Poppyseed oil (also poppy seed oil or poppy oil) is oil extracted from the seeds of the opium poppy (Papaver somniferum).
The whole seeds of the poppy plant are edible and non-toxic, and have been used for various culinary purposes (particularly baking) since ancient times. Similarly, poppyseed oil has no narcotic properties and is sometimes used as a cooking oil; it is also used for moisturizing skin. Its primary use, however, is in the manufacture of paints, varnishes, and soaps.
In oil painting, linseed oil remains the most popular oil for binding pigment, thinning paint, and varnishing finished paintings. Walnut oil and poppyseed oil are also favored by oil painters, though each of the three oils is used for a different purpose. While poppyseed oil does not leave the unwanted yellow tint for which linseed oil is known, it is much weaker in the test of time than the contemporary linseed oil.
Because poppyseed oil dries much more slowly (5-7 days) than linseed oil (3-5 days), "fat over lean" rules apply, poppyseed oil falling on the "fat" side. Poppyseed oil should never be used for a ground layer of a painting, and one should avoid painting linseed oil over a layer of poppyseed oil; this will likely cause cracks and peeling as the upper layer dries first, making the "lean" layer vulnerable to contraction when the "fat" layer dries underneath it.