resist water has made it popular with marine aquarium hobbyists for fragmenting corals. The cut branches of hard corals, such as Acropora, can be glued to a piece of live rock (harvested reef coral) or Milliput (epoxy putty) to allow the new fragment to grow out. It is safe to use directly in the tank, unlike silicone which must be cured to be safe. However, as a class of adhesives, traditional cyanoacrylates are classified as having "weak" resistance to both moisture and heat although the inclusion of phthalic anhydride reportedly counteracts both of these characteristics. Cyanoacrylate glue is also used frequently in aquascaping both freshwater and marine aquariums for the purpose of securing the rhizomes of live plants to pieces of wood or stone. Thin cyanoacrylate glue has application in woodworking. It can be used as a fast-drying, glossy finish. An oil, such as boiled linseed oil, may be used to control the rate at which the cyanoacrylate cures. Cyanoacrylate glue is also used in combination with sawdust (from a saw or sanding) to fill voids and cracks. These repair methods are used on piano soundboards, wood instruments, and wood furniture. Cyanoacrylate glue is also used in the finishing of pen blanks (wooden blanks for turning pens) that have been turned on a lathe by applying multiple thin layers to build up a hard, clear finish that can then be sanded and polished to a glossy finish. Some hobby applications call for cyanoacrylate glue mixed with inorganic fillers such as baking soda (sodium bicarbonate) and calcium oxide. Cyanoacrylate is used in archery to glue fletching to arrow shafts. Some special fletching glues are primarily cyanoacrylate repackaged in special fletching glue kits. Such tubes often have a long, thin metal nozzle for improved precision in applying the glue to the base of the fletching and to ensure secure bonding to the arrow shaft. Safety issues Skin injuries Cyanoacrylate adhesives may adhere to body parts, and injuries may occur when parts of the skin are torn off. Without force, however, the glue will spontaneously separate from the skin in time (up to four days). Separation can be accelerated by applying vegetable oil near, on, and around the glue. In the case of glued eyelids, especially if it has contacted the eyeball, medical experts are indicated. Toxicity Heating causes depolymerization of the cured polymers producing gaseous products that are highly irritating.. They are