Capacitors can pump charge into each other with the help of rectifier diodes and a changing voltage. This won’t actually double the voltage, due to the voltage drop of the diodes, but it will be close to double if the starting voltage is a bit high to begin with.
Nice looking larger value capacitor kit.
Improved circuit schematic diagram
When the switch is connected to ground, it charges the first capacitor.
When the switch connects to Vcc, it puts the charged capacitor in series with vcc so that their voltages add up while charging the second capacitor.
Must keep repeating fast enough that any load at Vout doesn’t discharge the second capacitor.
Remember that the diodes drop 0.7 every time current goes through them.
White version of the oscilloscope that I use in many of my recent videos.