There are two reasons that this can happen.
Carpet cleaned then spot returns.
How to make sure a spot does not come back after cleaning.
Using a white cloth or towel depending on the size of the stain gently rub the area back and forth or in a circular motion so the water based cleaning mixture covers the entire stain.
Say you use a fair amount of spot cleaner to clean up your spill and finish by blotting up the tips of the carpet fiber.
This is most often a result of wicking which will be discussed below.
Vigorous scrubbing could damage your carpet or upholstery.
When spot cleaning yourself place a folded white terry cloth towel over the spot just after you clean it while the spot is still moist.
There are two primary causes of carpet re spotting.
After cleaning a spot or stain from your carpet there are times where it will return just shortly after the carpet dries.
Re soiling from various residues and soil wicking after carpet cleaning.
Either way it can be quite annoying to see spots and stains re emerge on a carpet you thought was just professionally cleaned.
These type of spots usually start out as a spill.
This is most often referred to as rapid resoiling.
At other times the spots and stains come back after the passing of a few weeks.
Now the remaining liquid will carry some of the spill back up to the carpet surface due to capillary action also called the wicking effect.
When it dries the spots and traffic areas come back.
Wicking is one of the most common result of returning spots.
The reason the spots return has to do with the mechanics of capillary action.
As carpet dries water evaporates from the tips of the carpet yarns drawing some of the remaining moisture behind it.
When the carpet is cleaned it looks good.
These returning spots can be as much of a surprise to your carpet cleaning professional as they are to you.
Another common reason for returning spots after carpet cleaning is residue in the carpet.
Do not scrub the area.
Naturally you expect your carpets to look better after carpet cleaning than before.
One originates below the carpet fibers in the backing or pad of the carpet.
The good news is that if a spot actually wicks back it can be removed.
Other times the spots come back after several weeks have passed.