Well, it turns out that rice is like a sponge - it absorbs water like crazy. And, if you don't use enough water, your rice can end up all dry and crumbly. On the other hand, if you use too much water, you'll end up with a soggy mess.
So, the 4:2 ratio is kind of like the Goldilocks of rice cooking - it's just right. But, what if you're using a different type of rice? Does that change things? Like, what if you're using jasmine rice or brown rice?
As it turns out, different types of rice have different absorption rates. So, you might need to adjust the water ratio depending on the type of rice you're using. For example, brown rice usually requires a bit more water than white rice.
Cuisinart Rice To Water Ratio at Rory Barbour blog
