I'm having a bit of confusion about this particular topic and was hoping someone could clear this up.
Refinement gives Specialization bonuses that must be structured in the same manner as skills. On YS249 it says (in bold no less) that Specialization bonuses do not stack.
Here's the question:
Does this mean that you can not take a refinement and gain a bonus in something you already have a specialization for? as they wouldn't stack and thus would be useless. Such as if you already have a +1 power specialization from the free evocation focus and then try to add +1 power and +1 control to the same element, would you end up with just +1 power and +1 control because the power bonuses don't stack?
If it's the case that they don't stack like that, would you then have to take another refinement to get +2 power, which would trump the +1 power already established and would be used instead? If so, how do you get more than +2 bonus on anything given that refinement can only give you 2 +1s and you can't stack them on top of any existing specializations?
You can stack them. You can't use more then one at a time though. Say you have a lot of refinement, and end up with specialization like this:
Control +1 Spirit, +2 Fire, +3 Earth
Power +1 Spirit, +2 Fire, +3 Earth
You have to have a one, in order to have a two. And a two in order to have a three, etc.
Now, say you have a volcano spell. You could use earth or fire for it, right? Well, you have to choose. You can't use both the Fire and Earth power/control, you can use either the Fire OR the Earth. You can't stack two different kinds of specialization in a spell. That doesn't include foci, which stack on top of specialization.
I learned this the hard way, when I had a air/water wizard who would make a thunderstorm as a manuever. I tried to add both specialization, which isn't allowed. It keeps all of those specialization from being spent in the same spell.
Here is what it has to look like, in the manner of skill stacking.
+3 O
+2 O O
+1 O O O
Fire, Earth, Spirit Power