BeerBorg

I washed yeast and stored in water that had been boiled and cooled. I filled the mason jars to the brim.
It's been sitting in my refrigerator for 4-5 months. Can I make a starter and step this yeast up and have a healthy yeast to pitch?

I have ECY-10 and London 1968.

Should I brew a small test batch to see if the yeast is viable after I step the yeast up?

I believe if you start with an initial 500 ml starter at 1.020 and then step that into say... 1-1.5 liters of 1.030 you shoud be fine.

Along the way you should see activity if it's working.

I've used much older washed yeast without issue. But yes, a starter is mandatory.

I've also used much older yeast. I do the stir plate thingy a couple times to build up the viable yeasties tho.

All the correct information has been noted and said, so I'll move along.

Thanks guys!