Over the years I've soldered several remodels worth of copper pipe (water and hydronic heat). I'm not great, but I get the job done, until I have to add a brass fitting. For some reason, I can't get the solder to suck into the joint. Does soldering a brass fittings to copper pipe require a special technique?
Very Important Make sure the joint is really clean when you solder - so use emery cloth or sandpaper to remove any contaminants in your solder joint and flux the joint prior to heating. I like to wipe the joint with acetone before applying flux but I'm anal retentive like that.
Also you might want to consider using MAPP gas vs propane - those brass fittings take a lot of heat before you will get solder to flow into the joint.
I just had the same experience. What i figured out was, whereas they say to concentrate your heat on one side of the fitting until it is hot enough for the solder to flow for copper, i had to heat all around the fitting for brass. Once I did that it flowed just like copper. Like the pros are saying, it took more heat for it to flow properly with the brass.
I found (after a couple of bad jobs) that if your solder is sitting in a toolbox it oxidizes and gets dirt on the roll you will have problems. It will have major problems sticking, and you will be there for hours, -- even copper to copper. Dirty/oxidized solder will make for a lot of frustration in the field, hold you up on a job, and just plain out make you feel inadequate in your skills (when it has nothing to do with you). I now double-bag my solder and keep it totally clean from now on. The comments on flux, brush, and fitting to be clean are true too. It is a game changer in keeping fresh/clean solder. I learned by being embarrassed on a couple of jobs and somehow figured it out. I had to walk away from one job and told her I did not know what it was (on solder not adhering/sticking to a hose bib change out), and to call another tech/plumber. I felt really bad. Repair is a tough game sometimes.