Unsanforized cotton shrinks. This is not a defect — it's the natural behavior of cotton fibers that have been under tension during knitting and finishing. When that tension is released by heat and moisture in the wash, the fibers contract. The result is a garment that can shrink 5–10% after the first wash, which destroys size consistency across a production run.
Sanforized (or pre-shrunk) fabric has been mechanically compacted before cutting and sewing — forcing the fibers to contract in a controlled environment before the garment is made. Residual shrinkage after sanforizing is limited to less than 3%, which is acceptable for consistent sizing and prevents customer fit complaints.
Always specify sanforized or pre-shrunk fabric in your tech pack — especially for heavyweight jersey. Unsanforized fabric can shrink 5–10% after first wash, which makes your size spec irrelevant.
Why shrinkage matters for sizing
How the process works
The Sanforized® process (a registered trademark of Sanfor LLC, now used generically as "pre-shrunk") passes the fabric through a compaction unit — a rubber belt that physically compresses the fabric in the length direction, forcing the fibers into a shortened, stable configuration.
The fabric is simultaneously dampened with steam and then dried under controlled tension. This sets the fibers in their compacted state. When the garment is subsequently washed, there is minimal remaining capacity for further contraction — most of the shrinkage potential has already been eliminated at the fabric stage.
Production specs for your tech pack
| Spec | Value | Notes |
|---|---|---|
| Finish type | Sanforized / Pre-shrunk | Mechanical compaction process |
| Residual shrinkage | Max 3% | After 3 wash cycles at 40°C |
| Test standard | ISO 6330 | Standard shrinkage test method |
| Application | Fabric stage | Applied before cutting — not a garment-stage process |
| Measurement spec | Post-wash | All POM measurements taken after 3 washes |
In FlatLabs PRO, the sanforized spec is automatically included in the fabric section of your BOM for heavyweight jersey — where shrinkage is highest and pre-shrinking is most critical for sizing consistency.
Important: always specify that your POM measurements are taken post-wash (after 3 wash cycles). Measurements taken on unwashed fabric will not reflect the garment the customer receives.