This is a jar made from a film canister. The original picture and how to build it are on Lenny R's web page. There's also a quick and dirty (but very effective) static generator there.

This is one of my jars. It's made from a polyethylene food container. The ball on top has a coating (graphite) that allows a spark to travel along its surface (as well as jumping the gap).

Here's a fine jar made by PV Scientific Instrument company. They make   reproductions of many classical laboratory instruments.

A Leyden jar is a device that early experimenters used to help build and store electric energy.  It was also referred to as a "condenser" because many people thought of electricity as fluid or matter that could be condensed.  Nowadays someone familiar with electrical terminology would call it a capacitor.

Basically, the Leyden jar is a cylindrical container made of a dielectric (that's an insulator, like plastic or glass) with a layer of metal foil on the inside and on the outside. With the outside surface grounded, a charge is given to the inside surface. This gives the outside an equal but opposite charge. When the outside and inside surfaces are connected by a conductor...SNAP! You get a spark and everything returns to normal.

The amount of charge one of these devices can store is related to the voltage applied to it times its capacitance. In simple terms, capacitance depends on the AREA of the foil or metal, the TYPE OF MATERIAL between the two layers of foil, and the THICKNESS (generally the thinner the better) of that material.

Check out  static tube  for a simple way to charge a Leyden jar. Another way to charge a Leyden jar, If you haven't got a high voltage generator, is to use an electrophorus.

A few pointers for constructing Leyden jars:

• Avoid making sharp points or edges anywhere on (the metal parts of) your jar because they will leak charge. For example, a cap nut screwed on to a screw is better than a bare screw, but a ball attached to a smooth metal rod is better than either. Creases and wrinkles in the foil, and poorly cut edges on the foil can be a major leakage source. I would also suggest not attaching any fine tipped pickups right to the jar. While they collect charge really well, they also leak it really well. I have had no trouble charging jars without collectors on them, just by rubbing a piece of PVC pipe with rabbit fur along the top ball (it doesn't even have to touch).
• Use a cylindrical container. You'll find that the foil is easier to apply and will have fewer creases.
• The fewer seams in your foil the better.
• Leave plenty of space at the top of the jar without foil (about a third of the total height). If the metal is too close to the top the jar will "spark over," meaning that a spark will jump over the edge of the container before it is fully charged.
• Don't forget that the outside of the container needs to be grounded some how while it is being charged.
• The container must be made of a dielectric. Forget wood, and even most ceramics. Anything that can absorb moisture is out. Plastic is so easy to come by I almost didn't mention this one. You should also know that some plastics will work better than others.
• Try to use a container that is free of blemishes, scratches, or gouges. Even though a thinner container is generally better, a spark can "puncture" the dielectric if it is too thin for the voltage being applied. This will happen at weak spots in the container.
• Tightly glue or attach your foil to the jar's surface. Air gaps between the foil and the container are a problem.
• Don't get hung up on these "tips," they're here as a reference, not as a set of rules. Play around, have fun, observe, and learn. I've made jars that contradict many of the above suggestions and they do interesting and unusual things.
• Don't underestimate the role that humidity plays when generating a frictional charge. In a very humid environment it can seem nearly impossible to get any sparks at all. When things are really dry, however, look out. Having a hair dryer around can help on those muggy days.
• Turn out the lights, let your eyes adjust, then play around some more. You'll see things you never knew existed.

A 1.6 pint container	Frosting can.	This is an electroscope. In the presence of a static charge imbalance the loosely hanging foil leaves repel each other.
Discharge tongs		The electrode and stem from one of my Leyden jars.

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Basic Anatomy

 With some thought and research, excellent Leyden jars can be made using common materials. For those who don't have the time or resources to devote, there are people and companies that sell Leyden jars or other electrostatic related equipment.

Something to keep in mind as you digest all of this is that the length of spark an electrostatic machine can produce is not directly dependent on the capacitance of the Leyden jar connected to it.  The energy in the spark is directly related to capacitance (and voltage). In other words, I'm saying that if you want a longer spark you won't get it by just making a bigger Leyden jar. You'll get a hotter, louder, more visible spark. Learn more about, and improve, the design of your machine.  I'm no genius when it comes to the laws governing electricity, but there's one thing that I am positive about: These things get more dangerous as they get bigger.  Once again, let me say it another way: The pain a fully charged Leyden jar can inflict varies directly with its capacitance. Small ones are almost like toys, larger ones can leave you on your butt wondering what just happened. Don't fool yourself into thinking that a couple of pieces of tin foil can't be dangerous.

Don't just take my word for it, though, see what Benjamin Franklin had to say when he shocked the  #$%^&#!  out of himself.

Other simple capacitors
More info about materials to use for electrostatic experiments.
Back to the Static Generator Page