There are numerous ways to decorate both metal and Plastic Caps(KEXON). The sky is the limit here. The following list is just a few ideas to get you started.
Scrapbook paper. Scrapbook paper is relatively inexpensive and widely available. Bottle caps are small, making them a great option for using up paper scraps from larger projects.
Colored cardstock. If you're going to be adding dimensional embellishments or layering multiple papers, you may want to start with a simple sheet of card stock.
Sheet music. Personally I've found that copying or printing sheet music on card stock AND coating it with spray acrylic keeps the paper and the ink from bleeding.
Photos. I also like to use photos that I've printed on card stock and coated. I use a Collage Sheet Software to format my photos in circles. You can opt for Photoshop or other photo editing programs, too.
Old book pages. Scraping old books or thrifting second hand books are both very popular techniques for crafting.
Just about any other type of recycled or re-purposed paper. Again, the sky is the limit. I recommend using a thicker paper so that it doesn't bleed, but you can attempt anything you like.
Fabric scraps. If you have fabric scraps instead of paper scraps, give those a go. Fabric glue or an all-purpose glue such as Tacky or Mod Podge may work better for the initial glue layer on your caps.
Buttons. Of course I had to include buttons here. Surprisingly enough, I have not actually tried this yet, but I need to do that now.
Self-adhesive rhinestones. You'll find these in most craft stores. The self-adhesive makes them easy to apply.
Glitter or glitter glue. Glitter glue is the less messy option here, particularly if you're making these crafts with kids.
Spray paint. This is a great option if you want to quickly decorate blank crafting caps or want a single color for all of your genuine caps.
Acrylic paint. Choose acrylic instead of spray paint for adding small details.
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