Wash Inside Out: Always turn the chinos inside out before laundering to protect the outer surface from friction and "frosting" (premature fading).

Cold Water Wash: Use a cold-water setting ($30\text{°C}$ or below) with a specialized liquid detergent for dark colors to lock in the onyx hue.

Gentle Cycle: Avoid heavy-duty cycles; a gentle or permanent press setting will minimize stress on the seams and fabric.

Line Dry in Shade: Air drying is the best way to prevent shrinkage. Hang the pants in a shaded area away from direct sunlight, which can cause the black dye to oxidize.

Low-Heat Steaming: For a crisp look, use a garment steamer. If using an iron, keep it on a medium-low setting and iron on the reverse side to avoid creating shiny marks on the fabric.

Disclaimer: Color may vary slightly due to lighting or screen settings.