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Tuesday, 7 May 2013

Childish Experiments #2

In my quest for a solvent which can remove newsprint ink from newspaper I’ve been doing a bit of online research. Whilst doing this I’ve rediscovered an activity I remember from my childhood. It wasn’t so much an experiment, more an interesting discovery, that Silly Putty (the fascinating, mouldable, semi-solid goo in a plastic egg) will pick up the text from newspaper when they are both pressed together.

So as a child I would go around collecting text and images from newspapers on my flattened Silly Putty, then squishing the putty together until the writing had gone. I’d repeat the process over and over until the olive green putty turned black from all the blended ink. I don’t remember ever wondering why the transfer of text was so successful with the putty, and yet didn’t occur when using other mouldable substances such as clay. It turns out there is a scientific reason for this. It’s all to do with the solubility of the ink.

A rule of thumb for solubility of two substances is “like dissolves like.” Polar substances (such as water or alcohol) will dissolve other polar substances. Likewise, nonpolar substances (such as oil and fat) will dissolve other nonpolar substances. However, polar and nonpolar substances (oil and water) do not dissolve in each other.
Newsprint ink is a pigment suspended in oil (a nonpolar substance) which is adsorbed by the paper. Since Silly Putty picks up the ink from the newsprint, it must also be a nonpolar material. The pigment-oil suspension of the newsprint ink is readily adsorbed by Silly Putty. Our oily skin often picks up newsprint for the same reason.

From this, I can conclude that inks which the Silly Putty cannot pick up are polar substances and therefore are not readily picked up by the nonpolar Silly Putty.
So does this then give me a clue as to how to dissolve newsprint? Nonpolar solvents, as a rule, sound pretty unpleasant to me...
At least this discovery has started me thinking about testing a greater range of solvents to discover which may share the polarity with the various inks and pigments I have been using. So far I’ve tried numerous household cleaning solutions, as well as acetone, surgical spirit and white spirit, with varying success. My next batch of experimentation will be with various inorganic salt solutions; beginning with table and Epsom salts, and then progressing away from the commonplace and further into the world of chemistry. I’m curious to see how they may react when placed side by side with a selection of pigments, inks and solvents… *dons mask and gloves*

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