Pattern Modifer – Fluid replacement

[effleurager]

It's unclear how to modify fluid pattern ingredients as the amount set for the fluid is always 1 bucket, and there does not appear to be a way to set the exact amount. Also, is the intention to support replacing one fluid for another using the same volume, or should each amount be set?

Lastly, is the result of replacing an ingredient with nothing meant to be a no-op?