Lead is a through drier & is always used as active or top drier. It promotes hard & through drying throughout the film. When lead is used with cobalt or Calcium Octoate it is advisable to add Calcium Octoate first to eliminate possibility of Lead Octoate to react with unreacted pthalic anhydride of alkyd resin, which could form Lead Pthalate. In exterior paints & floor finishes Lead is used along with Manganese to produce tough & hard film. It is also used in Polyurethane finishes as auxiliary drier. Lead drier improves the drying time of double boiled linseed oil.