Very good Stevie, I'm glad you tested this.
You probably know this already but since you haven't experimented with chemicals before, here are some tips I have learned.
For best efficiency using chemicals we need the following:
Keep voltages between electrodes under 2.6 volts. yes more voltage does make more gas, but efficiency drops.
now for the GAP: It needs to be a compromize, smaller is better, but needs to be big enouph for the gas to escape and water take its place.