When should i use a mask behind a FAB button?

Question

Right now at work we are making this amazing feature (for a webApp) but i don't know WHEN its correct to use a "mask" Behind the FAB after it gets TAP/CLICKED because in the guide they say nothing about it, all i know is:

1. It would be better to improve readability
2. I have seen it (The mask) in other google apps
3. Pinterest use this behind-mask every time you click on a "PIN"

Below ill link you the Material Design Guide:

https://material.google.com/components/buttons-floating-action-button.html#buttons-floating-action-button-behavior

Answer 1

This question is unrelated to FAB, you use a scrim whenever appropriate, specifically when you load a modal, dialog or a new sheet of material. Whether it's launched by a FAB, a link or a button, is irrelevant.

If you want an example of this behavior triggered by a FAB, take a look to https://material-design.storage.googleapis.com/publish/material_v_8/material_ext_publish/0B8v7jImPsDi-Mk9EVk5DRVN1cmc/components-buttons-fab-transition_card_01.mp4

and

https://material-design.storage.googleapis.com/publish/material_v_8/material_ext_publish/0B8v7jImPsDi-V2EwR1lqcHFoVVk/components-buttons-fab-transition_card_02.mp4

All in all, it will also depend on your needs, not everything needs a FAB, not everything needs a pop-up or modal, so this is a generic answer to your specific question