I've had that problem! Depends on hardeing/curing time. System THree epoxies come in different speeds. That & the room temperature make a difference in whether you'll see a problem. Me personally ... I use small-medium sized clear plastic drinking cups (disposble) that you can get cheap. I usually have more of a problem with my brushes, rollers, & disposable paint trays affecting subsequent batches of epoxy.

: I'm getting to the point where I'll be laying up the fiberglass fairly soon.
: Everything I've seen recommends mixing up only 2 or 3 ounces of epoxy at
: one time.

: When mixing up small batches of expoxy, do you need to go to a clean
: container when mixing a new batch? Does the unhardened epoxy left over
: from the previous mix cause an acceleration of the gelling of the new mix?

: Wade