I am required to collect and press a variety of plants for a plant identification course that starts in the fall. The instructions say to change the inter-leafing paper after 24 hours, but it doesn't say how long they ultimately need to stay in the press. Can you help? Thanks in advance!
There's no definite answer to this, as it will depend on the temperature and humidity of the area in which you're drying the plants, and how many plants you're attempting to dry at one time. Anything that will increase the temperature and decrease the humidity will decrease the drying time. That said, I have to say the average drying time for me is 4-7 days. Something you can do to decrease the drying time yourself is to put the press near an air vent so that the air blows through the ventilators (through the holes in the corrugated carboard). If you have a room with a dehumidifier, that works too, espcially if the press is put where the warm, dry air blows through the ventilators. Another thing to try is to put a table lamp with a higher wattage incandescent light bulb on the floor, and put the press above it between two chairs so the heat from the light hits the press. Again, you want to place the press so the warm air rising flows through the ventilators. If nothing else, you can use a fan directed at the press. As a side tip, one the plants have been drying a day or two, tighten the straps on the press. The shrinkage of plants as they dry can allow the leaves to wrinkle in the press, and doesn't give you the smooth, flat results that look best.
It depends upon how many plants, humidity and if you are using gentle heat to speed the drying. In dry environments, thin tissues will dry in a few days. If you have high humidity and lots of fresh plant materials, it could take a lot longer. I would change the blotters every 24 hours if you have lots of plant material to press.
