Ruston Hornsby starter wicks

Hope you knowledgeable folk out there can help a friend of mine in the US. He has a Ruston which requires starter wicks to get it running. He has been unable to source any out there and has tried making his own from saltpeter, but is not sure whether he has used the correct formula! Does anyone have any knowledge of these, are they available to buy in the UK? I have little knowledge in this area, but I'm sure someone will know the answer. Many thanks in anticipation. Mark