Many people have asked us how to “reuse” a regular blank CDR, so they can burn data to it multiple times. This is typically called session burning. You can purchase dedicated applications do this (such as Toast or Disco), but you can also use Disk Utility which is built into OS 10.4. It takes a little planning to make this work, but it can help you cut down on the number of CDs you have to burn (and buy).
This great tip comes from Apple:
First create a new folder and give it a descriptive name. Now put the files you want to burn into that folder. Go to your Applications folder and open the Utilities folder. Double-click on the Disk Utility application.
After it launches, in the menu bar at the top of the screen choose File > New > Disk Image from Folder. When the “Open” dialog box appears, find the folder you created earlier with the data you want to burn, and click “Image.” A “Save” dialog appears. You can leave the name as is or choose a new name (ignore the other options in this dialog box). Click Save. In a few moments, a disk image of your folder’s contents will appear in the list on the left side of the Disk Utility dialog. Click on that icon, and then click the burn button at the top left of the Disk Utility application.
When you click the Burn button, a dialog will appear asking to insert a disc. Do so, then click once the blue downward-facing triangle on the right side of this dialog to show more options. Click on the checkbox for “Leave disc appendable.” Now Click the “Burn” button.
Your data will now be written to that CD. To add more files later, just insert that same CD and use this same process all over again. Note that when you get to that final burn dialog, the button won’t say “Burn” this time, instead it will say “Append” because you’re adding these files to the same disc.
Don’t forget to remove the files you already burned to this disc from the folder you created above (and the DMG file it creates) before you make your next disc image.
Note that this is different than using a CDRW (compact disk re-writable). A CDRW can be erased and re-burned multiple times (however it’s not recommended to do this more than 10 times per disk). However, CDRWs don’t work in all drives, and are expensive. This is tip is designed for cheaper and more durable CDR’s.