Growling and hissing

We performed an experiment today and Tiger and Karen's cat, Shadow were the subjects. I had this great idea of trying to see if the two cats would get along so that when we left on our GA trip, we could leave Tiger with Karen and save over $100. Well, we packed him up in his pet taxi (which he's almost outgrown) and made our way to Karen's house. We got there and at first, I didn't let Tiger out of the cage. Shadow saw that we had a visitor. She wasn't so sure about it and she hesitated coming over to us. I finally opened the cage for Tiger to come out and that's when the fireworks started. There was growling and hissing and tensed up cat bodies. Tiger started walking around but I was scared that wouldn't go too well because I knew the other cat would want to defend her own territory. He went into their laundry room where the litter box was and I knew it was probably time for him to use it. He had been in the car for a long while and I didn't know for sure if he had to go or not. He first checked out behind the dryer but I pulled him out of that and guided him to the litter box. He seemed interested. He took a sniff or two and perched himself on the lip of the box and then let out a hiss as if he thought somebody had been using HIS box. He got in finally and actually went number 1 for a long time. Man, was I glad he went in there instead of in the pet taxi and in the car. He got out and Shadow saw that he had been in there and was headed towards the laundry room to probably try and rip him a new one. I quickly saw what was coming and before she could come in there with him, I pushed the laundry room door closed to a crack. Shadow wanted in of course and she was not going to stop at anything. That is the strongest little cat I've EVER seen! She was pushing herself against the door and I was actually having to keep some force against the door because she was really pushing!! I decided she wasn't gonna stop so I grabbed Tiger up in my arms so he'd be protected because she has front claws and of course, Tiger doesn't. I just got too stressed that they were going to have this huge cat fight, so I put Tiger back in his cage. Pretty soon, Tiger started hissing and growling whenever Shadow came within his line of vision. They both were hissing and growling before long and it was like they were having a conversation between each other because the growling would alternate. Finally Shadow had enough and went into another room. I decided it was time to take Tiger home because it just wasn't working. I was happy that we had at least tried this to see how it would work instead of only dropping Tiger off at Karen's place and then leaving. I'm sure she appreciated it too. It could've been a disasterous 2 weeks! Needless to say, we're leaving Tiger at the boarding place where he'll be in his own cage, with his own litter box and food. He won't have to share anything. haha!