I am a comeback player who had sold my horn to friends for their son. When I decided to come back, I bought my horn back. Unfortunately, the 2nd valve slide had been pushed into the valve casing, causing the valve to hang up. The only to repair it was to lap it. I had to take the horn back to the repairman twice because the valve worked fine when the horn was cold, but as soon as it warmed up, the metal seemed to expand and the valve would hang up. However, the problem was never completely solved, and I was apprehensive to lap the valve any more. My trumpet teacher use to build horns for callechio (sp?) years ago, and he said when they had a stuborn sticky valve problem they would soak the valve in a liquid Ivory dish soap solution and let them air dry before putting them in the horn. Well, I tried it, and it worked like a charm!!!
The valve works like new and hasn't hung up or been sluggish once.