Here we go with Halloween 2016! Usually there are many Halloween projects in motion all year with nothing ready to display until October, but I’m so happy that this year I have a COMPLETED new project already finished, even before September began! These underlighted test tube racks for your spooky Halloween laboratory will make your test tubes glow, can use any color bulbs you like, and have no power cords to hide!
I invested in around 100 plastic test tubes with matching lids for the Exploring Ectoplasm Essences tasting quiz for Halloween 2014, so of course I want to use them again! Those tubes were intended to be displayed in the round distillers in the Ectoplasm Engine of the Spirit Materializer device, but the Library Laboratory needs a more traditional and authentic way to hold many test tubes, plus we need a better disposal plan for the used tubes. Halloween 
guest Elisabeth worked in a college chemistry department and found me an old wooden test tube rack from the trash that was perfect so I thought I’d make more to match from scratch, then I finally stumbled on brand-new ones that matched on Amazon where I could use free credit card points!
I found these LED battery string lights had the smallest battery packs on Amazon (sure wish I had found them for my Elsa sparkling snowflake cape!), plus the bulbs were inline along thin copper wire that was easy to bend into whatever shape necessary. They sell several colors, but the purple is not UV reactive enough for black light effects.
My test tubes were a little skinny for these wooden racks, but it’s not enough of a problem for me to rebuy test tubes, since the curved divot in the base still holds them from sliding around too much. If that is a concern for you, you can purchase fatter test tubes to go in your racks, or I have seen some sets of racks that come with test tubes in Halloween decor this season. My test tubes still sat in the center of the divots, which is what is important, since that’s where you hide the light. I marked spacing of the centers of the divots from one end on some scratch paper, then turned that over to transfer the marks and then drill from the bottom side. If you have an extra long drill bit, you may be able to drill through the top holes to aim for center without measuring, but you can see mine didn’t reach far enough to go all the way through the wood. Make sure you use a drill bit large enough to fit 2-3 of the LEDs into the same hole.
Leave the drilled rack upside-down to add 2-3 bulbs into each hole, sticking up as far as they can without the bulb actually peeking above the wood into the curved divot. Use your fingers to feel if they are poking out at all. I found it was easiest to twist 3 bulbs together along the wire starting at the battery pack. If you are using the shorter test tube racks, you will have leftover lights, but these copper wire strings are easy to cut off the bulbs you won’t use, and the rest of the string stays lit.
As you shove the bulbs into the holes, bend the wires as flat as possible against the wood to the side, compact so none peek out past the wood. The wires will not bend flat enough for the flat wood base to sit on the wires without rocking, plus this thin battery pack can tuck under the rack to hide it as long as you add wooden bead feet…however the glow escapes out the bottom too! I was able to use a single width of heavy-duty black duct tape that covered the light spill plus neatened the wire mess, but you have to cram the wires tightly together or they will sneak out of the tape edges. You can see in the photo to the right that I have one rack showing the bare wires folded, then one already taped down before adding the wooden bead feet with hot glue.
The wooden feet only prop up the racks a little, but enough to see the bright white battery pack at the wrong angle, so I made a hinged flap from the same black duct tape that has enough sticky spot to stay closed, but the edge of the tape is folded so it’s a handle to lift the battery pack to change the batteries. Make sure to orient the battery pack so the on/off switch is to the end of the rack so you can flip the switch by feel, and don’t tape it upside-down so you can’t access the battery compartment.
I was hoping for UV blacklight effects from some purple/UV LEDs, but I have discovered this summer that it is very tricky to find true UV LEDs for sale to consumers, mostly because no one advertises what the output wavelengths actually are. You can see here that using the purple version of the same battery copper-wire light string didn’t even light up the tonic water that gives a bright blue glow under even a basic compact fluorescent blacklight bulb. Even trying a 12V LED strip with good blacklight reviews didn’t make the test tube blacklight effects any better. Online research and my own testing revealed that you need the UV range to reach past 365nm for blacklight effects to show, and if it has too much range higher into the visible spectrum, you’ll just get too much purple vs. UV, exactly what happened here. If you look carefully at the very bottom of the tubes, you can see a tiny blue glow from tonic in tube 2 and a slightly green glow from the vitamin B in tube 5, but not enough to bother. What matters the most no matter what color light is how many suspended particles are in the liquid for the light to bounce all the way up the tube, without being too opaque like fruit juices. Here you can see the comparison with purple lights on the left, white lights in the back, and green lights to the right, all using the same test liquids…and our overwhelming winner for Ectoplasm Experiments to match green glowsticks was pale green lemon-lime Gatorade on the far right!
From left to right in each rack to compare:
sour apple mixer = green, glows green
tonic water = clear, should glow light blue but I don’t think there’s enough UV
different vitamin B pill = pink, glows brighter pink in UV
100% vitamin B solution = brown-green, should glow bright yellow-green in UV
tonic water + vitamin B solution = pale brown-green, should glow aqua in UV
lemon-lime Gatorade = doesn’t glow in UV from any vitamin B, but refracts light perfectly!
Since the wooden bead feet match plus the rest of the equipment will be dark, I think I like the racks the pale natural wood color they already are, but when I get the rest of the Library Laboratory arranged, I reserve the right to decide to stain them darker….but for now, onward to other Halloween projects for the Webmistress Hosts a Victorian Halloween at Castle Brittahytta!