Many carpet cleaning technicians have run into this problem: You clean a soiled, spotted carpet.  All looks fine when you leave and then a few days later, spots not only return, they're even bigger. Soon, you are called back to remove the spot and after sighing in frustration, it's time to understand what likely happened.  

As to a spot going from the size of a penny to a salad plate, "this is often caused because the spill [or soiling] has drifted deep down into the carpet fibers, even as far down as the backing," says Doug Berjer, eastern division sales manager for CFR (continuous flow recycling) extractors. "If not thoroughly removed, it wicks back to the carpet's surface and spreads."

Other reasons, he adds, spots don't die after cleaning include:
• Not using the correct spotter

• Using too little spotter

• Not carefully rinsing out chemical residue after spotting or extraction (which can attract more soil)

• Not using air movers; "air movers can reduce the amount of time the spot needs to wick back up to the surface," says Berjer.  
To help prevent these call backs from happening, Berjer suggests:
• Examine the spot carefully.  An experienced technician usually develops an eye for problem spots and knows to spend more time and effort removing them. 

• Make sure the right spotter is used, mixed per manufacturer's instructions, and followed by a thorough rinsing.

• An encapsulation rinse can help; crystals encapsulate the spots, which are then removed with vacuuming.

• Apply anti-soiling treatments to the problem areas; they attract residues that are later vacuumed away.

• After extraction, make a poultice by layering towels over the spot, covering with a weight.  As the carpet dries, the residue will transfer to the towel.
"Possibly the most effective way to remove spots is to use top-notch equipment, including the wand," adds Berjer. "Some atomize water/cleaning solution to more effectively remove all soils, including problem spots."