Hysol 1C "I don't get no respect"
Posted: Sun Mar 18, 2007 7:38 pm
There seem to be some rumors that Hysol 1C is over rated and maybe should even be shunned for use in high vacuum work. This reputation is really undeserved and most probably the result of the products misapplication. If your system leaks, find and remove the source of the leak. Using any sort of patching material as a sealer is far removed from any good vacuum practice.
If, on the other hand, you want to join two parts together to form a reliable and tight seal that has to work in a high vacuum environment, this epoxy is hard to beat. Of course there's always welding or brazing, but if you're trying to join dissimilar materials your going to run into problems with these methods. 1C to the rescue! When properly mixed and applied, (to an absolutely clean surface) it will withstand a 150 deg.C bake for hours. (maybe indefinitely, but my own tests can confirm the several hours claim.)
Now, some might say "yeah, if your pump is big enough you can make a booger look like a good high vacuum material!" Well, maybe, but the acid test is to have a significant amount of 1C exposed to the inside of a high vacuum experiment and then hard seal the experiment. How long can a useful vacuum be maintained under those conditions, especially if some of the sealed-in parts are elevated to incandescent temperatures? Few folks have actually done the test.
There are tables and graphs and manufacturers claims that can be referred to. All well and good. I sometimes fall prey to them myself. But, at the end of the day, I'm still a pudding taster.
The posted photos show some of the results of using 1C to seal homemade vacuum triodes. I built these back in 1994 (Steve H. can probably verify the era of that lunacy). Anyhow, they've been sitting on a shelf quietly composting for 13 years now. I decided to test there serviceability today and fired several of them up. They still work!
As can be seen along the base seal, I was most generous with the 1C on both sides of the joint. The test today was to run the filaments for 15 minutes each and check for any sign of resistance change in the heater. If there is any loss of filament material due to air or contamination, this very small diameter tungsten does a self-destruct and turns into a cloud of white powder in a couple of seconds.
The power input didn't budge.
If, on the other hand, you want to join two parts together to form a reliable and tight seal that has to work in a high vacuum environment, this epoxy is hard to beat. Of course there's always welding or brazing, but if you're trying to join dissimilar materials your going to run into problems with these methods. 1C to the rescue! When properly mixed and applied, (to an absolutely clean surface) it will withstand a 150 deg.C bake for hours. (maybe indefinitely, but my own tests can confirm the several hours claim.)
Now, some might say "yeah, if your pump is big enough you can make a booger look like a good high vacuum material!" Well, maybe, but the acid test is to have a significant amount of 1C exposed to the inside of a high vacuum experiment and then hard seal the experiment. How long can a useful vacuum be maintained under those conditions, especially if some of the sealed-in parts are elevated to incandescent temperatures? Few folks have actually done the test.
There are tables and graphs and manufacturers claims that can be referred to. All well and good. I sometimes fall prey to them myself. But, at the end of the day, I'm still a pudding taster.
The posted photos show some of the results of using 1C to seal homemade vacuum triodes. I built these back in 1994 (Steve H. can probably verify the era of that lunacy). Anyhow, they've been sitting on a shelf quietly composting for 13 years now. I decided to test there serviceability today and fired several of them up. They still work!
As can be seen along the base seal, I was most generous with the 1C on both sides of the joint. The test today was to run the filaments for 15 minutes each and check for any sign of resistance change in the heater. If there is any loss of filament material due to air or contamination, this very small diameter tungsten does a self-destruct and turns into a cloud of white powder in a couple of seconds.
The power input didn't budge.