This pressure chamber is great for several educational experiments. However there is a certain level of danger involved.
NOT ALL SODA BOTTLES ARE CREATED EQUAL AND A SAFE PRESSURE FOR ONE BOTTLE MAY BE THE RUPTURING PRESSURE FOR ANOTHER. EXERCISE CAUTION AND WEAR EYE PROTECTION WHILE FILLING THE BOTTLES. DO YOUR OWN RESEARCH FOR SAFE BOTTLE PRESSURES.
You will need a soda bottle, a bike pump, the stem from a bike inner tube, scissors, drill bits, a drill, and blue RTV silicone.
Step 1: Cut the Stem.
Cut the Stem off of your bike tube near the base. Leaving a dime sized piece of rubber at the base.
Step 2: Drill the Stem Hole
This is pretty self explanatory. For my stem I used a 1/4"drill bit. Make sure it is a snug fit.
Step 3: Roughing It Up.
The silicone will make a better deal if it has a coarse surface to grab onto. Take a knife or razor and put some scratches on the top of the lid and on the base of the stem.
Step 4: Make the Fit
Unscrew your stem cap and push the stem through the bottle cap.
Leaving a little space at the base of the stem for silicone application.
Step 5: Seal It Up
With your stem now in the bottle cap apply silicone at the base as shown. Be sure to use a small bead of silicone and don't allow any to get on the threads of the cap.
Once applied pull the stem and twist it to evenly distribute the silicone and make it snug.
Now apply a liberal amount of silicone to the top of the cap and work it into the hole with your finger while simultaneously smoothing its surface.
Step 6: Let It Cure
A simple but important step. Let your silicone cure a full 24 hrs before using your pressure chamber. Failure to do so will result in a leaky seal and will require redoing. Patience is key.
Step 7: Finshed
With the silicone cured you are ready to go. Attach the bike pump to your pressure chamber and pump up the pressure to an amount you have determined safe.
Once again there is a certain level of danger in this project. Especially to the eyes. Please wear eye protection at all times and most of the danger is gone.
Some of my favorite activities for this pressure chamber are releasing the pressure all at once by unscrewing the cap. The confined air rushes out and produces a chilling effect to the hand.
If you place marshmallows inside and bring the pressure up the will shrink slightly. If you allow the marshmallows to return to their normal form and then release all the pressure at once they will expand greatly and have a fluffier texture compared to the normal marshmallows.