If you want really white fabric, be it white towels or white shirts, you need bleach, right? Not so fast. There’s a very old laundry additive that uses a bit of magic to get many fabrics whiter than bleach could ever hope to.
Laundry bluing, as you might have already surmised, is literally blue. It’s a type of blue dye that you add to a load of white laundry to make the white laundry appear whiter.
The bluing isn’t for lightly used fabrics that still have their original crisp white color but is instead intended for more heavily used fabrics that have taken on a yellowish-gray color cast with time. If you used it with brand new white shirts, you’d end up with white shirts sporting a blue tint.
When you add it to older and slightly yellowed fabric, however, thanks to the subtractive color model of color perception, the blue and the yellow coloration cancel out, and the fabric looks whiter. In most cases, this works far better than bleach as bleach can yellow some fabrics, accelerating the very thing you’re trying to undo.
The concept of bluing has been around for centuries—it’s one of the old school cleaning tips we highlighted here—and you can still buy Mrs. Stewart’s Concentrated Liquid Bluing, a Victorian-era laundry bluing agent, at your local store or right off Amazon.