Mastic is dissolved in alcohol to glaze Greek pastries and to flavor the local Retsina wine. The tears can be melted (96 Celsius/204 Fahrenheit) and dissolved into turpentine to produce a transparent straw-colored varnish. Some writers claim it can be dissolved in unheated turpentine, but unless you heat mastic, it will not dissolve perfectly. Mastic is a natural product and it contains impurities (pieces of bark, dirt and insects) which must be filtered out in order to make high quality varnish. CAUTION: at 34 Celsius (93 Fahrenheit), the flash point of turpentine is well below the melting point of mastic tears. Do not attempt to make the varnish over an open flame or electric burner. Only use a vessel having an enclosed heating element. Always keep a fire extinguisher nearby. Jacques Callot, the French engraver and etcher, was an important innovator in both the technique and subject matter of printmaking. As a court printmaker for the Medici in Florence from 1612 to 1621, he developed a hard etching medium (a varnish made of linseed oil and mastic) which allowed great fineness and detail. This innovation facilitated the work of the great etchers of the 1600s, such as Rembrandt. Mastic dissolved into turpentine produces a superior picture varnish to damar in that it flows out to a clear and glossy coating with greater ease. Applying any picture varnish in damp weather risks "bloom," which is a whitish patch in the varnish. If that happens, the varnish must be removed and applied in a dry environment. Dissolving one part of mastic tears into two parts of turpentine makes the picture varnish. Mixed with linseed oil, mastic varnish thickens into a jelly called megilp. Megilp has been implicated in many of the failures of 19th century paintings to survive intact. Megilp should not be confused with Maroger Medium, which is a combination of Black Oil (litharge cooked into solution with linseed oil) and Double Mastic varnish. After more than thirty years of testing we have found that, properly used, Maroger's Medium is much more durable than megilp and many commonly used painting mediums. Mastic tears must be melted or they will not completely mix with turpentine. This can be a tricky process because the melting point of the mastic tears is well beyond the flash point of turpentine. Keep a fire extinguisher handy and avoid open flames or sparks (no smoking). After the tears have dissolved in the turpentine and is still warm, pour the varnish through filter paper to remove the bark, dirt and debris. After standing for a day or two, you may notice a waxy residue at the bottom of the container. Simply decant the varnish to another container, leaving that residue behind. If all of this sounds like too much work, Studio Products makes a Double Mastic varnish which has been filtered twice with the wax removed.