after my microwave capacitor died iv'e been looking for a good replacement, id heard of the overhead slide and tin foil ones but i figured i may as well laminate tin foil if i'm going to make that, after messing around a bit with different dielectrics, i made one that worked so well, i decided to make my own instructable on it.
this works great for Tesla coils, Marx generators (if you have the patience to make enough of them), and other high voltage aplications

Step 1: Stuff

items consumed:
1/2" PVC (and a little 4" but that's optional)
about 10" of wire
aluminum foil
black plastic
duct tape (unless you say its a tool) <ans store:A>

tools:
<insert "duct tape", if A=1>
scissors
tape measure

work space: id recommend sweeping first, you will get better results.

<don't freak out if you don't know any programming languages, its just a joke.>

Step 2: Lets Get Started!

this is the second one i have built and yes it is quite a bit larger, the first pictures are the original and the last one is the first step in the construction process
lay out the plastic and put the tin foil on it

Step 3: "its Got a Light Side and a Dark Side and It Holds the Universe Together"

no you will not be taping the whole tin foil surface, only the ends on this one, i made an improvement, anyway tape the ends MAKE SURE ITS FLAT
measure out twice the with of the tinfoil + 2" overhang and cut off the rest of the plastic then fold it in half

Step 4: Wire It!

you can duct tape them, or use foil tape like i did
then tape the ends of the plastic and fold it in half the other way

Step 5: Roll It Up

get some 1/2" PVC and roll it as tight as possible then you can string it shut, stick it in a tube (that's where the 4" PVC came from) or whatever, but make sure it can be re-opened

Step 6: "hey I Thought You Said This Was Adjustable!"

it is, remember i wanted you to make it so it could still be opened? well just stuff some more black plastic (or newspaper, plastic, fiberglass, flux, etc) in there and you can adjust to the desired voltage capabilities/ capacitance.