We used a proxy weight (jug full of water) when filling the balloon to tell us when there was enough helium.  The weight of this jug had to be set to be equal to the weight of the entire payload (parachute and rope included) minus the weight of the filling adapter (the assembly the balloon mouth fits over during inflation).  During inflation, we would stop adding helium to the balloon exactly when it first lifts the proxy weight off the ground.

Remember that the balloon will stretch considerably before it bursts (ours was designed to stretch to 28 feet in diameter).  It stands to reason that a carefully-handled balloon is likely to be able to stretch further than one that is not so carefully handled, allowing the balloon to ascend to a higher altitude.  For this reason, we were very careful to require anyone that handled the balloon to wear soft cotton gloves.

At the same time, the amateur radio equipment at mission control was being set up.

By 10:45am all of the chase teams were on the road and headed for the Prescott and Cornwall border crossings.  It didn’t take long to realise that, with its incredible 200km/h speed and slight northward direction, the balloon would likely cross into the Eastern Townships of Quebec.  We headed instead towards Montreal.