In plastics manufacturing, few things cause more hidden problems than moisture—especially when it comes to color consistency and surface appearance. Even a small amount of residual moisture in your resin can create visible defects, internal weaknesses, and costly rework.

Many resins (especially hygroscopic polymers) naturally absorb moisture from the air. When these resins are processed at high temperatures without proper drying, the absorbed water doesn’t simply evaporate. Instead, it reacts with the polymer or boils into steam, causing a range of appearance and structural problems, including:

• Surface bubbles and voids
• Cloudiness or haze in transparent parts
• Poor surface gloss or matte patches
• Splay marks (silvery streaks)
• Color shift or yellowing
• Mechanical property loss (brittleness, reduced impact resistance)

Moisture causes hydrolysis—breaking down polymer chains during molding. In PET or nylon, this can lead to visible yellowing or darkening, even if the initial color match was perfect.

Boiling moisture expands rapidly during molding, forming bubbles beneath the surface or visible splay (silvery streaks).
In transparent or glossy parts, even minor moisture defects are magnified by the reflection and refraction of light—instantly ruining the visual appeal.

When processing opaque colors, trapped moisture can create inconsistent pigment distribution or microvoids that scatter light unevenly.
This results in parts that look patchy, translucent where they should be solid, or simply “off” from the approved standard.

Removing moisture ensures the resin behaves predictably, allowing pigments to develop the intended shade during melt processing.

Dry resin prevents bubbles, haze, and splay, maintaining the visual polish or texture designed for the part.

Beyond color, proper drying protects the mechanical properties of the resin—meaning parts won’t just look good, they’ll perform properly too.

When it comes to plastics processing, resin moisture isn’t just a material issue – it’s a color issue. Whether you’re molding precision parts from PET, nylon, or PC, improperly dried resin can sabotage your color targets, dull your surface finish, and create visible defects that erode customer confidence.

By taking resin drying seriously—and partnering with a color compounder that understands your process—you can eliminate guesswork, reduce scrap, and achieve vibrant, consistent results from prototype to production.