How does a scale show pressing progress?
Whether a pressed flower is dry is easier to read on a scale than by touch. The solid matter inside the petal does not disappear while it dries, only the water does, so comparing the first weight with the current one turns the remaining moisture into a number. Enter the weight at pressing in grams (a 0.01 g jewelry or kitchen scale works; ounces are shown alongside) and the starting and target moisture, then add the weight you measured today.
The method is a mass balance. The dry solids weight is the starting weight times one minus the starting moisture, and the target weight divides those solids by one minus the target moisture. The current moisture divides the solids by the current weight and subtracts from one, and progress divides the weight already lost by the weight that has to be lost in total. Every comparison uses the same decimals shown on screen.
The starting moisture of a flower varies by species, by specimen and by when it was cut, and no official source publishes a figure, so it is yours to enter. If you do not know it, dry one flower of the same kind completely and work backwards from that weight. Predicting how many days pressing takes is not covered here, nor is judging discoloration, mold or preservation treatment.
Frequently Asked Questions
Dry one flower of the same kind completely, treat that weight as the solids and work backwards. No official table of species moisture levels exists.
It means the weight for the target moisture you entered has been reached. Entering a lower target lowers the target weight as well.
No. Drying time depends on humidity and how often the blotting paper is changed, so this page reports only what the current weight shows.