Interfacing (i.e. Pellon or Peltex): Actually it's pretty good stuff, but I have only seen it in white. If you bead fairly close together, it's not a big deal. It comes on the bolt, so you can get great lengths and cut interesting shapes and patterns.
Craft felt: I didn't have good luck with this. Pilled, shredded and was uneven to work on.
Interfacing with an Iron-on Canvas: I used this with the Taj Mahal. Man, oh man, was this a bear to bead through!! Interfacing was fine, but the iron-on that I printed the outline on was so hard to get the needle through. Maybe that is why it took years to finish. I will not recommend this to anyone!Lacey's Stiff Stuff: Decent stuff, but never felt the best for me. Many people do love it and swear by it - we all have what we love. It did shred a little, can be dyed to other colors, made larger by placing the edges next to each other and sewing together but is a decent product.
Nicole's Bead Backing: This is my hands down favorite bead embroidery product to use. It doesn't pill, minimal shredding, comes in 16 colors, takes iron-on transfer pencil, stamps and more. My silver tiara is actually on the green bead backing, because I was going to use a sample and then just decided to go for it.
Bead Foundation by BeadSmith: I just used this recently for a project and I don't care for it at all. It feels thin, flimsy and shreds. I think it's obvious that I didn't like it.These are just my opinions, you may love a product that I don't care for - which is perfectly fine. There is room for all sorts of opinions on different products.
