I inadvertently used two layers of batting when I did a machine embroidered quilt block set. The machine embroidery process used a piece of batting for each block, then when I had it longarmed, it was sandwiched with another. It’s a terrible quilt, very stiff and heavy. My son never uses it, it just sits on the edge of his bed as a decoration basically. Thankfully, I’ve learned as I’ve gone along quilting and won’t make that mistake on his next quilt. I’ll make new mistakes on this one.