How to stop biting

[bright sparks]

Honestly if it isn't out of temper then it would just be a case of shadowing and constantly doing behaviour modification via negative reinforcement....tha t is what I would do. Putting in a playpen or highchair when you leave the room is your best bet too as you have been doing. Maybe rather than time outs, having him in a highchair in the room for a longer period of time as a repercussion for biting would mean he can see all the fun happening but can not join in, and if this is constantly your response to him trying to bite or actually biting then maybe he will be less likely. Unfortunately his age really doesn't help in the communication and comprehension of the whole situation. Good Luck