[ArtcoInc]

Franklin, correct me if I'm wrong, but you are working just with soft glass, right?

The bigger the marble you wish to make, the larger your torch will need to be. The larger your torch, the more oxygen you will need. So, as I see it, your biggest limitation will be your oxygen supply:

If you use bottled oxygen, the bigger your torch, the faster you go through a bottle.

If you use a concentrator, the size of your concentrator(s) limits the size torch you can run. And yes, you can gang up several concentrators to increase your oxygen supply.

So, if you are on concentrator(s), I suggest that you determine the maximum amount of available oxygen, then choose the largest, most efficient torch you can run with that amount of oxygen.

If you are on bottles, it becomes a question of time vs money. Which do you wish to spend?

Malcolm