This always reminds me of the time they showed it on QI and Stephen Fry said 'are you ready for me to pump my custard?'Custard power (or flour or icing sugar) in a tin - tin with hole in side tube glued in connect to bicycle pump and blow powder over lit candle inside tin - blows lid off - great to demo energy in food
If you haven't a Hydrogen cylinder you can fill balloons using this method after filling a pop bottle by downward displacementHow do you keep hydrogen in a bag? We do balloons of it and ours all have sticker animals on them
If you have a one way valve (where my hand is) and allow some to escape (to vent any air) then connect - no O2 then only H2Zn granules and H2SO4 in a conical flask. Stretch balloon over neck and allow to expand. Only use Peters method if I want to make a mix of H2/O2.
The bottle can be partially filled with one gas, sealed and then the other introduced. Really straight forward. Then using water pressure the gasses are forced into the balloon.If you have a one way valve (where my hand is) and allow some to escape (to vent any air) then connect - no O2 then only H2