Rescue Disk Problem created via Acronis TI 2015 build 6613

I purchased and installed Acronis True Image on 8/16/15. I am at build 6613. I created a Rescue Disk using a blank DVD-R. It appeared to go OK. When I tried booting it, it failed. It appeared unreadable. I tried using other DVD-R disks and had the same problem. I found using a CD-R worked OK. A friend of mine used a DVD+R that worked OK. What is the recommended disk type to use in creating a Rescue disk?