Indicators change color gradually across a pH range, and it is common for one of the indicator's forms to be colorless. Since indicators are weak acids, care should be taken to avoid adding too much indicator (more than 3 to 4 drops per 100-mL) to a solution of acid or base.
Roast your pork shoulder in the oven at 350 degrees F for 30 to 35 minutes per pound for a nice slicing roast. At this temperature, a 6-pound pork shoulder will require 3 to 3 1/2 hours to roast. Check for doneness by placing a meat thermometer into the roast at the thickest point. Be careful not to touch the bone.
Place the roast fat-side up in a shallow roasting pan. If you have a wire rack, set it in the pan and set the roast on it. Toss a few cups of mirepoix around the roast and place it in the oven on the center rack. Sear the pork roast until it develops a dark brown color, about 10 to 12 minutes. Lower the temperature to 325 F. Roast pork loin for 22 minutes per pound; roast pork shoulder and leg for 25 minutes per pound. Cover the roast with aluminum foil if you see the top getting too brown. Pork roasts measure 145 F in the center when fully cooked.