Mortar/ grinding sulfur, peppers, coffee beans

I have all the items need for the potion, but I cant empty the mortar and keep the item in my inventory. The potion is to copy items, Seems like I need two more mortars? Help

Go to the potion making machine.Pour in the required liquid and then empty the mortar. Grind the next ingredient. It will wait for the next ingredients as long as you pour the correct liquid first.