well I used a toothbrush and brushed the stuff off. The bottom was like one big sponge and had worked up onto the top of my gsp. It came off easily. I don't know if it was bad or not but I didn't like the look of it and figured it would continue to spread. Will be watching to see if it comes back. I actually decided to frag the gsp and put some in my bb fowler. I am hoping it will spread along the bottom glass.