Not to start the debate again about whether to prewash or not, but I always prewash and I serge the edges before hand. My darling dog, Annie, loves it. I just serge a huge stack and throw the finished one on the floor. She is delighted to have a cozy nest to lay on. Then I sort the colors and wash. Now I don't have to worry about big clumps of threads for me to cut off and screw up my fabric, which I am certainly very capable of doing quite well, thank you very much!