canvas collage

[missh.livejournal.com]

I didn't see anything about this in the memories, so I apologize if this is a repeat.

I'm trying to make a collage of these club flyers I collected while I studied abroad last year. they're mostly glossy cardstock, about postcard size, and I want to use a canvas as my base.

unfortunately, I'm having trouble getting them to stick. I tried mod podge on one canvas, and it definitely wasn't strong enough, so I switched to some sort of polyurethane stuff I got in the hardware section of Wal-Mart, next to the wood stain. it works okay, but it leaves these weird bubbles, and it takes a lot to get them to stick. does anyone have any other suggestions?

thanks!