How to make Dry sift Hash (A.K.A Kief)
Flat screening removes the trichomes by rubbing the skuff over a fine steel or silk screen. This is a very simple process but the quality of hash is very dependent on the skill and patience of the maker. The principle behind this method is that the trichome heads are of a fairly consistent size, so that when applied to a mesh of the appropriate size, the trichome heads will pass through but other plant matter will be left behind.
You'll need a flat screen. Screens can be bought from printing supply shops for $10 to $30, depending on size, or you can make your own. To make your own, fasten four pieces of wood together to form a frame, then glue screening to the bottom. Small hole screens are best, between 125-137 lines per inch.
You'll also need a piece of glass or a mirror to collect trichomes, a credit card or something similar for pushing, and of course skuff.
Skuff used for flat screening should be dry, but not too dry. If your skuff is really crumbly, too much vegetable matter will pass through the screen.
Put the screen on top of the mirror or piece of glass and place the skuff on the screen. Using the card, gently push your skuff back and forth across the screen. Using minimal pressure on the skuff produces the best hash. The first layer of powder that comes through will be the most pure and potent.
Because the skuff must be in contact with the screen to remove the glands, it is almost impossible to get a pure hash through flat screening. For this reason, some people choose to pass their skuff through an old pair of panty hose or a screen with slightly larger holes first. This produces a mixture of trichomes and small bits of plant material, which is then transferred onto the small holed screen. The screen then only needs to be tapped to let the glands fall through and be separated from the vegetation.