Temperature is the most important factor. The difference between those stored in the refrigerator and those stored at room temperature is very obvious. Generally, the viscosity of bagged milk is above 70, generally not more than 90. However, barrels and cups are relatively thick, generally above 120. But I'm talking about the kinematic viscosity at standard 20 degrees. The higher the temperature, the thinner the yogurt.

Fermentation process, which is also an important factor, and the quality of milk itself.

I hope I can help you.