What are the limits of sublimation printing on underwear?

Short answer: Sublimation is excellent on white or light polyester, but it has firm limits. The dye turns to gas under heat and bonds with polyester, so fabrics with little or no polyester give weak, washed-out colour; cotton-modal will not give the same result. Sublimation cannot print white or light colours onto a dark ground, because it adds colour rather than covering it. In all-over printing of cut panels or garments, folds and creases can leave white lines, and stretchy fabric may show the light base colour when it stretches. The heat needed can affect some elastane and fabric finishes. Use sublimation on polyester-rich, light-ground fabrics, design to hide stretch and creases, and test after washing.

Fibre limits

• Best on high-polyester fabrics with a white or light ground.
• Blends give weaker colour in proportion to polyester content.
• Cotton, modal and viscose do not take sublimation dye well.

Colour limits

• No white or light ink on dark fabric.
• Colours are transparent and influenced by the base colour.

Process limits

• Creases and folds cause white lines in garment or panel printing.
• Roll printing before cutting avoids most creases but needs careful pattern placement.
• Heat and pressure can cause shine, press marks or change in hand feel.
• Stretched fabric can show the light base, known as grin-through.

Testing

• Colour fastness to washing with ISO 105-C06.
• Rubbing with ISO 105-X12.
• Wash and dry samples according to the care label using an ISO 6330 procedure, then stretch and inspect.

Design tips

• Use busy patterns that hide small faults.
• Avoid large solid areas on high-stretch zones.
• Print roll fabric before cutting for all-over designs.
• Match thread colour to the main print colour so seams do not stand out.

When to choose another method

For cotton and modal blends, use digital reactive or pigment printing instead.

Answering the brand in the question

For cotton-modal boxer briefs, sublimation is the wrong process, however good the polyester samples looked. The brand can either move the style to a polyester-rich fabric, accepting a different hand feel and moisture behaviour, or keep the cotton-modal fabric and switch to digital reactive printing. For the sports underwear with white seam lines, the likely causes are panel printing with folds or poor alignment of printed panels at the seams. Printing roll fabric before cutting, with planned placement, usually solves most of these problems.

Heat and elastane

Sublimation needs high temperature and pressure. Some elastane and finishes can lose stretch, yellow or change hand feel under these conditions, so test the stretch and recovery of printed fabric, not only the unprinted base.

Limits

Results depend on fabric, paper, dye and press settings. Test each fabric.

Facts, recommendations and uncertainty

Established: sublimation needs polyester and a light ground, cannot print white, and can show creases and grin-through. Recommendation: use it on polyester-rich fabric and test after washing and stretching. Uncertain: the exact result on a specific blend until tested.

Sources and further reading

• ISO 105-C06:2010 — Colour fastness to domestic and commercial laundering
• ISO 105-X12:2016 — Colour fastness to rubbing
• ISO 6330:2021 — Domestic washing and drying procedures for textile testing

Standards and regulations are referenced by their published scope. Test parameters, cycles and pass levels should be agreed with your laboratory for the specific product; legal requirements should be confirmed for each destination market.