Stepped out on the back porch (Aransas Ave. & Barlow St.) looked north in the sky (looking for birds) and observed what I first thought was a silver or white balloon or possibly a plastic bag floating skyward. Noticed the object moved more slowly than a balloon or plastic bag caught in a breeze would and it seemed to be moving with a purpose of direction. It also seemed to be flipping/spinning or pulsating. I watched the object move slowly upwards and to the NE/NNE at slow speed. I scanned the area for other aircraft and could see none (unusual beacuse I live in the flight path of the International Airport). Thought about calling the Airport but I decided to see how long I could watch this thing, took about 10 minutes before it vanished from sight totally. Winds were light out of the south and there were a few clouds.