stain removal

Stain removal – Wine, Honey, Coffee or Chocolate

One of the most common problems in all chemistry and materials science: how to get rid of a stain, no matter what stain it is, we don’t want it!. From a scientific perspective, oil on the garage floor, red wine on a white rug, and chewing gum on your pants seat all present different cleaning challenges (at least until self-cleaning clothes hit the market). Today we are explaining how do stains work, and how we can use chemistry to remove them.

Ground rules

A stain depends on two factors: the contaminant and how it interacts with the material it hits. Most household stains are surface ones, where the contaminating substance flows into the gaps of a material, such as the fibers of a cloth or the pores in a concrete floor, and become trapped there.

There is another type of stain that is formed because of the molecular reaction. For example, those notorious yellow marks appear on the armpits of your white shirt because your sweat reacts with the aluminum chloride in your antiperspirant. (If you’re actually sweating yellow liquid, you have more than stains to worry about.) In other cases, a dye can form covalent bonds with a material to create visible marks, as when you tie-dye clothing. Fortunately, those stains are extremely rare and usually deliberate.

In all cases, your first step should be to pretreat the stain as quickly as possible. This means wiping up any excess spillage and then putting down something that will start to draw out the stain. For example, you could dab—never rub—at an untreated stain with a paper towel or other absorbent item, allowing capillary action to draw up the liquid. Then dampen the mark with cold water, which generally helps keep stains from setting.

At this point, once you’ve pretreated the stain, you can apply a stain remover (and, depending on the substance, even rub the mark with it). But you need to choose your cleanser wisely.

Cleaning toolkit

After you’ve pretreated the stain, you need to look at the specific substance you’re dealing with. That’s because different types of contaminants respond to different cleansers. Here are a few you should know.

The most common stain removers are surfactants. Examples include dish soap, laundry detergent, and many industrial suds. Surfactant molecules have two polar ends, one hydrophilic (or water-friendly) and one hydrophobic. These cleaners work a bit like velcro: One end attaches to a water molecule, one end attaches to a molecule of the stain, and off they swirl. However, the same reaction allows surfactants to remove dyes as well as stains from your clothes, so read the label before using this type of stain remover.

Another approach is to use oxidizers. These substances don’t remove the staining substance itself; instead, they blast the part of a molecule responsible for color, called a chromophore, with oxygen molecules. Strong oxidizers knock chromophores out completely, which is one of the reasons why you don’t put bleach in your dark loads of laundry.  You have to be careful with organic fibers like wool or silk, as some oxidizers can weaken or even dissolve them. Test weaker oxidizers on these fabrics before you deploy them on a large scale.

Also popular, especially for organic stains, are enzymatic cleaners. These use sets of enzymes to break down the molecules of the staining substance. Lipases, for example, break down lipids like olive oil. Many of these are more environmentally friendly than their harsher brethren. But these cleaners can vary widely in concentration and the type of enzymes used. In some, the labels won’t disclose which enzymes are in the mix; instead, they list an “enzymatic blend” as an ingredient. Unlike surfactants, you might have a harder time finding these stain removers in a pinch, such as when you’re traveling or away from home. To purchase this type of cleaner, check the label of a commercial stain remover for terms such as “enzymatic action,” and look closely at which types of stains it promises to treat.

Finally, for the toughest of the tough stains, you’ll need solvents like rubbing alcohol and acids like white vinegar. These harsher cleansers let you dissolve, grind off, or corrode away the tenacious color. When you do use vinegar, you’ll want to dilute its concentration with water, such as adding one part vinegar to two parts water.

Red wine stain

You may not think of your red wine as a dye, but it’s full of anthocyanins, which are common natural dyes for textiles. Even worse, when you find them in wine, they’re dissolved in alcohol and water, making your glass’s contents the perfect cocktail to ruin any cloth they touch.

When possible, use a surfactant to remove the stain on the surface. That may not be enough, so also apply an oxidizer to knock out the chromophores. For example, you might start with dish soap and follow it up with hydrogen peroxide.

Honey and other sweeteners

Syrups like these mostly consist of sugars, which love water. A little H2O should pull them out. In most cases, you can just scrape off the goo and then dab at the stain with cold water. If a mark remains, try a light surfactant as well.

Coffee stain

A coffee stain left to cool will be hard to remove. If you get a drop of coffee on your shirt, then blot it up, turn the cloth around, and run cold water through the back of the stain. This turns your clothes into a sort of reverse filter, pulling the coffee out of the material.

If you are dealing with a dried stain, at this point, all you’re really dealing with is the chromophores. So do what the coffee professionals do: Grab some sodium percarbonate. At high concentrations, this substance cleans out industrial-grade coffee machines, so a solution of ¼ cup sodium percarbonate to 2 cups water should easily destroy your stain.

Chocolate stain

Chocolate is a one-two punch. It’s both oily, so you’ll need a surfactant, and organic, since the sweet treat includes vegetable oil (such as cocoa butter) and various cocoa solids.

That means for best results, start with soap and then follow up with an enzymatic cleaner. Use plenty of cold water. Once you’ve pretreated a chocolate stain, this is one of the rare occasions where you should rub the mark to loosen it.

If you have tried everything and the stain is still in your carpet, couch or bed, call a professional!