What are Laundry Sizing and Laundry Starch?

A man applying laundry sizing
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If you love the feel of a crisp, but not stiff, shirt or pair of slacks, then you need some laundry sizing and a clothes iron. Yes, you're going to have to iron!

Definition of Laundry Sizing for Ironing

Sizing is a resinous solution that adds body to fabric, creates soil resistance when the garment is worn, ease of soil removal when the fabric is washed and makes ironing easier. The sizing solution can be vegetable or petroleum based. It is often applied by the textile manufacturer during weaving or knitting or by the clothing manufacturer during construction of garments. Some textile companies use formaldehyde as a fabric sizer, which is another good reason to launder all new clothes before wearing.

Laundry sizing or fabric finishes are also available in aerosol and trigger spray bottles for home use. They can be purchased in most mass markets or online from Amazon.

Sizing is the preferred method of adding body and crispness to clothes made of human-made fibers such as polyester or cotton/polyester blends because vegetable-based starch will not adhere to these fibers. It can be used with the lower ironing temperatures recommended for these fabrics.

Sizing can be used for natural fabrics like cotton and linen that must be ironed at higher temperatures, but it is not as effective as starch for adding stiffness.

Definition of Laundry Starch for Ironing

Laundry starch is made from rice, corn or wheat. The use of starch adds body to fabrics, creates soil resistance and easier soil removal and makes ironing easier. As a natural product, starch works best on 100% cotton, cotton blends, and linen if you want crispness.

Starch can be purchased in aerosol cans, liquid or powdered form. You can even make it at home. For the straight-from-the-cleaner crispness, you need to use a liquid starch because the entire shirt needs to be dipped.

In addition to its usefulness as an ironing aid for clothes, Sta-Flo Liquid Starch can be used to create kid's crafts like paint or paper mache paste. One of my favorite ways to use liquid is to shape and stiffen crocheted crafts. The handiwork will hold its shape forever, as long as it stays dry.

Laundry Sizing vs. Laundry Starch

If you are looking for stiff collars and cuffs on a natural fiber fabric like cotton, linen or bamboo, use starch. Starch is made from wheat, corn or rice and can be mixed in concentrations that will completely stiffen natural fabrics.

If you want only a slight crispness and a smoother, sharper looked to any fabric - natural or man-made - after ironing, use sizing.

Sizing does not discolor fabrics and is safe to use on all washable fabrics. It is so light that scorching or gumming up an iron plate is less likely than with starch.

Spray sizing is removed from the fabric after each washing and should be reapplied at the time of each ironing.

How to Use Laundry Sizing for Ironing

While starch can be applied to fabrics and allowed to dry before ironing, you will have better results with sizing if you spray small areas of the garment just before ironing. Hold the sizing can or bottle about eight to ten inches away from the fabric and spray with light even coating.

Iron the area following the recommended iron temperature setting for the fabric type. Then move to the next area. Allow the ironed garment to cool and dry completely before wearing or storing to avoid excessive wrinkling.

Other Uses of the Term Sizing

  • A form of sizing is used during the manufacturing of paper to reduce liquid absorbency. The addition of sizing allows inks and paints to remain on the surface of the paper rather than being absorbed. This is particularly important when printing wallpaper, art and reading materials.
  • The term sizing is also used for any surface to which gilding or gold leaf will be added. This sizing of the wood, plaster or paper allows the gold leaf to adhere to the desired surface more quickly.
  • In weaving, sizing is the term that is applied to the warp yarn on a loom and is essential to reduce breakage by improving the strength and abrasion resistance of the yarn. Size can be made from starch, oil, wax, gelatin or manufactured polymers.