Edge effects on almost completely transparent objects I've got a semi-transparent outer block, and two semi-transparent inner blocks. I'm trying to animate the inner blocks fading out by bringing the transparency alpha to zero. I'm using Blender Internal.

My model looks like this:



These are wax blocks, with objects embedded inside. First, the small inner blocks are created separately as 2x1 blocks. Then they're placed next to each other to make a large 2x2 block. Once the outer wax is in place (a boolean modifier/plane reveals the outer wax) the inner wax should fade away, "melting" as it's replaced by the the outer wax. 

The problem I'm having is that the sharp edges of the inner wax don't fade away as alpha approaches zero. My guess about what's going on is the amount of light that's reflected off the inner faces is unaffected by their material's transparency.

Effectively, I don't like the discontinuity between when alpha is very small, and when alpha is zero. Here's is the difference between the inner blocks transparency alpha at 0.001, and 0.000:
Turns out the problem goes away if I switched the transparency of the outer block from raytraced to z-transparency.