How to Pre-Wash and Pre-Treat Fabric Before Sewing

The question every beginner sewer hears at some point: “Did you pre-wash your fabric?” The reason it’s asked is that almost every fabric shrinks the first time it’s laundered, and the result of skipping that first wash is a garment that fits perfectly when finished and noticeably worse after the first time you put it through the washing machine. Cuffs ride higher; hems shorter; bodice tighter.

This guide covers what to pre-treat and how, organized by fibre type. The short version: most natural-fibre fabrics shrink 2–7% on the first wash. Synthetic fabrics shrink negligibly. The fabrics that need attention are the ones you’ll most often sew.

Why pre-treatment matters

Three things happen to fabric the first time it’s washed:

Shrinkage: fibres relax from the tension applied during weaving and finishing. The fabric becomes shorter and slightly tighter.
Loose finishing chemicals release: most commercial fabrics have starch, sizing, or surface treatments. These wash out over the first 1–3 cycles.
Dye release: if the fabric isn’t fully colourfast, it can bleed onto other fabrics in the same wash.

If you don’t pre-treat, all three happen after you’ve cut and sewn the garment — and the resulting changes in size, hand, and colour aren’t predictable. Pre-treatment standardizes the fabric to the state it’ll be in for the rest of its life.

When to pre-treat

A practical rule: pre-treat any fabric that you’ll wash the finished item the same way. For a tote bag you’ll throw in the wash, yes. For a wool dress that will only be dry cleaned, less critical (but still useful — see below).

Always pre-treat:

Cotton (any weave, any weight)
Linen
Rayon and viscose
Hemp
Silk noil and most non-luxe silks
Knit fabrics (jersey, ponte, etc.)
Fabric blends (cotton-poly, rayon-cotton, etc.)
Denim — especially raw or non-sanforized denim, which can shrink dramatically

Optional pre-treatment (depending on care plan):

Tailored wool that will only be dry cleaned (a steam treatment is common in lieu of washing)
Silk charmeuse or other delicate silks (a gentle hand-wash equivalent)
Special-occasion fabric used once

Skip pre-treatment for:

Pre-shrunk fabric (label may say “sanforized” or “pre-washed”)
Fabric meant strictly for non-laundered use (upholstery, decorative)
100% polyester or nylon (negligible shrinkage)

How to pre-treat by fibre

Cotton

Wash cotton fabric the same way you’ll wash the finished garment.

Quilting cotton, lawn, voile, poplin: machine wash on the cycle you’ll use for the finished item (warm/normal for everyday cotton), tumble dry. Iron when slightly damp.
Heavy cotton (denim, canvas, twill): machine wash on warm or hot, tumble dry on medium. Heavy cotton can shrink 5–8% the first wash. Some sewers wash twice for safety on raw denim.
Cotton with stretch (cotton-spandex blends): machine wash on cold, tumble dry on low. The spandex content can lose elasticity at high heat.

After washing, iron flat. Don’t skip this — the fabric’s behaviour during cutting depends on it being smooth.

Linen

Linen shrinks more than cotton — sometimes up to 10% on the first wash. Pre-treatment is non-negotiable.

Machine wash on warm with regular detergent.
Tumble dry on medium, or air dry. Linen softens with each wash and develops a beautiful drape over time.
Iron while damp on a high steam setting. Don’t try to iron dry linen flat — it doesn’t cooperate.

For linen you intend to keep crisp (not soften), wash twice on cold and air-dry. The fabric still loses shrinkage but stays closer to its original hand.

Rayon and viscose

Rayon shrinks significantly and can warp out of shape during washing. Treat carefully.

Hand-wash in cool water with mild detergent, or machine wash on the delicate cycle in a mesh bag.
Air dry flat. Tumble drying rayon ranges from “loses shape” to “ruined.”
Iron on medium with steam.

Some rayon labels say “dry clean only.” If you intend to actually dry clean the finished garment, dry clean the fabric pre-cutting; if you intend to hand wash, hand wash now.

Wool

Wool is rarely washed. Most wool fabric comes pre-shrunk in the mill and won’t shrink further unless you actively try to.

For wool that will be dry-cleaned: skip washing. Optionally steam-treat by hovering an iron on the highest steam setting just above (not on) the fabric. This removes any residual shrinkage and chemical treatments.
For washable wool (modern washable wool fabrics, marked as such): hand-wash in cool water with wool-specific detergent (Eucalan, Soak), lay flat to dry.

Never wash standard wool in hot water — it felts and shrinks dramatically.

Silk

Most silk requires gentle handling.

For silk noil, silk dupioni, and other less-delicate silks: hand-wash in cool water with mild shampoo or wool detergent. Roll in a towel to remove water; lay flat to dry.
For silk charmeuse, chiffon, and other delicate silks: dry clean if you intend to dry clean the garment, or hand-wash gently otherwise. Tests on a small fabric corner first — some dyes bleed.
Iron on the lowest setting, while slightly damp, with a press cloth to prevent water spots.

Knit fabrics

Knit fabrics shrink and can warp out of shape during washing. Treat the way you’ll treat the finished garment.

Cotton jersey, modal, rayon jersey: machine wash cool, tumble dry low or air dry flat.
Ponte, scuba (polyester-heavy knits): machine wash cool, tumble dry low. Less shrinkage than cotton knits, but the spandex stays healthier on cool wash.
Wool jersey: hand-wash or use the wool cycle on a modern washing machine.

Lay knits flat to dry when possible — hanging stretches them out of shape.

Synthetic fabrics

100% polyester, nylon, or acrylic typically don’t shrink. But pre-treatment still serves two purposes:

Removes any sizing or factory treatments.
Cleans fabric that’s been on a bolt for months collecting dust and store smells.

Machine wash on cool or warm, tumble dry low. Iron on the polyester setting with a press cloth — direct high heat melts synthetic fibres.

Denim — special considerations

Denim is its own pre-treatment category.

Sanforized / pre-shrunk denim: minor shrinkage, follow standard cotton process.
Raw, unsanforized denim: dramatic shrinkage (up to 10% in length, 5% in width). Some sewers soak raw denim in hot water 1–2 times before sewing. Others embrace the shrinkage as part of the denim character — sewing a generous garment that shrinks to fit.
Stretch denim: machine wash cool to preserve elasticity.

Test your specific denim by washing a 30 cm × 30 cm square first and measuring before and after if you want to be precise.

After pre-treating: dealing with shrinkage

Typical shrinkage rates by fibre — useful for budgeting fabric purchase:

Fibre	Typical shrinkage	Notes
100% cotton (woven)	3–5%	Higher for heavy weaves like denim (up to 8%)
100% cotton knit (jersey)	5–10%	Knits tighten in the wash significantly
Linen	4–7%	Often shrinks unevenly; expect more in length
Wool (machine washable)	1–3%	Hand-wash or steam-only treatment recommended
Wool (traditional, dry-clean)	0–2%	Steam-shrink before cutting; minimal water exposure
Silk	2–5%	Hand-wash with care; many silks shouldn’t be machine-washed
Rayon / viscose	5–10%	Major shrinker — pre-wash always
Polyester	<1%	Stable; pre-wash mainly for sizing/finish removal
Polyester blends	1–3%	Depends on blend ratio

This is why patterns recommend buying 10–15% extra fabric. The shrinkage allowance protects you from the most common pre-treatment surprises.

If your fabric shrinks unevenly (often happens on linen and heavy cotton), the fabric edges may pull diagonally — the fabric is “off-grain.” Before cutting:

Pull the fabric on the bias (corner-to-corner) gently to re-square it.
Iron with light steam to relax the fibres back into a square.
Pull a single weft thread across the fabric width near the cut end and follow that thread line to square the cut edge.

For more on accurate cutting after pre-treatment, see our cutting guide.

Handling specific issues

Bleeding dye

Test colourfastness before washing if you’re unsure: dampen a small corner of fabric with water and press a white cloth firmly against it. If the white cloth picks up dye, the fabric isn’t fully colourfast. Wash separately the first time.

Wrinkling that won’t iron out

Some fabrics — especially linen and rayon — wrinkle stubbornly. The trick is to iron while the fabric is still slightly damp. If you let it dry fully, get it lightly damp again before pressing.

Pre-treating PDFs and pre-cut quilt fabric

Pre-cut quilt fabric (5-inch squares, fat quarters) is often pre-shrunk by the manufacturer, but not always. If unsure, wash in a mesh bag to prevent fraying — some pre-cuts unravel completely without this protection.

PDF-pattern fabric needs pre-treatment as much as fabric from a bolt; if anything more, since you may have been storing it for a while.

Pressing after pre-treatment

This step is non-negotiable. Cutting wrinkled fabric guarantees pieces that don’t lay flat, alignment errors, and seams that don’t match. Press:

All cottons on the cotton setting, with steam.
Linen on linen setting, with steam, while damp.
Wool on wool setting, with steam, using a press cloth.
Silk on silk setting, with low temperature, with a press cloth.
Synthetic on the synthetic / nylon setting (low), with a press cloth — direct high heat melts.

A flat fabric is one of the highest-leverage ways to make beginner sewing look professional.

Storage between pre-treatment and cutting

If you don’t cut immediately:

Fold fabric loosely along the lengthwise grain and store rolled rather than tightly folded (less crease memory).
Keep out of direct sunlight (UV degrades dyes and fibres).
Store flat, not bunched in a bag — bag storage produces sharp creases that take serious ironing to remove.

Pre-treated fabric is stable in storage for months as long as moisture and direct light are kept off it.

Closing thought

Pre-treatment is the unglamorous step every beginner sewer wants to skip and every experienced sewer never does. Twenty minutes of pre-washing and pressing prevents hours of frustration when your finished garment shrinks and stops fitting. The rule is simple: if you’ll wash the finished item, wash the fabric first.

Once your fabric is treated, pressed, and cut, the next consideration is needle and thread choice — see our guide to choosing the right needle and thread for every fabric.