ALUMINIUM GLAZING BARS

We have an old aluminium greenhouse that was about to be scrapped,I am trying to restore it to its former glory and put it to use,problem is the glazing bars are full of old putty which is proving very difficult to remove has anyone come accross this problem and if so what is the best way of getting rid of this extremely hard putty? ,obviously the bars will have to be stripped right back to there original state before I can attempt to reglaze,any sugestions please.  

Try a blowtorch which may soften it enough.  It depends on the type of putty, but most stuff bought over the last 30 years will have synthetic materials in it which should turn a bit softer under heat.  A canned-gas (usually Butane) blowtorch won't produce a flame hot enough to damage the aluminium.

Or use a hot air paint-stripping blower - a bit less dangerous.