Iron particulates of micron-submicron size are pyrophoric (may spontaneously ignite on contact with air). Care should be exercised with this particularly reactive form of iron. Iron needs to be protected before use in pyrotechnic compositions. Otherwise it will corrode and render the composition useless or even dangerous. Iron containing compositions are generally best kept dry and not bound with water soluble binders. Iron can be coated with linseed or tung oil. The latter was used in ancient China (and may still be used today). Linseed is very convenient to use and easy to obtain. Blackpowder-like compositions (ie Charcoal/sulfur/saltpeter based) with added metal, such as they are often used in fountains, are more sensitive than the composition without added metal. Extra caution, especially when pressing or ramming, should be excersised.