Ask A Scientist© Chemistry Archive

name         Debra M.
status       other
age          30s

Question -   What makes ink stains difficult to remove with regular
stain removers?
What happens between the ink and fabric? My daughter has asked this

Question- a project for school- we have tested many liquids and are able
to remove many with stain removers, but ink is one of the darker stains
that persist.Why?
--------------------

Debra,

Stains can (sometimes) be removed by application of one or more of about
three approaches.

1.  Sometimes the colored (stain) molecules can simply be dissolved in and
suspended within micelles of water and soap or detergent (... you can look up
the definition of a micelle in a dictionary or science encyclopedia on the
net) and then rinsed away with lots of clean water. This is the traditional
washing machine approach.

2.  Sometimes the stain molecules can be cut (oxidized) into smaller
molecular fragments that are less colorful or even colorless by the action of
a bleach or enzyme in the laundry product. This often happens when
enzyme-fortified laundry products go to work on grass stains and blood. Then
the process described above can be used to remove the residues.

3.  Some stains cannot be dissolved and suspended in water even when
fortified with soap or detergent. However, they might be soluble (and thereby
removable) by the effects of cleaning fluid solvents such as those used by
dry-cleaners.

Inks sometimes contain oxidation-resistant and/or particulate colored
substances that bind tenaciously to fabrics and can be difficult to nearly
impossible to remove. For example: The ink in laundry marking pens and the
stuff referred to as "India ink" are suspensions of carbon black (sorta like
soot) in a liquid. Once applied to the fabric, the carbon black soaks into
the pores of the fabric where it tightly binds to the fibers. Since the
carbon black is not attacked by enzymes, is resistant to oxidative attack by
bleach, and is not emulsifiable by soap and water, it is all but permanent.
Thus the term, "permanent marker." Some artists' inks contain colored
particulates. These inks can be distinguished from simple dye solutions
because they are not clear. Rather, they look a little cloudy.

I hope this is of assistance.

Regards,
ProfHoff
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This is an "iceberg question" -- that is only about 10% of the question is
apparent and the rest lies hidden beneath the surface. First of all, it
depends on the type of ink, the type of fabric, and the type of remover.

Water based highlighter ink for example is pretty easily removed with soap
and water, where "permanent" black markers are difficult in the best of
cases.
The reason for the difference is that the ink is intentionally formulated to
do different jobs, and, as you have observed, they do!!

Different fabrics are more or less receptive to staining. At one end of the
spectrum it may be almost impossible to remove a stain from a fine linen
lace, and quite easy to remove the same stain from a nylon carpet. The
reason is that these and other fabrics are designed with stain repellency in
mind. Carpet makers know things are going to be spilled on carpets and
design the fabrics accordingly. Hand made lace is not designed to withstand
staining.

Stain removers are not all created equal. Some are a mixture of aqueous
surfactants [soaps] and mild solvents [rubbing alcohol]. These are fairly
kind to fabric but aren't very effective against things like permanent
marker, or even some ball point pen inks. Other stain removers contain
stronger solvents like nail polish remover, and other "industrial solvents".
Safety and the need to be gentle to the fabric limits what solvents can be
put into a consumer-type product, however.

Some stains can be "removed" by bleaching rather than dissolving the stain,
while other stains are impervious to bleach.

Yet other types of stains actually attack the fabric, and these may never be
able to be completely removed.

There is a whole chemical technology behind "stain removal" and the bottom
line is really tough stains should be left to a dry cleaning establishment
who has more powerful industrial stain removers and the knowledge about
which one(s) to use.
Vince Calder
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