Hey Jim:

Q:
I cleaned a tan sofa and it turned pink after it dried! I rinsed it with an acid rinse and thought it was always safe. What happened?

A:
What you experienced is known as an “indicator dye change”. This rare occurrence is caused when the fabric's dye reacts with a cleaning solution in the same way that the dye used in litmus (pH) paper turns various colors depending on the pH of the solution that it is exposed to.

When a fabric that has such a dye used in it is rinsed with an acid rinse, it may turn pink or red just as pH paper would when dipped into an acidic solution.

Here Is A Possible Solution:
Fortunately, in most cases the solution is simple. Apply undiluted household ammonia to the fabric, and the higher (base or alkaline) pH of the ammonia will neutralize the acidic condition of the fabric that made it turn pink, and the color should revert to its original tan color. As ammonia is a gas, the pH will then revert back to neutral as the ammonia leaves the fabric and therefore the material will be residue free upon drying.

Ammonia as you purchase it in the grocery store is the best solution for this problem.  Avoid “sudsy ammonia” or cleaners that simply have ammonia as an ingredient, as such products contain detergent that may leave a sticky residue.

Unfortunately even “straight ammonia” can be of variable strength, so to be on the safe side, dilute the ammonia 50/50 with water before using it.  If the discoloration remains, re-apply it at full strength.

NOTE:
If the fabric contains dyes that might bleed, even this brief exposure of ammonia could potentially cause color bleeding!  Unfortunately, if you are already in the position of correcting this problem, you have little choice but to assume this risk.  That said, ammonia rapidly self neutralizes and is very unlikely to cause color loss when used in this fashion.