A project of ours is specifying blackened steel for some of the steel in our building. The issue is that the touch up material used for field touch up after welding is highly toxic, despite having 0 VOCs. I don't think this falls under the scope of any LEED credits but our concern is for the workers who have to apply this nasty stuff - has anyone had used the Instablack 333 or Presto Black Gel or have any alternative products they'd suggest?