Super Simple Vactrol Construction

I start with a tiny light dependent resistor and an amber 3mm LED (use a yellow LED if possible). These two are going to be good friends.

I pushed the LED and photoresistor flush together, then place the kissing components down on a bit of electrical tape.
Thus begins a very long staring contest.

Now roll the tape around a couple of times. Bend the component leads apart and press the tape together in between in order to keep light out.

I then take a thin strip of black tape and wrap it between the leads horizontally.

Squeeze around on the tape a bit in order to seal any openings. (Remember the round leads go to the resistor, the square-ish ones to the LED) You can check to see if there are leaks by hooking the resistor leads to a multimeter - in a dark room shine a flashlight on both ends of your new vactrol. If the flashlight changes the resistance reading on your meter then you have a leak and need to seal the package a bit more.

This is definitely a quick fix, (a sturdier vactrol should be constructed using epoxy or perhaps silicone adhesive) but I've found these to be a great way to control resistance. Just add a little LED flasher circuit and you're good to go for all sorts of effect pedal, synth, and general electronics mods and designs.

PS - Here's an LED flasher circuit:
blog.makezine.com/archive/2006/10/blinking_eyes_c.html