Lighter fluid removes ink because it dissolves bonds the chemicals in ink formed to each other and to the inked surface. Lighter fluid is a solvent--a substance used to dissolve another substance. Solvents may be water-based or oil-based; lighter fluid is oil-based. Substances that do not dissolve in water, such as permanent ink, need to be removed using an oil-based solvent.
Surface Prep Helps Remove Ink
Washing the ink-stained surface with warm water and dish soap breaks the attachments between ink molecules as well as between ink and the object it adhered to. Because dish soap dissolves oils, it allows ink particles to break away from each other and the stained object and go into water solution.
The less surface prep with dish soap you do, the stronger the ink will be bonded to the stained object and other ink particles. Lighter fluid by itself may not dissolve ink bonds to other ink particles or the stained object enough to allow stain removal.
Evaporation and Capillary Action
MSN Encarta defines "evaporation" as the process occurring when a substance changes from liquid to vapour. "Capillary action" is defined as the force that causes a liquid to rise, fall or change shape because of differing strengths of attraction between liquid molecules and a solid.
When lighter fluid evaporates, its liquid molecules are drawn rapidly upward into the air. That process creates capillary action as fast-moving lighter fluid molecules attract liquefied ink particles. The attraction causes ink to rise to the top of the solid, where it can be pulled into any absorbent covering placed on the solid‘s surface. Paper towels and cornstarch powder are good disposable absorbent coverings.
Lighter Fluid's Ink-Removing Properties
Lighter fluid is a liquid composed of petroleum products similar to gas that evaporate and burn easily. According to chemist Bob Atkins, lighter fluid is a mixture of hydrogen and carbon molecules that dissolves non-polar (oil-based) compounds, such as ink and grease.
Like Dissolves Like
The chemistry rule of thumb "like dissolves like" states that weak bonds are formed between similar substances, such as hydrocarbons in lighter fluid and ink molecules containing hydrogen and carbon. This principle states that because lighter fluid is oil-based, it can dissolve oil-based inks.
According to the "like dissolves like" principle, oil-based dish soap works by disrupting bonds oil-based ink forms with other ink molecules and with the stained object. Then capillary action combines forces with weak attractive bonds oil-based lighter fluid creates with dissolved ink oils to move liquefied ink away from the stained object and into a cover material you can easily discard.
Because ink bonds more strongly to other ink molecules than to evaporating lighter fluid, lighter fluid is released into the air and the ink stain is left on the covering paper towel or cornflour for you to discard or vacuum up.
Alternatives for Ink Removal
Lighter fluid vapours are invisible, highly flammable, harmful or fatal when inhaled, and may not disperse quickly. Safer alternatives than lighter fluid exist for ink removal.
Spraying ink stains with hairspray or applying vegetable oil, then rinsing with warm water and dish soap is an alternative method for removal. Chemist Bob Atkins suggests methanol or ethanol as alternative solvents. He adds acetone as another alternative to lighter fluid for dissolving organic (carbon-based) inks but warns that acetone also dissolves paint and many plastics.