Reusing EffectsComposer result

[Rakasis]

I have an effectsComposer creating a result that is heavy in white. 

 

var composer = new THREE.EffectComposer(renderer);

var renderPass = new THREE.RenderPass(shaderHeavyScene, camera);

composer.render(delta)

 

In the same project I have a material and scene with with a second image loaded into it. 

 

When I replace: composer.render(delta);

with: renderer.render( secondImageScene, camera );

 

I can see my secondary image loaded into the three.js canvas.  

 

My plan was to multiply the white heavy image of effectsComposer over the secondImageScene. (Revealing secondImageScene through the white)

 

My question is this: How would I go about multiplying the end result of the effectsComposer overtop of secondImageScene?