Magnesium ribbon
From PyroGuide
Formula: Mg
Description: Magnesium ribbon is an element and a metal. It is silver coloured, very light and really quite reactive. It will react steadily with diluted acids and release hydrogen gas, it will also ignite whilst it is heated in air, emitting a quite brilliant white glow. This pyrotechnic material is usually supplied in a coiled ribbon form. In this form, the metal has an increased surface area and can be efficiently ignited and used in chemical reactions. It is used in pyrotechnics to produce certain firework mixtures or to ignite thermite reactions. Magnesium ribbon is one of the most common ways to ignite chemical reactions that require a higher temperature to ignite. The only downside to Magnesium ribbon is that it has a tendency to blow out in the wind, while having a relatively high ignition point.
Hazards: Magnesium metal and alloys are highly flammable in their pure form when molten, as a powder, or in ribbon form. Burning or molten magnesium metal reacts violently with water. Magnesium powder is an explosive hazard. One should wear safety glasses while working with magnesium. The bright white light (including ultraviolet) produced by burning magnesium can damage the eyes. Water should not be used to extinguish magnesium fires, because it can actually feed the fire. Carbon dioxide fire extinguishers should not be used either, because magnesium can burn in carbon dioxide. A Class D dry chemical fire extinguisher should be used if available, or else the fire should be covered with sand. An easy way to put out small metal fires is to place a polyethylene bag filled with dry sand on top of the fire. The heat of the fire will melt the bag and the sand will flow out onto the fire.
Sources: Making magnesium at home is very difficult. Magnesium can be bought in boating supply stores. It is used to prevent corrosion of a ships hull. For that purpose it is welded to the hull. The lower position of magnesium in the electrochemical series will make the magnesium corrode before the steel will. Making such a block of magnesium into a fine powder or ribbon will not be easy. Filing or cutting and ball milling may be tried. Ball milling of metals can be dangerous however since the metal can become pyrophoric. It also can be purchased via online pyrotechnic supply stores.
Places to Buy: If you live in the UK you can purchase Magnesium Ribbon from http://www.HobbyChemicals.co.uk