since they use smaller polygons to map out the surface of your 3D print. They’re also much easier to color because you won’t have to fight against the triangular design of your model. 

Final Thoughts

STL files don’t usually contain color information, and coloring them for multi-color printing can be challenging since the format does not naturally support colors. That said, you can attempt to color STLs using specific software like Mosaic Canvas and Meshmixer. However, most printers generally recommend changing formats to an OBJ, FBX, or 3MF file for the best results when printing colors.