High voltage in vacuum

This is my first test with high voltage in a vacuum. The vacuum is 25 " HG. The power source is an old ignition transformer from an oil burner. The voltage should be some where around 10kvac.

I did not take tim to properly anneal the tube while building it. There is a leak somewhere. After testing the tube for about 30 seconds it over heated and developed a large crack near one of the electrodes. The tube has served its purpose as i am still learning to work with glass.

Evacuation of tube with electrodes

The other day i managed to make a T connection between two tubes. I then removed most of the air from the tube(25" Hg vacuum). After i verified that the tube did hold vacuum i put some water in it. I did a test boil while attached to the vacuum to be sure that the boiling water would not overcome the vacuum. While testing the water boiled and as far as i could tell the vacuum did not change. I then sealed off the connection to the vacuum pump and began to heat the sealed tube. 

I began to boil the sealed tube. After about 20 seconds the tube started to make noise and then it changed from transparent to translucent. All of this took place in less than 1/10 of a second, my initial thoughts were that something was going to happen so i started to turn my head and just then the tube exploded.

I realized that the vacuum was lost when i tried to seal the tube from the pump. The tube came to atmospheric pressure and was sealed. This is why the tube exploded when i began to boil the water.

I was holding the tube by the portion that was sealed off from the vacuum pump. When the tube exploded a portion of glass struck my thumb. This cut my thumb very deep, about 3/8 " deep and about 3/8 " wide.  Alot of "meat" was hanging out and my thumb was bleeding rather heavily. I allowed it to bleed for about a minute and then stuffed the meat back into my thumb. Then i pinched my thumb into my middle finger to stop the bleeding. While cleaning up the busted tube i found the peice that had struck my thumb. It was shaped like the cutting edge of a wood chisel.

After a few minutes of pinching my thumb i decided to assess the damage. It looked like it should have atleast 4 stitches. Instead of going to the ER i grabbed some electrical tape.  The next day the thumb was very soar. I couldnt even move it. I took the tape off and put a home made split on and put a new wrap of electrical tape on. The next day i inspected my thumb again and found that it was healing nicely. Once again i put a home made split on and applied a new wrap of electrical tape.  This went on for 3 days and then i allowed my thumb into the air.

My thumb is almost completely healed now (day 5). So i started to make another T tube. This time i added electrodes. Now i had a T tube that holds a vacuum and it has electrodes.

The tube in the picture is my second T tube. I never got a chance to get a picture of the first tube prior to the explosion.

I may attempt to put some CO2 into this tube in order to conduct my first experiment.

Tinkering with soda-lime glass

Apparently soda-lime glass is pretty much chemically inert. It also has different absorption characteristics than regular silaca glass(Sio2). 

Sio2 does not absorb UV light but soda-lime will not allow anything below 400nm to be passed.

Another feature is that soda-lime has a fairly low working temperature when compared to Silica or even boro-silicate.

The picture above shows some of the tubes i created. They all cracked at the metal-glass joint since i did not take time to properly anneal the tube. I found that it is much easier to insert electrodes that have a small bead of glass previously prepared. One the tubing is at working temperature i heat the glass bead near working temperature and insert it into the tube. The two bond almost at an instant.

I still have some things to figure out when working with the electrodes. 

First attempts

These are my first works. The smaller tubes are borosilicate lab tubing and the larger tube is fluorescent light bulb section. My goal is to make custom electron tube experiments.

The afar left tube is sealed. Initially i sealed on end and then annealed the tube. After it cooled it inspected it and supplied a small amount of pressure with a rubber bulb. I then tried to form a bubble using the rubber tube. I found this to be pretty difficult as the bubble would get out of control rather quickly. After working with the tubing i found that expanding air inside the tube had enough force to form a good bubble. This was also a lot easier to control than squeezing the rubber bulb.

After forming a small bubble i added some water. I thought this would be a good way to test myself.
Since most glass work is done using gravity i would be quite a challenge to have water in the bubble.
With the water i could no longer use gravity since the water would rush down into the working glass and likely to crack it.

I was able to seal the end of the tube while the water was in the tube. I then tried to make another bubble but got ahead of myself and almost burst the bubble. It is very difficult to work the bubble being that the glass is stretched very thing. Instead of attempting to repair the bubble(which skilled glass workers can do) I moved closer to the center of the tube to form another bubble.

All in all the first sealed tube turned out quite well as far as i am concerned. 

For my second tube i thought i would again seal the end of a tube and create a bubble in the same end.
The other end of the tube was drawn out so as to create a very small inside diameter. This challenge was two-fold. First to create a small diameter tube and secondly, put a small amount of water inside the tube. This process is very similar the construction of a thermometer. While reading the glass working books i found the method of which they filled the thermometers very notable. To add a liquid to a tube that has similar construction of a thermometer simply place the tube into the liquid and heat the bulb. A portion of the expanding air inside the tube will be forced out of the tube. The tube is then cooled while in the liquid. The cooling process causes the air inside the tube to contract which in turn draws the liquid into the tube.


The last tube in the picture is from the fluorescent light bulb. I broke a few sections while getting a feel for the glass. I have found that it is much easier to work the glass if it is very slowly brought up to working temperature. Pretty much the annealing process in reverse. Then after the tube is upto or near working temperature it is annealed.

Once cooled this glass tube can be brought up to working temperature at a respectful rate. In order to seal the end of the tube i discovered the end of a 12oz soda can to be a very good tool. The concaved structure allows the tube to roll over into a dome which occurs very quickly. Initially i tinkered with gravity to seal the end. This works but seems to take a great deal of time.