Light Pen and Glow Book

Bedtime is tricky for our little ones.  They like to look at books, but I don't want to leave the light on.  If they have a flashlight, they'll leave that on all night and use up the batteries.

I've seen books that glow in the dark, but it's a pain to hold them open to every page and let the glow powder charge in the light before letting them have the book in the dark.


I wanted a book that had glowing elements, along with a light that only lights up when you press the tip against the page.  I didn't find any, so I made them myself.  I used a book we already had, Goodnight Moon, because Benjamin and Lilith already love it (and we have more than one copy).


I didn't feel like buying anything, so I used things we already had.  For the pen, I used:

large syringe (you can use some other tube that fits the batteries)
2 AA batteries
1 white LED from an old string of holiday lights (I would've used a UV led but I accidentally burned the last two out yesterday; it would've worked so much better than plain white, because it'd make the glow powder go crazy)
hookup wire
hot glue
solder (along with a soldering iron)
a small spring (something non conductive like plastic would work better than metal here; I had to coat mine in hot glue)
red felt (because the syringe was much larger than the batteries)


For the glow book, I used:

board book
epoxy
strontium aluminate glow powder (this is the good stuff; other cheaper glow powder doesn't work as well.  you'll want something really reactive like this so that the book glows nicely after just a little bit of time under the glow pen)
toothpick
parchment paper, or something else you can mix the epoxy on and then throw away
piece of a straw cut at an angle to scoop up the glow powder

I used a spring because I wanted the LED to only turn on when the tip was pressed.


LEDs have a positive and negative wire.  The longer one is usually positive (unless someone snipped it).  I soldered a wire to the positive end of the LED.  First I burned off the plastic coating at the end of a red hookup wire, pulling off the black char and exposing the wire.  Then I twisted that wire into the positive wire of the LED.

I heated up the butane soldering iron, then touched it to the twisted wires to heat them up.  The solder I used already has a rosin core, so I didn't worry about using flux.  Flux is something that helps solder stick and flow where it's supposed to.  When the wires were hot (it takes a couple seconds), I touched the end of the solder to the twisted wires.  It melted and flowed into the gaps, solidifying and strengthening the connection between the two wires.

That, in a nutshell, is soldering.  It's gluing something using conductive metal glue.

After the wire was attached, I wanted to insulate it to make sure it wouldn't short.  I used hot glue from a glue gun to cover the exposed metal on that side.

I then soldered a short, stronger piece of metal (actually a folded bit of wire) to the negative side of the LED.  I also glued a spring to the LED, making sure to cover both ends of the wire with hot glue because I didn't want the spring to conduct anything.  The piece of metal was shorter than the spring at rest; it's longer than the spring when the spring is compressed.  This is so you can press the LED, compress the spring, and allow the metal to touch the battery.  That will complete the circuit and allow the LED to turn on.

Once I was satisfied with the position of the spring and the metal connecting to the negative side of the LED, I got the batteries to test out the circuit.  I lined two AA batteries up with the negative side toward the LED and the positive side away.  The end of the wire connecting to the positive side of the LED was touching the positive end of one battery.  I was able to press the LED and spring closer to the batteries, completing the circuit and lighting the LED.

Once I knew my circuit worked, I needed some sort of case for the pen.  I was going to use an old marker, but it had some plastic structures inside that made it difficult to fit everything inside and see what was going on.

I ended up using one of Abigail's old syringes.  I cut off the tip so the LED could poke out while the spring was still inside.  The batteries were much smaller than the syringe, so I got a piece of thick red wool felt to wrap around them and keep them from rattling around inside the syringe.

I rolled the LED circuit with the batteries and wire inside the wool, then slid the wool into the empty syringe.

I pulled off the rubber part of the syringe plunger and used that as a cap at the open end of the syringe.  I pressed it in just far enough so the LED would turn on if you pressed it, but not far enough that the LED stayed on constantly.

I added some hot glue to the LED and to the tip of the syringe (making sure not to glue them together) in order to soften them and keep from scratching the book.

Use a board book for this; the pages are stiff enough to hold up to the epoxy.  I don't recommend using some other type of glue that might flake or chip off.

Only mix a tiny amount of epoxy at a time; I mixed up way too much.  You'll only be able to paint one open page at a time, so only mix up enough epoxy for that.  Using a snipped bit of straw, scoop a little bit of glow powder and mix it into the epoxy; you can use almost as much powder as you have epoxy; don't go overboard or your epoxy will be too powdery.  A little goes a long way with the good glow powder.

Using a toothpick or some tiny disposable brush, paint the glow powder mixture onto the pictures of the board book that you'd like to glow.  Maybe you'll want to outline the pictures, or color in the light spots, trace the words, put stars in the sky, etc.

Depending on the time your epoxy takes to set up, you might want to hurry.  Epoxy gets sticky and thick as it sets up, and your painting will become less precise.

Let the book sit open until the epoxy is completely cured before painting another open page.  You'll have to mix up a new batch of epoxy and glow powder each time you open a new page.

Once the book is completely cured, show your kids how the glow pen works.  It should only light up when the tip is pressed, either by a little finger, or against the page of a board book.

It's a good idea to read the story to your kids before the lights are off, especially if you didn't trace the words with glow powder.  Once you're done, they should enjoy looking at the book again with the lights off and the light pen, seeing which pictures glow.


Thanks for reading!  Please post pictures if you make your own.  I'd love to see them.