I have a student that refuses to blow. I know he's got the lungs, but he cannot seem to shake the timidity that he has. I thought the problem was the fact that he was playing on a 6 1/2AL mouthpiece as a beginner, and quickly switched him to a 12c. However, this does not seem to have remedied the problem. Does anyone have any suggestions for teaching this? Thank you.

There are a lot of students that have that timidity issue.
I do two things that seem to help.

1st - I have them play everything on their lesson sheet at FF, as loud as they can. Everything during the week is supposed to be practiced as loud as they can. I tell them loud is more important than hitting the correct notes. I let their parents know that everything is supposed to be played as loud as possible (if the parents aren't told by you they won't believe the student if the student tells them). I think their muscles just don't know how to do it sometimes. Also, when they have been practicing for years at mp and mf, when they switch to loud they will miss notes until they get use to it, so while I am getting them to go louder I tell them to not worry about the notes. Tell them not to even listen for the notes - just play everything loud.

2nd - Enunciation. I show my students the difference between talking with their friends and family, and public speaking and acting. Part of their assignment for the week is to speak clearly and succintly at all times as though they are reading a poem or story in a public venue. They are to be decisive, and clear. I also ask them not to use the words (yeah, I dunno, maybe, sure, kinda, ) they need to use decisive words like Yes or No and they need to be spoken with conviction. What this speaking does is change their posture without them knowing it is changing their posture which will allow for a more uninterrupted flow of air. And it trains the brain to make decisions.

These two seem to work really well for my students.

i agree with john 100%. you can also try the dallor on the wall exersise. if you don't know what that is, you just hold a dallor up against a wall, have them stand with there face realy close to it. move your hand and have them hold the dallor on the wall just by blowing on it. it seems like it would be easy but they will soon learn how little air they are really using

I had the same problem for a while with myself.

Best suggestion I can give just as a student is get them to buy the Arban's trombone book. It's got a lot of really advanced stuff that will probably make them need a change of underwear when they see it, but it has some very valuable exercises for beginners too. Just start on the first page and have the goal be to play it as full and loud as you can. Tell them that they should be breathing between every measure. If they're not breathing between every measure, they're not playing with enough air and not big enough.

Just flip through the book and you can find plenty of easier exercises if this is a rather new student that they should be able to play or at least get through without too much trouble.

Goal on all of them: Use as much air as you can. Fill the trombone.