lead free soft soldering

I've done a little silver soldering with copper pipes and fittings using MAPP gas with success. I thought I'd have a go with the lead free (tin) soft soldering, however, I can't get the solder to flow into the joint and it just rolls off the pipe. Do I need a special lead free soft solder flux and how much heat should I apply?...I get the joint glowing.

Two things straight off.

Yes you need flux

and

if the joint is glowing, it's too hot and you will end up burning the solder

Thanks DJ, How do you know when you've applied enough heat using a MAPP gas torch?

Every now and then remove the flame and touch solder to copper and see if it melts the solder. You don't need a lot of heat, solder doesn't like high heat as it will get brittle.

Generally I just heat till it just starts to run and keep the flame away till heat starts dieing and reheat till just starts running again

Oh, and don't trust soft solder for copper pipes carrying water where the joins will be concealed when finished.

Mick

Why waste your time with soft solder when you can silver solder? Much better job and wont break like soft solder does.