How bleaches work

by Jeff Cross 

The advanced stain removal expert should be well-versed in the use of bleaches.

Cleaning can be defined as removing unwanted foreign substances.

But stain removal is often accomplished by altering the color of the stain, rendering it invisible, instead of removing it. That's where bleaches come into play.

You could compare bleaching action to rust removal - at least the final result. If you apply a strong acid to a rust stain, the rust stain remains. It's the color of the rust that is made invisible.

With bleaching stains in textiles, you are doing the same thing: Making them invisible.

Categories of bleaches

For this carpet and furniture cleaning discussion, there are two types of bleaches that are safe to use without much fear of causing damage to fibers and colors. These are:

• Oxidizing bleaches (such as hydrogen peroxide and sodium percarbonate)
• Reducing bleaches (such as sodium bisulfite, metabisulfite and hydrosulfite). 

Reducers give you the same final result, but with a different path of delivery. They remove oxygen molecules from the textile and stain, again altering the color molecule that creates the stain's color.

Oxidizers work best of organic stains (natural). To remember this, repeat to yourself five times "oxidize the organics" and you will never forget.

Reducing agents work best on synthetic stains (manmade). To remember this, repeat to yourself five times "reduce what's not real" and you will never forget.

This doesn't mean you can't cross over the line. Often, oxidizers will remove the last vestiges of a synthetic stain, and vice versa.

Putting them to work

Stain identification is job #1. Since each type of bleach has an affinity for either natural or synthetic stains, you need to make the proper match.

Purchase your bleach from a qualified formulator. These bleaches typically have a "lubricator" in them, a chemical to speed penetration of the bleach into the fiber.

Don't worry at this point about how much to use, or the dilution. Those directions will come from your chemical supplier.

Adding a small amount of alkaline (such as ammonia) to an oxidizer makes it work faster. Alkalines accelerate oxidizing bleaches.

Adding a small amount of acid (such as acetic acid) to a reducing agent makes it work faster. Acids accelerate reducing agents.

Remember that natural fibers like wool or cotton are sensitive to many types of chemistry. Using sodium percarbonate with its natural high alkalinity is not recommended on these fiber types. Same with stain resistant nylon fibers. Liquid peroxide with a more neutral pH is better.

Acceleration, delivery and safety

As with most classes of cleaning chemistry, adding heat makes both classes of bleaches work faster. But with active chemicals, the reaction speeds up, so watch that reaction carefully to avoid unwanted color loss (from the textile's original color).

Apply your bleach from a flip-top bottle, spray bottle or your preferred method of delivery.

Caution: If you enclose an oxidizer after mixing with an alkaline, the chemical will off-gas and eventually find its way out of the bottle, perhaps via explosion. It won't be pretty.

You can let the bleach work on the fabric for several minutes up to several hours, or you can use a damp towel and an iron to accelerate reaction. A safer heating method is steam from a portable steamer.

Another way to accelerate an oxidizer is to use an ultraviolet light (black light). This type of light reacts with the chemical and speeds the bleaching. It is safer to use light acceleration than heat acceleration.

After applying the bleach, warming or heating the stained area, keep an eye on the reaction. Some of the stain may be transferred into the towel, which may be part of the physical removal but not the ultimate action you are looking for.

To stop the bleaching action if you see unwanted results, you can flush the chemical out of the fabric. But to quickly  stop an oxidizer, add a reducer and then flush, and vice versa to stop a reducing bleach action.

Oxidizers are more "dangerous" to original colors, especially using an iron.

Reducers are less aggressive to natural colors, but tend to be much faster than oxidizers in the stain removal process.

Remember: What you are trying to achieve is the alteration of the color molecule. Even if you can't alter the color so it is completely invisible, often the remnants of the stain are removable with continued cleaning.

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