ICS Magazine

Spot and Stain Identification

October 12, 2004
Your spot/stain investigation probably won’t be this extreme.


Probably the biggest challenge for professional carpet-cleaning technicians is addressing the unknown spot or stain.

The factors that must be considered in determining the cause of the spot or stain include size, shape, color, feel, location, taste, pH, smell, and history. Keep in mind the old adage that "A blind man can find a spot but he can't find a stain." A spot is caused by material attaching to the yarn that you will be able to feel, but a stain is caused by a color-changing substance that penetrates the yarn, and it won't be apparent to the touch.

Determining the source and makeup of unknown stains and spots often involves a certain degree of detective work, including asking lots of questions and usually believing only a small percentage of the answers. Not that all end-users are liars, but there is a tendency for them to color their replies to make them seem less responsible for any permanent problems with the stains and spots. So, we use the senses we are blessed with to come up with a diagnosis of the cause of the spot or stain and, possibly, the solution.

Size may provide a few clues as to the source of the problem. For instance, all of those quarter-size spots near the dining room table could be the result of dropped or dripped food or beverages. The dime-sized spots near the coffee or beverage machines or under the desks in the offices are probably coffee or drink drips. The big spot about the size of a dinner plate may be the result of a spilled cup of a sugary beverage which was not cleaned up properly and is binding soil to the sugars or the spotting agents remaining in the carpet.

The shape of the spot or stain will provide some clues to the mystery. If the spot or stain is perfectly geometric in shape, it may well be a color-loss condition resulting from a table, desk, box, rug, or pot sitting on the carpet. A spill will generally be irregular in shape with "fingers" extending from the main spill body. A spill stain that is somewhat oval-shaped may be the result of detergent residues left from previous cleanup attempts (think of the "wiping" pattern often used when cleaning up larger spills).

Color may be an indicator of the cause of the spot or stain. Red would be a pretty good indicator of spilled beverage, such as soda or red wine. Yellow spots may be the result of urine contamination, pH discoloration on a white stain-resistant carpet, or the presence of a bleaching agent. Blue spots are perhaps from spilling a blue beverage. Dark brown to black may just be soil built up on the carpet surface as a result of spotter residues.

Get in touch with your work. Spread the yarns to see what colors are present under the surface of the carpet. Feeling the spot may provide some clues to its source. We are pretty familiar with the feel of wax or chewing gum, so touching either of those will tell you rather quickly what you are dealing with. Sugary residues, such as from a soft drink, will be a little hard and sticky.

Where the discoloration is located may tell you what it is. A spot or stain near the break areas in an office or near the kitchen and dining areas in a home would probably be food or beverages, while a spot or stain near an outside door in an office or home may be the result of tracked-in grease, oil, or mud from outside.

The pH of a spot or stain is easily checked with a pH pen or pH paper or tape. Moisten the problem area slightly with distilled water and apply pen or tape to determine the pH. Check the pH against any commercially available pH chart to get a better idea of the cause and the correct spotting agent to use to remedy the situation.

Out of deference to your nasal membranes, smell may not be your most widely used sense in determining the cause of your spot or stain, but it will definitely identify some staining materials and rule out others. Techniques may vary, but a common approach is to stick one's nose in the spot and breathe deeply. I prefer to rub the spot with a slightly damp towel and then smell the towel (it just looks a little more professional to me). A little dampness on the towel makes the smell a little more apparent.

The ears make a good source of information relative to the spot or stain. Listen to the end-user's history of the area. He or she may or may not be able to tell you exactly what has been used on the spot in prior cleaning attempts. Just don't expect your client to be totally candid with you about what they have used, especially in color-loss or color-added situations.

If your testing indicates that grease or oil is the culprit, begin spot treatments with a volatile dry spotter first. Volatile spotters cannot penetrate yarns that are wet from water. If you determine that the problem is caused by a wet side product, including spotting-agent residues, begin your treatments with a thorough freshwater rinse to bring the fiber or yarn back to a "clean" state. Many times, do-it-yourselfers apply lots of spotting agents but don't rinse, so the spot may be loose but in need of a good rinse. So get the fiber or yarn as clean as possible with plain water and have at it with your spotting agents. And perhaps a silent prayer to the spotting gods.

Last but not least, taste. I was just kidding about taste. See ya next month!