Your times will be affected by the power of your microwave. Always start with imperfect flowers/foliage. This will allow you to test times without ruining your best specimens. We recommend starting with short times such as 25 seconds for the first burst, until you are assured you can use longer timed bursts without burning your flowers, liners and pads. Always wipe the platens between bursts. When little moisture accumulates on the platens, your flowers will be dry or almost dry. Succeeding bursts after the first should generally be of shorter duration.
Lift corner of the pad/liner to check your flowers. They will feel papery when dry, should be somewhat stiff and will not droop when lifted. Flowers petals which are not dry enough will pucker and center moisture may leach into (and discolor) the petals. Keep log for each type of flower you press. This will give you a starting guide for the next time you press the same flower. The pressing time for the same flower may vary from one day to the next due to changing moisture content. After you have had a bit of practice you will better be able to judge pressing times and you will be able to tell quite easily if more pressing is needed.