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Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
I have wondered if anyone has tried using aluminum colored paint in bottles instead of salt water. My understanding is that metallic paint is conducive, and imagine that it is possibly better than salt water. Any thoughts?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Metallic paint generally has a high resistance.
When I make saltwater caps I use thick, seven stranded wire, and open it out and twist it so that I get a total of several feet of wire in the bottles (I usually use 2 litre cola bottles). This reduces the resistance considerably, as the most the charge has to travel through the brine is generally around half an inch.
There is as much variation between homebrew saltwater caps as between the manufacturer's capacitors. A good, low resistance electrode is essential for HF stuff.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I imagine silver plating could work quite well, but you still need to be able to get a good connection between the plate and terminal.
You can plate onto conductive paint, but, again, you still need good connections with minimum resistance.
While I've had a lot of success with 'hand rolled' capacitors, etc. over the years, I've not subjected many to the power levels experienced in large Tesla coils. The main factor with any HF application is ESR. There aren't many commercially available capacitors that can withstand the abuse associated with most TC's on the forum, which emphasises how important consideration of ESR in 'home brewed' caps is.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The plating has to be thick because of the heavy currents that will flow. It is easier to just use a bottle with a wide enough mouth and fix thick aluminum foil in side, connected to the central terminal through a springy wire coiled inside for good contact.
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
Why not use an aluminum beer bottle and something like "dip it" to insulate where needed! In my opinion, its easier to use a conductive bottle and insulate than use an insulating bottle and add conductive material. You can also use rubber stoppers to hold your electrode, any science store or home brew store should have both the bottles and stoppers ;)
Registered Member #55389
Joined: Mon Jul 06 2015, 12:38AM
Location: Grand Terrace, CA
Posts: 29
I just had another idea. Use glass beer bottles, place a piece of aluminum foil in the opening, and use glue on the outside of the foil and inflate a balloon in the center forcing the foil to stick to the inside of the bottle.
Registered Member #79
Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673
If you're going to go to all that trouble, you'll probably get more performance out of something like this. I've used these to 45kV but they're reliable to 30kV. They will hold to about 50kV if you put them under oil, and vacuum pump out the air.
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Metallic Paint in Beer Bottles for Caps?
