Dangerous simmering - exploding liquid? (cheesemaking) This evening I attempted to make gjetost. I started with a gallon of milk and made mozzarella, then added a little dry milk, and made ricotta. Finally I was going to reduce the whey down into gjetost.

Once I got the whey reduced down to about 10% of its original volume, the simmering became incredibly... weird? Basically the bubbling became very erratic, and at least twice there was a sudden "BLUB" which sent showers of 230+ degree whey showering across the stovetop, also making a noticable SLAM when the pot physically jumped on the stovetop. After narrowly avoiding a bunch of burns twice, I moved the pot off the heat and walked away. I want to make the recipe but I'm not risking a trip to the hospital.

So, has anyone ever seen this happen? Why does it simmer so erratically and then have one big GLUB/bubble explosion in the center that is so violent? I've heard of things getting super heated, but that doesn't seem like it would apply here because it's not a completely pure liquid (there are some curds of albumin protein which would seem to be good origination sites).
Reducing whey to that level of concentration is going to create what is very likely to be a viscous, non-newtonian fluid.  That means its flow rate changes with sheer stress, much like ketchup does.

The heat at the bottom of the pan will slowly heat up water until a bubble of steam starts to form, and press against the remaining fluid.  At first, the pressure will not be enough to overcome the viscosity of the.. substance.  Eventually, the pressure will be sufficent that bubble ruptures, creating sheer in the fluid, which suddently becomes much mroe liquid.  And so you have a giant gloop.

See related:  Why does tomato sauce spatter more than other sauces?