Dry Leyden Jar

20151107_221309

20151107_211634 The Leyden jar starts out with a standard jam jar.
20151107_212115 Pieces of adhesive aluminium foil are glued to the inside of the jar first. This way its easier to see which bits you have missed the strips should not come more than 3/4 of the way up the jar for the highest voltage capacity
20151107_212124 If you can’t get you hand in to the jar to stick the pieces down use the handle of a screwdriver  to smooth out the pieces. The foil does not need to be absolutely smooth, but there must be no gaps. Corona will form on any edge and eat away at the foil.
20151107_212616 Go right around the jam jar until the whole of the inside is covered. to the 3/4 height. Strips of 20-25mm work best. Larger strips become difficult to handle.
20151107_212902  For the bottom of the jar use 25mm square pieces. Stick them on to the end of your screwdriver to position them.
20151107_212835 You may need to use more than one screwdriver to get them to stick where you want.
20151107_211553 Cut a circle of Acrylic bigger then the lid of the jam jar, and cut a circle of copper or brass to fortify the bottom.
20151107_214425 As we are not using water to contact to the inside we need something to stop the foil wearing away a copper of brass circle will spread out the current.
20151107_210851 Stick this down with the foil. You may need to bevel the copper plate slightly as some jam jars have a domed bottom.
20151107_210845 Taking a single sheet of foil slightly longer than the height of the inside foil and wrap it around the jam jar. leaving some spare at the bottom.
20151107_213857 Smooth down the extra over the bottom.
20151107_214121 and add a patch to the bottom and smooth it down.
20151107_214233  Use your finder mail to burnish the outside foil of the jam jar.
20151107_215853 For the inside conductor I used a piece of 5mm copper brake pipe to make securing this easier to the top I used a piece of 2mm copper wire that I attached a ring tag.
20151107_220120 Using another piece of the 2mm copper wire I formed a crude spring around a 10mm drill bit.
20151107_220541 The finished inner contact.
20151107_220740 I glued a 25mm long x 50mm diameter piece of water pipe to the centre of the top circle of acrylic. This fits the inside of my jam jar snugly.
20151107_211431 The top and inner conductor are put into the jar, so that the spring contacts the bottom of the jar. The inner ring is glued into the inside mouth of the jar to stop the spring from pushing the top out.
20151107_214749 A small brass ball was tapped and attached to the bolt from the centre contact.
20151107_211619 The finished jar.
Discharge tool Using a spare piece of the 5mm copper brake tube and  a couple of spare brass balls I made a discharge tool. The handle is made from a piece of nylon bar. Although these jars will not store enough charge to kill, they can pack nasty punch. Better to discharge the jar with an insulated tool.

 

 

 

 

 

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2 Responses to Dry Leyden Jar

  1. Avatar jr maxwell
    jr maxwell says:

    i WONDER IF COPPER FOIL MIGHT BE A BETTER CHOICE., THE BOTTOM COULD BE SOLDERED TO THE SIDES, AND USE A STRAIGHT SIDED JAR..
    i MADE ONE IN THE PAST FROM ALUMINUM, THE FIRST TIME I CHARGED IT THE FOIL BURNT UP, WELL AND ARC AND MELTED A LARGE PORTION OF FOIL. I TRIED TO USE AN OLD AUTO IGNITION COIL TO CHARGE IT.. OUTPUT ONLY ABOUT 4000 VOLTS MAX.
    COULD BE THAT I WAS JUST STUPID TOO. A GOOD CHANCE.

    • I agree, Probably Thicker and able to sustain more current. These jars work well although I have a band of brass on the outside to spread the current.
      I’m only using these on a wimshurst, so they are used as pulse caps not continuous.