Normally, you can only burn a CD-R disc one time. However, if you use Disk Utility to burn the disc, you can set it up for “multisession” burning so that you can burn more disk images on the disc in the future, assuming space is available on the disc.
1. In the Finder, create a folder for the session and drag the items you want to burn into the folder.
2. In Disk Utility, choose File > New > “Disk Image from Folder.” Then select the folder you created in the dialog and click Open.
3. Type a name for the image, choose a disk format, and click Save.
4. Mac OS Extended allows burning the disc more than once. Formats such as ISO allow burning the disc only once.
5. When the disk image is complete, select it in the Disk Utility list and choose Images > Burn or click Burn in the toolbar.
6. Insert a blank CD in the optical drive.
Select the “Leave disc appendable” checkbox. If you don’t see this option, click the triangle in the top-right corner.
7. Click Burn.
To add disk images to the disc later, follow the steps above to create a new disk image and burn it to the disc. You can continue this process until all available space on the disc is used.