Writing with Violets: Parlour Chemistry c. 1800

As fascinating as I find dictionaries and the long s, I was worried that this blog just didn’t have enough color this week.  I decided to change that with the help of my backyard full of violets and a chemistry experiment in the guise of a party trick from about 1800.

I was inspired in part by this blog post about 17th century scientist Robert Boyle and violet syrup.  Violets contain similar pigments to litmus, a lichen-derived dye that changes color in the presence of acids and bases. I remember using litmus paper in long-ago chemistry classes, but violets? It’s true! Violet syrup and violet juice have similar properties as pH indicators and were readily available to chemists (and amateurs) of the 18th and 19th centuries, at least in spring-time.

From Select Amusements in Philosophy and Mathematics by M. L. Despiau, translated from French by C. Hutton, 1801. (Source)

This “receipt” for a spectacular color-changing ink comes from an 1801 book with the charming title Select Amusements in Philosophy and Mathematics: Proper for Agreeably Exercising the Minds of Youth.  It’s an English translation of a French book with “additions and improvements,” so it’s hard to know where this ‘amusement’ originated.  Certainly the concept of changing the color of violet juice with acidic and basic substances is much older. In any case, this same recipe was later disseminated widely in collections with titles like A Manual of Useful Knowledge and  The New Family Receipt Book as well as copycat collections of scientific amusements. Since I’ve been working on my English Roundhand handwriting, it’s the perfect amusement for me to try.

Step One: Juice the Violets

The receipt offers no information about making violet juice, so I improvised. First, I gathered a lot of violets from my backyard- I estimate about two hundred flowers(1). Then I plucked the purple petals from the flowers(2) and rubbed them on my ceramic ginger grater(3). A mortar and pestle would probably be more appropriate, if I had one. Then I squeezed the mashed violets in a small square of muslin(4) to produce a little bit of intensely purple juice(5).

With the addition of a few drops of gum arabic, my violet juice became a beautiful purple ink.

Step 2: Prepare the paper

Next, I washed one section of watercolor paper with an acid and another section with a basic substance.  The acid recommended by my receipt is “diluted spirit of vitriol,”  now known as sulfuric acid.  Not having any on hand, I tried using distilled white vinegar.  I didn’t have any basic “salt of wormwood” (aka potash) either, so I used baking soda mixed with warm water. I used a watercolor brush to lay down a generous stripe of each chemical, washing my brush carefully in between. I let the paper dry, then brushed off some baking soda that remained on the surface of the paper.

Step 3: Amaze your friends!

Time to get out the quill pen and write with violets! First, I wrote an appropriate moral maxim on a plain, untreated section of paper. Then I continued writing on the paper treated with chemicals. As promised, my purple violet juice changed colors “immediately” when it contacted the treated paper.

Look at all the pretty colors! My substitute ingredients did not give exactly the same results predicted by my receipt. Instead of a “beautiful red colour,” the vinegar turned my purple violet juice blue. It’s difficult to see in the picture (purple doesn’t show up well in digital photos), but in person the difference is more marked.  It’s much easier to see the “beautiful green colour” the violet juice took on when written over the baking soda solution.

Here’s a detail. The little pen flourish at the top crosses the boundary between plain paper and paper washed with the baking soda solution, so it’s partly purple and partly green!

I hope your mind is agreeably exercised by this philosophical amusement- I know mine is! I feel ready to deal with black-and-white topics again next week.