The Mortar holds two separate 1000 mB tanks, in the same way Create's Basin does.

• The input tank is the one you fill from the outside, with a bucket or a pipe, and the only one a fluid_ingredient is ever drawn from.
• The output tank receives fluid_results. It can be drained from the outside but never filled.

A recipe only runs if its entire fluid result fits in the output tank. Once that tank is full, the Mortar simply stops accepting the recipe. Empty the output tank and it picks straight back up.

Both fluid_ingredient and fluid_results are optional on every Mortar Grinding and Mortar Mixing recipe. If a recipe produces only fluid, results can be left out entirely.