I have a question that is going to sound pretty basic. I have a small gas welder that I have been using for small projects around the house. I learned to weld back in high school, but that has been quite a while ago. I cant remember how to fine tune the flame, or what is supposed to look like. After I turn on the acetylene and mix in the oxygen, when the two cones develop to get a neutral flame do I join the two together or keep them as two separate cones inside of each other. I have been trying to find examples on You Tube, but everything I've seen is hard to see the actual flame due to the brightness. People I guess only use cell phone cameras or other things that cant take the intense brightness. The problem I am having is oxidizing the metal, and having it look bubbly afterwards and being brittle.

 

If you are using mild steel welding rods you would use a neutral flame.
When the outer flame is longer than the inner flame, reduce the acetylene until the outer flame is equal to the inner flame.
If you continue to decrease the acetylene you will have an oxidizing flame which is hotter and could produce the results you are seeing.

A carbonizing flame where the outer come is a bit longer than the inner flame is cooler and normally used for brazing with bronze and similar rod.

Other causes for bad welds are unclean or rusty metal, bad or the wrong type of welding rod or base metal not being mild steel or compatible with the rod you are using.