Step 2: Hollow out the light bulb
A lot of the time you are poking around inside the lightbulb trying to break off the internal glass bits. Do this over a trashcan and often shake the lightbulb out over the trashcan to get rid of the glass shards. Wear safety glasses at all times. More than once some glass flew up towards my face when I was doing this.
First, grip the metal circle with a blob of solder in the middle at the bottom of the lightbulb with your pliers and gently pry it up from the dark purple glass insulator. This is pulling a wire in the middle that you want to break, so just pull it off.
Once that is done, take your carbide scribe and over a trash can, pry into the hole you just made in the purple glass insulator and break up that purple glass. You want to remove all the purple glass insulator from the lightbulb body. I use the scribe to start some cracks and lift off a section of it, then I follow up with the screwdriver to get the rest. Turn the lightbulb upside down and shake out all the glass bits that have fallen inside.
Inside there is a small glass tube that pokes up into the glass insulator. You might or might not have already broken that off by now. If not, just lever the screwdriver against it until it snaps loose. Empty into the trashcan.
Now you have a hole in the bottom of the lightbulb. At this point I take my pliers and gently bend over the metal tabs on the inside of the hole so there is no "lip" on the inside. Later when you have broken up the rest of the inside pieces, there isn't anywhere for the bits to catch and stay in the lightbulb when you shake it out.
There should be a wire visible inside that's soldered to the side of the metal screw piece. Take your wire cutters and cut the wire as close to the side of the bulb as possible.
Now, the inside has a glass cylinder you need to break off and clean up the edges to finish the job. Take your scribe or screwdriver and put it down into the lightbulb until it meets resistance. Tap it gently until something breaks. Then using the screwdriver, lever against the side of the lightbulb to clean out whatever remaining glass bits are left. You want the neck of the lightbulb to be clear from the hole all the way down the body. Turn the bulb over and shake it out one more time to get rid of the last of the internal glass pieces floating loose.
Take a toothbrush and while dry, push it into the lightbulb and start loosening up the dry white powder. Especially in the neck of the bulb. Don't worry if you can't get the stuff the toothbrush can't reach at this point. I found the bulb cleans out easier if you do loosen up the white powder in the neck before it gets wet.
Now take it over to the sink and add a little soap and water. Scrub around with the toothbrush and shake the bulb to get the water everywhere. Pull out the toothbrush and then wash out the soapy water from the bulb. At this point it's all nice and clean inside without any soapy residue. Set it aside to dry out. Now it's time to mix up the concrete.