i have been using blend of cotton/polyester thread. i ran out of the spool and put a new spool on and sewed some pieces together before i realized that it is 100% cotton. my bobbin thread still has the blended thread. i know that the cotton thread shrinks. is this going to be a big problem if i keep using this thread with or without the bobbin being mixed? and should i make sure that i am using all of the same thread on the project. so i guess should i take out what i have done and get some of the same thread that i started with?