Permanent Marker Stain Test: Cortex 2 vs. Sofubi
Here’s a stain test I conducted using permanent marker on both Cortex 2 and sofubi (soft vinyl). I deliberately left the ink on Cortex 2 for an extended period to give it a chance to soak in, then used Mr. Color Thinner to remove the mark.
Cortex 2 handled the test well—the ink was completely removed without residue. In contrast, the ink was almost immediately absorbed into the surface of the sofubi, with pigment sinking deep into the material within seconds. This made complete removal extremely difficult, even with thinner.
The difference lies in the physical properties of each material. Cortex 2 is made from ABS (Acrylonitrile Butadiene Styrene), a dense, non-porous thermoplastic with a tightly packed molecular structure. This structure limits the penetration of foreign substances—so inks tend to remain on the surface longer, where they can be removed if addressed promptly. While ABS isn’t completely immune to staining, it is far more resistant than softer materials.
Sofubi, on the other hand, is a soft vinyl formed through a slush casting process. Its surface contains microscopic voids and a more open polymer matrix, which allows low-viscosity liquids—like solvent-based ink—to diffuse rapidly beneath the surface. Once the pigment settles, it bonds with the material at a molecular level, making it extremely difficult to extract.
This same vulnerability explains why certain fabrics or accessories can leave near-instant stains on sofubi—particularly on lighter tones, where even minimal absorption becomes much more visible. Lighter tones also contain less pigment overall, which provides less natural resistance to staining and makes any contrast more noticeable to the eye.
After cleaning, I used a melamine sponge to restore the matte finish on both materials. This worked well on Cortex 2, but for sofubi, the stain had already penetrated too deeply to fully recover the original appearance.
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