How to Clear a Scratch Disk in Photoshop on an Old Mac

Not many things are more frustrating than receiving the “could not complete your request because the scratch disks are full” error while working on a project in Photoshop… Not only that, but the program will not let you continue until this issue is sorted out.

Unless you’ve come across this error before, you may be unaware of what a scratch disk is and how to clear your Photoshop cache. Fear not – this error is quite common in older Macs and there are some easy ways to fix it.

Why is my scratch disk full?

Like every other active application, Photoshop stores all temporary working files on your RAM (Random Access Memory). Once your RAM is full, however, Photoshop will start using one of your hard disks for extra memory space – these are also known as ‘scratch disks’. As you are creating and working on your projects, Photoshop simultaneously creates lots of temporary files which fill up your scratch disks too and, therefore, result in an error.



Clear your Photoshop cache

The easiest way to clear your scratch disk is by clearing your Photoshop cache. This will essentially get rid of all previous versions of your projects that are stored on your Mac as temporary files and will therefore empty more scratch disk space to work on new projects. Make sure all of your current projects are saved though, so you don’t lose any recent edits.

To do this, open up a project on Photoshop. From the menu bar, select Edit > Purge > All and click OK on the pop-up window. Repeat this step for other projects until the problem is solved.


Delete temporary files on Photoshop

Another easy fix for this error is to manually delete any temporary files on your Photoshop. To do this, simply get rid of any files with “.tmp” extension. You can also search “/tmp” on your Finder window, which will automatically find all temporary files and folders on your Mac, making them much easier to locate and delete.


Free up your disk space

While clearing your Photoshop cache or temporary files may get rid of the error, the roots of this issue lie in the cluttered hard disk on your Mac, and so it may not be long until you encounter it again. By freeing up as much space on your disk as possible you are more likely to get rid of this issue for good.

Clearing your hard disk means going through all of your files and deleting anything that you don’t need anymore. This may include getting rid of duplicate files, uninstalling and deleting unused applications (and any leftover files), clearing your browser caches, emptying your Recycle Bin, and so on.

While it is not necessary, it may be a good idea to always follow the 15% rule when it comes to your hard disk space. This rule suggests that you should have 15% of your memory space free at all times, allowing room for new files when working on projects on Photoshop or any other applications.