Mold and injection molding: colours and finishing in plastics

The aesthetic and functional quality of an injection moulded plastic parts depends on several combined factors: polymer colouring, mould surface finish, plastics finishing and dedicated post processing.

EPS works on every factors of a new project about polymer colouring, mold surface finish, surface treatments and dedicated post processing. EPS supports  every project by ensuring repeatable, stable results that fully align with the required technical specifications.

Colouring plastic part: how it works

Plastic parts can be coloured in different ways. We mainly use coloured pigments added to the material (masterbatch), precoloured polymers, and special additives designed to achieve specific visual effects.

Factors influencing the plastic part finishing

The final colour depends on the type of polymer, injection moulding parameters, mould characteristics and the presence of additives within the material.

Mold finish and part finish: the differences

When discussing finishes, it’s important to clarify that the mould’s surface finish is the first variable that defines the appearance of the moulded part. However, it doesn’t always match the final finish of the plastic component, which can be further modified through additional treatments. Depending on the desired result, EPS’s tooling department can apply mirror polishing, satin finishing, texturing or sandblasting. EPS controls all parameters, like polymers shrinkage, injection systems, temperature conditioning and polymer characteristics, to guarantee consistent aesthetic and functional quality.

Surface finishes and final treatments

Beyond the finish obtained directly from the mold, additional treatments can enhance the component’s appearance, durability or functionality. EPS offers:

• Painting for glossy, matte, soft‑touch or metallic effects
• Screen printing for logos, text and symbols
• Pad printing for precise decoration on complex surfaces
• Laser marking for permanent engravings and identification codes
• Chroming for high‑resistance metallic finishes
• UV treatments for protection against fading and degradation

EPS can also apply labels and create dedicated packaging solutions.

A Complete and integrated service

EPS SRL provides a fully integrated service: consulting on polymer and colouring method selection, mould design with tailored finishes, customised surface treatments, aesthetic and dimensional quality control and mass production.

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With extensive experience in the polymers field, we support customers from the design phase all the way to final product delivery, ensuring consistency, aesthetic quality and high technical performance.