Different recipes will call for different blanching times, but the key is to be quick. With blanching, time is measured in terms of seconds rather than minutes! Typical blanching times range from 30 to 60 seconds. This is a clue that blanching is more of a prep technique than a cooking technique. Blanching should not really ‘cook’ your food.
A crucial part of refreshing is that you don't want to let the food sit in the ice bath for too long, or it will start to absorb water and become soggy. What you want to do instead is just let it chill until the food is no longer warm, then drain it thoroughly. Either store or set it aside for whatever the next step of your recipe is. A common use is to soften vegetables so that they can be quickly cooked over high heat, like in a stir-fry.
Boiling & Simmering
While neither simmering nor boiling is difficult, both are essential techniques used to prepare everything from noodles to stews. They're really degrees of the same thing, but the effect each has on food is profoundly different. For most purposes, a simmer is a stage when the water is in motion but only a few bubbles break the surface, being held back by the water's surface tension. Boiling refers to the liquid that's in full motion, with bubbles rapidly rising to the surface. Water boils at 100 degrees Celsius.
In the case of noodles, boiling water helps keep the food in motion, promoting even cooking and preventing sticking. Boiling causes speedy evaporation, a useful tool for reducing and thickening sauces, where the volume of liquid decreases and flavours are concentrated.
Simmering is a cooking method more gentle than boiling. It refers to cooking food in liquid (or cooking just the liquid itself) at a temperature slightly below boiling point. It can be trickier compared to boiling because it requires careful regulation of temperature so that the surface of the liquid shimmers, with a bubble coming up every few seconds.