The technical reason is that bht butylhydroxyltoluene which is a preservative used on the backs of many area rugs will let out the bht gas.
Carpet yellowing after cleaning.
O ccasionally a brownish discoloration appears on a carpet or rug after it has been cleaned.
Spread kitty litter over the carpet.
You need a low ph acid cleaner of about 2 0 to safely remove the brown discoloration from your carpet.
If the spots are dry skip this step and move on to step 3.
This is basically a reaction that your carpet has all the time if it has butylhydroxyltoluene or bht in the carpet padding or glue.
When stain resist carpet came into existence many yellowing discolorations appeared especially after cleaning.
This in turn causes the fibers of the carpet to turn that yellowish or tan color.
Place one or two dehumidifiers in the room.
It was traced back to the cushion and pressure from the mills put an end to it.
The kind of yellowing is noticeable because it is a very bright canary or legal pad yellow.
You can reverse this by having the carpets cleaned professionally.
The gas gets trapped under the rug instead of dissipating into the air.
Pour borax over the smelly areas and with the use of a dry brush or a soft broom scrub it in the carpet.
The bht is fine as long as it has a way to air out.
One of the causes of this discoloration is a condition called cellulosic browning.
The carpet cleaner pitch to consumers of on site stain resist treatment is simply a hyped sales gimmick to.
Another possibility is that the owner has been using some type of high ph spot remover which could turn the carpet a brownish tinge after cleaning especially with a high ph traffic lane cleaner being used.
If the discoloration is still present but to a lesser degree shampoo the area a second time.
This is very prevalent with rubber backed rugs.
The other affect that you might see is called phenolic yellowing.
Professional carpet cleaners have access to equipment and cleaning solutions that the public does not.
If you found yellow streaks on your rug after cleaning there s no need to fret.
Application of after market stain resisters in the hands of the carpet cleaner will still cause yellowing or browning.
In order for this discoloration to develop several factors must be present a cellulosic fiber moisture and slow drying.
Carpet can turn yellow from normal stains chemical stains or phenolic yellowing.
Step 4 hire a professional carpet cleaner if the discolored area of carpet remains after shampooing.