why does my psdc file seem to be taking up 20GB from macbook?

[Paola5EFD]

Why does my psdc file seem to be taking up so much space? How do i fix this?

I am working on a digital painting in Photoshop, which is stored in Creative Cloud. Before opening the file, I have 28GB of storage available on my Mac. As soon as I open up the Photoshop file I see my storage start to go down and then when i start to work on the file it  goes down even faster until my storage all the way to 8 GB. At this point the scratch disks are too full and I am no longer able to work on the file. When I purge the file, it doesn't really do much. When I close the document my storage goes back to 28GB and open the document back up the same thing happens again.  I will provide some information below about my MacBook and Photoshop file as well as a screenshot of the layers in my document.  

MacBook info:

Processor: 2.3 GHz Dual-Core Intel Core i5

Graphics: Intel Iris Plus Graphics 640 1536 MB

Memory: 8 GB 2133 MHz LPDDR3

Macbook storage available: 28 GB

PSD info:

Image size: 593.3 M

Image dimensions: 36  x 24 in

Resolution: 300ppi

[gener7]

That is not enough. You need at least 10x that much:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/scratch-disks-ram-hard-drive-full/td-...

How to set up external scratch disks if you can't free up hat much on your main drive.

https://helpx.adobe.com/photoshop/using/scratch-disks-preferences.html

Others (like D. Fosse) should be along to give you more details if you ask. He's light years ahead of me on scratch disks.

As a fun exercise, go to your Status Bar, select Scratch sizes and you can see how much all these layers are taking.

That about how much  my 300MB 37 layer PSD is taking up just by opening it and I don't know how Smart Objects affect it. Also 8 GB ram is pretty minimal. You want 16 and yes I know later macbooks won't allow you to change that.

You're going to need a bigger boat.

[Paola5EFD]

very helpful thank you! Here's the thing. I have a 1 terabyte external hard drive and I am so tempted to use it as my scratch disk. The thing is my external hard drive very often gets accidentally unplugged or comes loose from the port. Now let's say  I do use my external drive as my scratch disk, and it accidentally gets unplugged, could that cause all of my work to get deleted or corrupted? That's the only thing that's stopping me from using it really. i fear that happening.

[gener7]

I'd try a stronger and perhaps longer cable. And of course I think the drive has to be formatted HFS+ for Photoshop to recognize it. My magsafe power adaptor also easily comes loose, so I'd use some cello-tape to keep the USB connector in place for the duration of the project.
And keep extra copies of your valued files around.

Setup and use Time Machine for incremental copies that are even kept on your main drive.