Liquid Yeast

With the white lab yeasts, can one open it and use part of it and store it for a later use or is it better suited to use it all at once?

You probably could but what i would do is spit it into 2 starters…step up the one you are gonna use and store the other one for future use…but i think its best to use it all at once…using half a vial would result in the need to step it up quite a few times or making a large start from the gate

What is the size of the batch 1 gallon? If its five gallons you’re way way way under pitching. Look up making a starter and do that.

+1 on making starters and it is not enough for 5 gallons. I would be afraid of infecting it or introducing wild yeast.

A few years ago when I was brewing more often I used a White Labs to make a starter and refilled the tube before I pitched it. It worked well.