Wanting to do some experimenting in a vacuum, I sought out a low-cost vacuum pump. I found all kinds, but by far the least expensive, and best-bang-for-the-buck, was an aspirator pump. These can be run on either air or water. The one I chose will use water. I got a Thermo Scientific Nalgene water aspirator pump. It is suppose to be good for a max vacuum of 28.5″Hg.
I found mine on eBay for the lowest price I could find anywhere (around $16). Here are some pics showing the unassembled pieces as they were packaged:
The threads on the aspirator are 3/8″ NPT. I needed to adapt this to my faucet, which has standard faucet threads. After a quick trip to Lowe’s you can see what I can up with:
The finished product:
Testing
Right away I ran into a problem. As I was trying to hook this up to my kitchen faucet, I discovered the faucet adapter was just too short. Fortunately, I had a longer one laying around that I use for the water vacuum for my aquarium, called a ‘Python brass adapter’, like this one:
Upon first testing, I must say, I was impressed by how much this thing sucks! That is, the vacuum it creates is impressive. Without a proper vacuum chamber yet, I was left to my creativity… so, I stuck the hose in a nearby empty plastic water bottle, used some plastic wrap for a make-shift seal, and had at it. In no time, the bottle was nearly completely flat. A second test, this time making use of a baby medicine syringe, I filled it partially with water, plugging one end with a rubber sheet, the other I attached my vacuum hose. Right way it began to bubble, or boil, vigorously. Awesome! There was also a noticeable temperature change, as I began with ~100F+ degree water, ending 30F or 40F degrees colder.
Here’s a short video demonstrating what happens to a marshmallow in a vacuum:
Here’s what’s happening:
- As the pressure drops, the small air pockets trapped within the marshmallow expand, causing the marshmallow to expand.
- As the air escapes the marshmallow, it slowly returns to its “original” size.
- Once I abruptly disconnect the vacuum hose, the pressure inside the jar increases rapidly, essentially “crushing” the now “hollow” marshmallow.