A tri-blend jersey mixes three fibres, usually polyester, cotton and rayon, in one yarn. Each fibre brings something different. Polyester is strong and dimensionally stable, and because it dyes differently from cellulose fibres it creates the mottled heather look many tri-blends have. Cotton gives a familiar, natural hand and absorbency. Rayon, also called viscose, gives drape, a cool touch and softness. The ratio decides the balance between these.

What a higher rayon share does

More rayon generally means more drape and softness, and a slinkier fall on the body. Rayon can be weaker when wet and may shrink or distort more in washing, so a higher rayon share needs care in finishing and in the care label. In your example, 25% rayon will usually feel drapier than 13%.

What polyester does

Polyester holds shape, reduces shrinkage and dries faster. It can also make the fabric more likely to hold pills, because polyester fibres are strong and pills do not break off easily. Test pilling with a named method such as ASTM D3512 on washed fabric and agree a minimum rating.

Colour and heather effect

In a tri-blend dyed as fabric, the polyester and the cellulose fibres take dye differently, which gives the heather effect. Changing the ratio changes the look. Approve colour on the actual blend, and expect each colour to look slightly different between the two mills' fabrics even in the same shade name.

What to specify

Write the exact fibre ratio with the yarn count, construction, weight with a tolerance under a named method such as ASTM D3776, and shrinkage limits after a named wash procedure such as ISO 6330. Ask the mill to hold the same yarn supplier for the order. The fibre content on your label must match the actual blend; the FTC's Textile Rules, 16 CFR Part 303, set out how fibre content is disclosed.

How to choose

Have both fabrics made into tees, wash them several times, and compare drape, softness, shrinkage, twist and pilling side by side. Wear trials tell you more than swatches.

Once chosen, keep the approved washed tee as the reference for bulk and reorders.