The secret of barbecue is heat, time, and smoke. The secret of great barbecue and successful smoking is airflow. You need to bring smoke to the meat but you can't hold it there for too long. Smoke that becomes too heavy or stays for too long creates a substance called creosote.
Creosote is a thick, oily substance left over by fire. It not only causes foods to become bitter but it numbs the tongue when you eat it. If you have ever left a plate of barbecue with a numb feeling on the tongue it is because of creosote build up on the meat.
To eliminate creosote you need to start with a clean smoker. A dirty, crusted smoker will help produce creosote. Then you need to make sure that you have proper airflow. If you have a small water smoker there probably isn't a lot you can do to hold in smoke or control how much gets away. If your smoker has a vent then you need to make sure that enough smoke is getting out to prevent it from building up.
Testing for Creosote
One way to test for creosote is to hold a glass of ice water in the stream of smoke coming out of your smoker. If you notice black specks on the glass after a minute or so then you don't have enough ventilation. Open the vents more to let more air travel through the smoker. If you have a vertical water smoker without vents then remove the lid for a minute to let the smoke escape. Once you have noticed the creosote it is time to stop adding wood to the fire. Reduce the smoke production, at least for a little while. At this point, you might want to wrap the meat in foil and allow it to continue cooking without being exposed to more smoke.
Another way to test for creosote is by tasting the meat. Of course, this is a little late in the process, but doing a test run of the smoker with an inexpensive piece of meat will help to diagnose the problem. Take a piece of the darkest meat along the surface and put it in your mouth. Let it sit on the tongue for a little bit. Does it taste bitter? Does your tongue feel a little numb? You will usually notice the numbness before you taste the bitterness.
Once the chemical reaction takes place the surface of smoked meats is pretty much ruined. The only hope you have left is to carve off the blackened edges and eat the interior of the meat. This is pretty much impossible with ribs but can be done with brisket and pork roasts.