In this Instructable, you will learn how to build your own vacuum chamber using common tools, a vacuum pump, and a few inexpensive or easy-to-locate materials. I suggest reading the entire Instructable before beginning this project, simply so that you will have a better idea of what the finished product should look like. I have written instructions to guide you around making significant mistakes, all of which I learned the hard way. :) Hopefully, this will make building your vacuum much simpler and stress-free.
The items you will need are as follows:
-- a silicone baking mat
-- silicone caulk (and caulk gun)
-- power drill
-- a 1 in thick board of HDPE (high density polyethylene) plastic. This can be ordered for less than $30 bucks.
-- a glass bell jar
-- a vacuum pump (more details later)
-- if needed: detergent-free motor oil
-- 4 plastic soda bottles
-- vinyl tubing, preferably very thin and strong
-- vacuum pressure gauge. A cheap one may be $5-$8
-- vacuum grease
Now... what is a vacuum chamber? What are they useful for? If you are well aware of how vacuum chambers work, and their uses, then by all means skip to the first step.
A vacuum chamber is an area from which the air has been evacuated. The pressure inside the chamber is actually a negative value (i.e. -8.3mmHg, -1Bar, etc.) because the outside atmospheric pressure (about 101,325 pascals or 14.6959 psi) is pushing in on the chamber. In other words, the pressure inside the chamber is far, far less than that outside the chamber. Why is this useful? Well, if all the air is gone then there is no "atmosphere" to interact with whatever you place inside the chamber. Vacuum chambers are used in life sciences to preserve specimens, such as bacteria cultures, in order to store them and keep them from decaying. In physical sciences, the vacuum chamber is incredibly useful in projects involving electricity or optics because the lack of air reduces resistance and interference from gas particles. This helps induce arcing, like what you see on a tesla coil.
Did you know?
The vacuum tube (a small, glass-covered vacuum chamber), was used by Thomas Edison in his invention of the light bulb in 1883 and by Sir John Ambrose Flemming in his invention of the diode in 1904.
Step 1: Create a Seal
In this step, you will need the silicone baking mat, a pen or sharpie, silicone caulk, and the bell jar. You may also want to grab some wax paper or foil and a big, heavy book.
The baking mat you can buy at Hobby Lobby or a home/kitchen goods store. It will be used to make the seal. For the silicone caulk, be sure it is actual silicone.
A few notes on the bell jar... make sure that it is actually a bell jar, as in a glass jar with a rounded dome on top. A cake dome would also work. It is important that the top of the jar be convex because this structure is stronger and will withstand the pressure pressing inwards better. If you use a regular canning jar, for instance, the bottom may curve inwards. This concave structure runs the risk of breaking under pressure and collapsing on itself.
Now, to begin the seal. Trace the rim of the jar onto the baking mat twice, spaced apart, on the right and left sides. Draw an inner circumference and an outer circumference for both circles, about half an inch away from the original circles. Now, cut out both circles along the inner and outer circumferences so that you have two baking sheet rings.
Apply a generous ring of caulk around the top of one of the baking mat rings and place the other baking mat ring on top. You want to apply pressure to adhere the rings together as evenly as possible. A good way to do this is to place a sheet of aluminum foil/wax paper on a table, put the silicone rings on top of that, then another sheet of foil/wax paper, and finally, on top a nice big, heavy book. Do not try to flatten the rings together manually, or you will end up with a bumpy seal that destroys your vacuum.
Let the silicone caulk dry, and then you can trim off any excess with scissors. Consider yourself warned, the silicone caulk is smelly.
This double-thick silicone baking mat ring will be the seal for your chamber.
Step 2: Attach Seal to Plastic Base
In this step, you will need your seal, the 1" thick board of HDPE (high density polyethylene) plastic, a sharpie, and the silicone caulk.
Place your seal on top of the HDPE. Position it so that it is in one corner on the top of the board, so that two of the sides of the board are tangent with the outside edge of the seal. Trace the seal with a sharpie.
After removing the seal, Apply a generous ring of caulk to the board between the sharpie lines. Place the seal back on top. Like you did before, put a piece of aluminum foil on top and a big heavy book on top of that. Let dry.
If you want you can use your finger to smooth out the excess caulk along the edge of the seal. Your seal should be as flat and smooth as possible, and be sealed to the board on all sides.
Step 3: Drill Tunnels in Base & Insert Tubing
In this step you will need a power drill, vinyl tubing, and silicone caulk. The vinyl tubing should be pretty small and strong. I used the vinyl tubing that goes with a nebulizer, because I had extra.
Get out your power drill and drill bits.The drill bit you should use should be roughly the size of the vinyl tubing.
Mark a point inside the seal on the top of the board. From the 1" thick side of the board, drill through the plastic until the tip of the drill is underneath the point on the top. It is a good idea to measure the drill bit and the distance to the point from the side of the board, so that you have a good idea of how far in you need to drill.
Drill from the top point down into the tunnel from the side. The two tunnels should open into each other. It is very, very important not to drill all the way through the plastic while drilling downwards.
On the 1" thick side of the board where you drilled in through the side, drill two more holes on either side. For these holes, drill diagonally into the center hole. These tunnels should open cleanly into each other.
Cut three lengthy pieces of the vinyl tubing. Insert one end of each into the 1" thick side of the board.
Step 4: Create Pressure Release Valves
For this step, you will need 4 plastic soda bottles, scissors, silicone caulk, and the drill. Electrical tape may come in handy.
Using scissors, cut the tops off of 4 plastic soda bottles, just underneath the lip. Make the cut surfaces as smooth as you can.
Use silicone caulk to seal the cut sides of two of the bottle tops together. If you want, wrap electrical tape tightly around the outside to hold them in place and let the silicone dry completely. Be sure that the silicone does not seal up the inside of the bottle tops completely, and that at least one of the screw-on lids is still removable.
Do the same for the other two bottle tops. These attached bottle tops are going to be your pressure valves.
In the cap on one side of each valve, drill a hole through the cap. This is so you can insert the vinyl tubing.
Step 5: Attach Pressure Gauge and Valves
This step will require the vacuum pressure gauge, both pressure valves, and silicone caulk. Electrical tape may prove useful again.
On the ends of each of the three pieces of vinyl tubing, attach the pressure gauge to one, and pressure valves two the other two. Seal the pressure valves to the tubing with silicone.
Attaching the gauge may be a trick because the gauge is probably much wider than the tubing. Just use whatever works that is airtight and can connect the two together. (I used a plastic part that the mask screws onto on the nebulizer tubing.) Electrical tape may come in handy again along with silicone to accomplish this.
Step 6: Attach to Pump and Seal With Caulk
This step will require the vacuum pump, rubbing alcohol, vacuum grease and silicone caulk.
If you do not want to buy vacuum grease, ask around and see if anyone has some you can borrow. You won't need much.
There are three ways to get a vacuum pump if you do not already have one. You could buy one, borrow one, or make one. There are ways of making a vacuum pump out of an old refrigeration compressor or by converting a pancake compressor, but I would recommend researching that elsewhere.
How to attach the vacuum pump may depend upon what your pump is like. Use one of the pressure valves to attach the pump. If the tubing could attach directly, you could cut the pressure valve off entirely. Do whatever is necessary to create an airtight seal between the pump and the tubing.
In order to prepare the chamber to be turned on, clean of the seal on the board with isopropyl alcohol (rubbing alcohol), apply a thin layer of vacuum grease to the bottom of the bell jar, and place the bell jar on the seal. Press down on the bell jar as you turn on the pump.
Air will leak through the space between the tubing and the plastic base. Apply caulk around the tubing on the edge of the board. It is good to do this while the pump is on, because it will slurp the silicone into the small space between the tubing and the plastic. Turn off the pump and let the caulk dry.
Step 7: Checking for Leaks
After the silicone is dry, press down on the bell jar and turn on the pump again. You will now proceed to look for vacuum leaks. This step is critical in getting your vacuum chamber to work!
Observe the reading on the vacuum pressure gauge to see if you are pulling a good vacuum. Check thoroughly for leaks by listening for hissing air and looking for holes. Seal any leaks you find with silicone.
A good way of checking for leaks near or on the tubing is to pinch off areas of the tubing or blocking the hole into the chamber and observing what that does to the pressure shown on the gauge.
Researchers, scientists, and engineers are always battling vacuum leaks. Blocking them is important because even a small vacuum leak can destroy your vacuum.
Step 8: Testing and Applications
Now that your vacuum is all sealed up, turn it on and see how low the pressure will drop on the gauge.
One thing you can do to test your vacuum is place a crushed plastic soda bottle with an airtight lid inside the chamber. As the vacuum is pulled, the bottle should inflate to its original state. Once the vacuum is released, the bottle will crumble again.
A vacuum chamber can be used in loads of awesome science projects and many other things. For example, you could run wires through the base to preform electrical experiments in a vacuum. It certainly helped me!