Niello question

Hi all , I have just tried to make up some niello and have struck a
problem . I melted 2gms silver , 4 gms copper and 6gms lead , pored
it into about 4 teaspoons of sulphur , after cooling , I remelted it
with another teaspoon of sulpher , then pored it out . When I tried
to break it up , I found it is still mostly a metal - it just deforms
. Am I not using enough sulphur ? I stirred it while molten with a
wooden dowel and just pored it into powdered sulphur , should I have
melted the sulphur first , maybe by heating the outside of the
crucible with a LPG torch ? A ny help you can give would be
greatly appreciated ! Philip Wells in sunny , cold Nelson @Wellsie