At 74 years old I thought I had lots of common sense. I do not! Working on my generator, I needed some insulating varnish. Took a 20 year can from the shelf and tried it. Plugged nozzle so I figured I will punch a little hole in the top of the can and let the air out. Figured it had a pickup tube and just air would escape but put a rag on it just in case. Wrong!! when I removed the punch it instantly soaked the rag with varnish. Then with pressure escaped I thought I could pour varnish into a container and use a paint brush. Wrong again ! it squirted out like it wad still under pressure, and splattered all over my bench. After all this I was able to brush varnish on the wires. You might ask why not buy a new can? None available within 50 miles. Green varnish does not come off your hands easily.
Well at least you tried!
At least you did not heat it! :-)
Jim, My son, about half your age, was cleaning out his shop about a year ago and decided to burn some old aerosol paint cans along with the scraps he was sweeping up. Sure enough, he decided to look into the burn barrel at just the right (or wrong in this case) time when one of the cans exploded. It immediately painted his face and arms with burning paint. I hauled him to the local hospital and they transported him to a Pittsburgh hospital burn unit. By the grace of God he has no scars but probably learned his lesson, at least I hope so!
Jim, that old bench needed a coat of varnish anyway. Green is a nice color. At least you got the wires coated!
Things can develop a bad attitude after 20 years on the shelf.
Aerosol cans can be dangerous. The pressurizing gas (varies with when manufactured and product) mixes with the product much like carbon dioxide in a soda. When the can is punctured, the gas comes rushing out of the product (in this case paint/varnish) carrying some of the product with it. That is both why it will spray clear to the top of the can, and why residual product will spurt when the can is turned over to poor some out as turning the can stirs more of the gas loose.
I am much too cheap to not use old paint cans, and have used them for many protective uses for many years.
First, without shaking the can much, use a small nail, and punch a very small hole near the top of the can. The hole should be so small that the pressure escapes very slowly, a few seconds of hissing for a can that still has its pressure. Then wait several seconds, after which the hole can be enlarged with a bigger nail or punch. A second hole on the opposite side of the can near the top can allow venting of gasses when you attempt to pour a small amount of the product to use (reducing, but not totally preventing the stuff from trying to spray out). If only a small amount is needed, leaving the hole (holes?) small enough to plug with a nail can help preserve additional product for awhile longer and other uses.
I always consider safety, for myself and others. Nearly all empty aerosol cans at my home or shop get punctured and cut open so that they cannot explode with future handling. Paint cans, I cut a hole large enough to keep the marble from inside. I have a few small jars full of paint can marbles. Having seen a few paint cans thrown into fires, I just don't like the idea of leaving them as time-bombs.
If you are going to "do this at home"? It is best to find the safest way to be done.
Oh, and always protect your face and hands. Goggles are good. Keeping your hands and face out of the "blast path" is also important. It only takes a moment to make a mistake you would regret for the rest of your life!
On top of that Almost all cans are pressurized with Propane!
There was a major fire in a metal warehouse equipped with sprinklers that warehoused aerosol paint cans. A fire started in the building I think it started as a forklift fire with a pallot load of paint cans. The building was about 200 feet long separated with two large fire doors that were designed to actuate and close using a fuseable link. The paint cans in the first compartment started to explode like popcorn and traveled into the next compartment igniting the stored paint cans in that compartment before the fire door was able to close. This repeated it self until the entire building was consumed and collapsed flat on the ground. The fire grew so rapidly that the sprinklers were not effective. The sprinkler system was an engineered design as well as the building and the fire doors and still all three systems failed. Nothing is for sure.