If you’ve got a shop, you’ve probably got some source of vacuum around, even if it’s only a residential vacuum cleaner for tidying up the floors. And in a pinch, a home or shop vacuum cleaner will do for light duty vacuum applications like running a small vacuum former.
If you’re doing chemistry, however, and may be dealing with organic solvents and their vapors, a vacuum cleaner is not only unsuitable, but unsafe: The plastic parts will degrade in the presence of many organic solvents, and the electrics—which are almost certainly not explosion-proof—may ignite their vapors.
But a proper laboratory vacuum pump is a pricey space hog. Whether you opt for the cleaner, lighter duty diaphragm-type pump or the top-of-the-line heavy duty rotary vane oil pump, you can expect to be out a few hundred dollars, a couple cubic feet of storage space, and several hours a year in maintenance time. If you’re just performing vacuum filtration, stripping solvent, or keeping a dessicator pumped down, it’s not really worth it.
A water aspirator is a common and effective compromise solution. Attached to a faucet, a water aspirator uses the Venturi effect to produce vacuum at the sidearm from the downward flow of water out the bottom. It’s cheap, effective, and reliable, with no moving parts to wear out or maintain. But there are some drawbacks: You need to work near a sink with a faucet and a drain, you have to keep the water running to maintain the vacuum, and all that can make it difficult to maintain dry conditions if your chemistry requires it.
If your shop has an air compressor or other source of compressed gas, however, you can use an air aspirator, also called an “air ejector” and a “Venturi pump,” to create vacuum for light duty lab work. An air aspirator works just like a water aspirator, in principle, but it uses high-pressure air as the working fluid, instead of water. Air aspirators offer all the benefits of water aspirators but with few, if any, of their drawbacks. Analogous devices are used in some vacuum clamps marketed to woodworkers for holding down flat stock during routing or sawing.
I’ve used several of these. The particular model shown here is a Vaccon FastVac VP10-150H that I bought used as part of a mixed lot of ten. Running compressed air from my Makita MAC2400 at 80psi, it works at least as well as any water aspirator I’ve ever used, and better than most. Comparable models are currently selling on eBay for $50-$100, which is only a bit more than a top-of-the-line water aspirator.
If there is a major drawback, it’s that this beastie is loud. Mine came with a detachable silencer, shown removed in the photo above, and it helps quite a bit, reducing the white noise level from “obnoxious” to “bearable.” You’re still not going to be carrying on any intimate conversations with this thing running nearby. The neighbors probably won’t come over to complain, but they probably would if you turned the music up loud enough to enjoy it over the din.