One day I was perusing the internet and stumbled upon a video; Water Light Graffiti by Antonin Fourneau, created in the Digitalarti Artlab. When water is painted, sprayed or sponged on LEDs light up. This seemed like such a cool project, I was inspired to try to make my own; cheaper, easier, desktop version.

They way this works is that the one lead of the LED is separated from the power by a small gap. When you apply water, water forms a bridge that closes the circuit and lights the LEDs.

On their web page there is a link to another video where the artist discusses the process and prototypes he went through for this installation, however the video is in french (unfortunately, I didn't understand a word of the video). I did however watch what he was doing and it seems like the working prototype was made using a printed circuit board, though one of the early prototypes was made with copper tape, which fit much better with my plan to make a cheap and easy version.

For my version, the materials were acquired inexpensively, from a dollar store and the LEDs and copper tape from Ebay. It is easy enough that you don't even need any special skills or equiptment and you don't even need to solder anything.

In one article I read about the Water Light Graffiti installation drew similarities between it and Buddha Boards upon which you can draw on with water and once the water evaporates the image fades. So I modelled my project after a desktop Buddha Board.

Step 1: What You Will Need

Materials:

Artist canvas 6x9in -dollar store (cost ~$1)
Wood photo stand -dollar store (cost ~$1)
Paint brush -dollar store (cost ~$1.50)
Dish for water (check in your kitchen cupboards) (-free)

Electronics:

Copper tape 3inx1m -must be double conductive (has conductive adhesive)(cost ~$5)
40x 5mm LEDs (I used a mixture of white and RGB colour changing - should have same voltage) (cost ~$1)
Power supply -battery holder or AC adapter or wall charger, should have higher voltage than LED (I had one lying around)

Tools:

Utility knife
Scissors
Pliers
Drill
My template (see below)
(Optional): soldering iron

(Overall cost ~$10 cdn)

Front and back template.pdf
Download

Step 2: Test

So I wanted to test this out first. I used a 3v button cell, a RGB LED and used water on the tip of a paint brush - it worked quite well.

For the project I ended up using a 5.1V wall charger from an old cell phone. I mistakenly though I would need to use resistors, (3v LEDs, 5.1V power equals 120ohm resistors) I didn't factor in that the water has enough resistance itself. Unfortunately, I didn't figure this out until I went all the way through to step 8 and my LED canvas wasn't working as my test one had done. So I pulled out all of the resistors and now it works fine (though it is a bit messy and I had to solder the leads to the copper tape because I couldn't pull the tape off the back).

Some quick tips about LEDs

Just a quick word about LEDs, if you don't have much experience with them, the longer lead is positive (which would hook up to the positive end of a battery) and the shorter lead one is negative. The voltage can vary with the colour of the LED, when you buy them you are usually given that information (for example white and blue is about 3V, red and green is about 2V). If you are connecting LEDs in an array they should be about the same voltage. I used white ones that where 3V and RGB colour changing ones that where about 3.1V and that worked fine.

Step 3: Prepare Copper Tape

Cut copper tape to fit the canvas, make sure that one of the pieces of tape is long enough to wrap around to the back
With masking tape, tape the pieces of copper tape together, they should be overlapping slightly
Again with masking tape, tape the template to the front of the copper tape

-Unfortunately, the copper tape I ordered came folded in an envelope so there are wrinkles where it was folded which I can't remove, so when you tape it onto the canvas it doesn't look as nice as I hoped. If you pay more you could by the tape in rolls so you wouldn't have this problem.

Step 4: Cutting Circles

Using the utility knife cut out each of the circles
Keep track of where each of the circles came from, (I just labelled the back of each circle with a number)
Repeat (yeah, this part can be pretty tedious -I wonder if a laser cutter or a Silhouette paper cutter would work with copper tape)

Step 5: Trimming the Circles

Once all of the circles are cut, tape the copper to the canvas, don't remove the backing from the part that wraps around to the back. Try to smooth it out as best you can -this part can be kind of tricky.
Now take those circles you cut out and trim approximately 1mm off the edge of each one
Punch a hole in the centre of each circle (don't stick it onto the canvas yet).

Step 6: Drilling Holes and Preparing LEDs

Mark on the canvas where the hole of each circle is with a pencil and drill a hole on the spot for the negative lead of the LED to pass through to the back
Now take your LED and bend the positive lead 90 degrees at the notch
Then curve that lead into a circle, the circle should lie flat on the canvas when you stick the negative lead through the hole you drilled
Repeat with each LED

Step 7: Adding LEDs

Stick the negative lead through the hole you drilled, the bent lead should lie flat on the canvas
Remove the backing from the corresponding circle (you number them, right?)
Stick the circle onto the canvas, fitting the LED through the hole, smooth the tape flat.
Repeat with the rest, check that the circles are not touching the outer copper tape, if so then trim with a utility knife (you don't want them to touch -if they do still touch when you turn the power on it could blow out the LED)
Once all of the LEDs have been added, flip the canvas over and bend the negative leads so that the lie flat against the canvas back, they should all face the same direction.

Step 8: The Back

This is the part that I did wrong initially by adding resistors. I ended up having to solder the negative leads to the copper tape strips since I couldn't peal of the tape without ripping (I didn't have any extra). So if you do it the right way, which I will describe below, you won't need to solder. Use the template as a guide.

Cut your remaining copper tape into narrow strips, you should have enough tape left to finish this task
You will need 8 short strips that fit the height of the canvas and two long strips that fit the width
Tape vertically to connect the columns of leads, with the 8 short strips
Connect all of the tape columns at the top and bottom with the two long strips
Smooth the tape flat, making sure that there is good contact with the leads

Step 9: The Power Supply

If you are using an AC adapter remove the end of the cable. If using a battery holder the leads should already be accessible
Strip off the plastic at the ends so that the wires are exposed
Fold over the flap of copper tape from the front, trim it so that there is only a small piece about 1cm wide and 1.5 cm long, and tape it to the back canvas with the positive lead from the power supply underneath
With the left over copper tape, cut a piece roughly the same size and tape it to the back canvas connecting the negative lead of the power supply to the end column of copper tape strips on the back.
Tape the cable to the back of the canvas with regular tape, to secure it.
If you want to hide the mess at the back just glue some paper or cardboard to the back to cover it up.

Step 10: Trying It Out

Now it is time to try it out and have some fun. A paint brush is one way to interact with the canvas, try a spray bottle (see first video) or your finger (second video).

Why not try a little science experiment comparing how well filtered water works (or doesn't work) vs tap water, how about rain water, why not add a little bit of salt (be careful, not too much) -what happens?

It is a good idea to wipe off excess water between use, the copper will eventually corrode. I already notice the tip of my paint brush turning blue.