Engineer & Entertain

Ideas I grapple with

Archive for the category “Forensics”

Science Friction

After watching “The Hot Seat Card Magic Trick” episode of Scam School I became interested in the Pilot Frixion pen. Watch the video below if you want to learn the trick in full, but what interests me is that the pen’s ink is erased by heat.

Previously I was only aware of the erasable pens which used an ink mixed with a rubber cement like material. Until the rubber cement set, the ink was erasable.

My first thought, “Could I use this pen to journal my plans of taking over the world and then throw it in a hot place to erase the evidence when the FBI raids me?”

The answer is yes, but really no. While the ink does disappear with heat from an open flame, oven, or vigorous rubbing, the content is still easily read by applying a raking light to view the impressions made by the pen.  Not to mention the FBI could use electrostatic detection to read my plans for global domination.

A raking light is applied so the impressions can be read.

Highlighting some of the impressions.

 

Furthermore, the ink reappears when the paper is chilled in a freezer. It is not as dark as when it was first written, but it is very legible. I like the idea of writing a secret message, erasing it with heat, writing a non-secret message over it, and then having the recipient freeze the letter to read the hidden message.

The original message

The message reappears after being frozen for less than a minute.

 

Microwaving the ink would require a considerable amount of time to be erased. I microwaved an index card with a message for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds. When microwaving the card, I also microwaved 1 cup (250 mL) of water. The water was there for safety reasons as I was unsure if the index card would catch fire if it was microwaved alone. The message remained intact until it was microwaved for 120 seconds. After being microwaved for a two minute duration, small portions of the message were erased. Not enough for me to recommend microwaving the message as a method of erasing it for a magic trick or removing evidence of a plan for global domination.

After microwaving for 120 seconds

After microwaving for 120 seconds.

 

The Frixion pen is useful for magicians, people who schedule their calendars with ink, and students who want to appear they live life on the edge by taking a math test in ink. Despite all of these uses I cannot recommend it for planning the crime of the century.

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