The shake: Is it hard as fuck to shake your grains apart during the shake? Like, do you have to smash that jar so hard that it almost hurts your hand (or does hurt your hand)? If it's that tenacious then it's likely contaminated.
Clean spawn should be easy to shake apart, bacterial spawn will cling tenaciously and will be difficult to shake.
![](https://i.ytimg.com/vi/hV0iqtYFNDE/maxresdefault.jpg)