Hi Ron,
Here is an excerpt from the Nafex board on using Parafilm -
Ji Gina, etl,
Absolutely use a grafting rubber then cover. Even with whip & tongue it can be difficult to keep the scion lined up perfectly with the understock. Lock first the band on the understock then wrap upwards catching the very bottom of the scion on the second wrap thus holding it in alignment. Don't be afraid of pulling the rubber too tight. But be prepared to cut the band after it takes to prevent girdling.
Had someone call me the other day asking why his success rate was very low. He was using masking tape only then covering with a plastic bag to hold in moisture. It is very difficult to maintain alignment w/o the rubber. Even a plain old rubber band works, but must be cut later as they normally don't deteriorate as fast. Proper alignment is vital, close only counts in horseshoes and hand grenades. There are always exceptions and one is apple. There alignment isn't nearly as important as walnut & pecan.
As for storing the Parafilm in the frig, a 250 foot roll can last for years. Over a long period of time, say two years, it can dry out along the edges loosing it's elasticity. You are right, in the lab where a roll us used up more quickly refrigeration isn't necessary.
Sherwin