Well, to be honest, I am very disappointed with it. I filled one balloon with hydrogen I obtained from reaction which occurred after mixing some sodium hydroxide dissolved in water with aluminium foil. Little displacement (about 5 grams) is probably caused by impure hydroxide which I used. At this moment buying that ingredient would be more problematic than buying whole bottle of helium so I decided to do it. While I’m waiting for the shipment I decided to do more tests, so tomorrow I’m going to use all supplies I’ve got to fill as many balloons as it will be possible. There is one more issue I need to consider. After buying these small balloons (30cm of width) I found on the Internet place where I can buy one that has 1 meter of diameter. I think of using two of them instead of plenty of these smaller.