A hot wash with plenty of agitation removes most fabric sizing. For stubborn cases, adding washing soda or an enzymatic detergent to the load breaks down the coating faster. The best approach depends on what type of sizing was applied and what kind of fabric you’re working with.
What Sizing Is and Why It’s There
Sizing is a coating applied to yarns during weaving to strengthen them and prevent breakage on the loom. It gives new fabric that crisp, smooth feel you notice when you unroll yardage from a bolt or pull brand-new sheets out of the packaging. Natural starch and its derivatives account for roughly 75% of all sizing agents used in the textile industry worldwide. The rest are synthetic polymers, most commonly polyvinyl alcohol (PVA), which dissolves in water and forms a thin film around fibers.
You might also encounter carboxymethylcellulose (CMC), a plant-derived sizing common on cotton, or acrylic-based sizing on nylon fabrics. Each type dissolves under slightly different conditions, which is why a single wash doesn’t always do the job.
Why You’d Want to Remove It
If you’re sewing, sizing masks how the fabric actually drapes and handles. It also hides the true shrinkage. Washing it out before cutting lets you work with the fabric as it will behave in the finished garment. If you’re dyeing, sizing creates a barrier that blocks dye from penetrating the fibers evenly, leaving you with blotchy, uneven color.
There are also comfort and health reasons. The stiff, slick feel of new sheets or clothing comes from sizing, and some people find it irritating. Beyond the sizing itself, fabric finishing chemicals can include formaldehyde resins (used for wrinkle resistance), dispersal dyes that rub off onto skin, and flame retardants. These additives are a known cause of textile contact dermatitis. Washing new fabric before wearing or using it removes or reduces these residues significantly.
Start With a Simple Hot Wash
Before reaching for any additives, try a plain hot water wash first. Set your machine to the hottest temperature the fabric can tolerate, use the longest cycle available, and select maximum agitation. This alone dissolves most CMC-based sizing completely and loosens starch and PVA sizing enough to wash them away. Skip the fabric softener, which can leave its own residue.
After washing, check the rinse water. If it still looks cloudy or feels slippery, the sizing hasn’t fully come out. Run a second cycle. Many fabrics need two or three washes to desize completely.
Methods for Stubborn Sizing
When hot water alone isn’t enough, the right booster depends on the type of sizing you’re dealing with. Since most people don’t know what sizing their fabric has, a good all-purpose starting point is a hot wash with an enzymatic detergent plus washing soda (sodium carbonate). This combination covers the most common sizing types at once.
Starch-Based Sizing
Starch sizing responds best to the enzyme amylase, which breaks starch molecules into sugars that rinse away easily. Amylase is the same enzyme in your saliva that starts digesting bread. Many enzymatic laundry detergents contain it. Use hot water and high agitation for best results. Peroxide-based (oxygen) bleach also breaks down starch sizing effectively.
PVA Sizing
PVA dissolves in water but sometimes clings stubbornly, especially on tightly woven fabrics. Hot water above 75°F helps, and the hotter the better. For particularly resistant PVA, adding a small amount of washing soda to the load speeds removal. In extreme cases, you can boil the fabric on the stovetop in a large pot of water for 15 to 30 minutes.
Acrylic Sizing on Nylon
This is the exception to the “use hot water” rule. Acrylic sizing on nylon fabrics comes out with a cold or warm wash cycle using a lye-based soap (like a traditional bar soap dissolved in the water). Hot water can set acrylic sizing rather than removing it.
Synthetic Sizing on Polyester
Water-dispersible synthetic sizes used on polyester are also susceptible to lye soap. A warm wash with a strong soap-based detergent (not a synthetic detergent) typically does the job.
The Vinegar and Baking Soda Method
For a chemical-free approach, wash the fabric in the hottest water it can handle with one cup of baking soda and no detergent. Then add a generous splash of white vinegar to the rinse cycle. The baking soda is mildly alkaline and helps break down sizing, while vinegar in the rinse neutralizes any remaining residue and softens the fabric. This works well for new bedsheets and cotton garments where you want to avoid detergent fragrances or additives.
One thing to note: don’t add the baking soda and vinegar at the same time. They neutralize each other on contact, producing water, carbon dioxide, and salt, which defeats the purpose of using either one. Baking soda goes in the wash, vinegar goes in the rinse.
Handling Delicate Fabrics
Silk, wool, and other protein-based fibers can’t handle the high heat and aggressive agitation that work so well on cotton and linen. For these fabrics, hand-wash in warm (not hot) water with a gentle soap and let the fabric soak for 20 to 30 minutes. Gently squeeze and agitate by hand, then rinse thoroughly. You may need to repeat the soak two or three times.
Avoid washing soda, lye, and oxygen bleach on silk and wool. These are alkaline products that can damage protein fibers, causing them to felt, lose their sheen, or weaken. Stick to mild soap and patience. Linen, on the other hand, tolerates heat and alkalinity well, so you can treat it the same way you’d treat cotton.
How to Tell the Sizing Is Gone
The easiest test is feel. Desized fabric is noticeably softer, more pliable, and drapes differently than it did on the bolt. It also absorbs water readily. If you drip water onto the fabric and it beads up or sits on the surface instead of soaking in, sizing is still present. For dyeing projects, this absorption test is especially important: any remaining sizing will block dye uptake in those spots.
You can also look at the wash water itself. Sizing often makes it slightly cloudy or foamy. Once the rinse water runs clear and the fabric feels soft and absorbent, you’re done. Dry the fabric according to its care instructions, and if you’re sewing, press it before cutting to account for any shrinkage that occurred during washing.