Unreal Engine Blendables Blend Weigth Tutorial

When setting up PostProcessSettings Blend Weight doesn't affect on PostProcess material appearance by default. There is two solutions.

The first is simply to create your own Blendable in c++ or Blueprint and implement desired functionality as its suggested by Epic (https://docs.unrealengine.com/latest/INT/Engine/Rendering/PostProcessEffects/Blendables/index.html)

The second is to set-up right settings in master material and material instances of PPM. I've found that Blend Weight default behaviour is performing interpolation between master and instance material parameter values. It's a key to this solution. When Developing a shader, it is necessary to pick out all parameters that changing shader appearance and set its values in master material so master material doesnt
affect the screen. Then create a material instance and setup it as you want it looks when material is full-powered. Now its done. When setting up PostProcessSettings, use material instance and change weight value as you like.

This is settings of Master material I've created as example. You can see that intensity parameter is set to 0 by defaul,t so this shader doesn't affect on scene color.

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Example Tint Material

Then I created Material Instance and set intensity to 1. I set the Instance in PostProcess volume to test Blend Weight. 

Instance Settings