A weird little thing happens in Photoshop when I make a spot channel. It changes the layer to “Multiply” when embedded Illustrator. I need it to be a normal layer (with overprint) for production.
Is there an option somewhere that I don’t know about regarding spot channels to get them to default to “normal” or is this just something that I have to check manually each time?
OR
Does anyone know how to write a script for that? (Not “record an action” or “batch processing”).
= Multiply
A Photoshop layer has no overprint setting. The Multiply blend mode is an equivalent.
Photoshop spot channels are meant to overprint onto the process channels within photoshop. When you have a spot channel in photoshop and no process pixel data (transparent background), it will inherently overprint when placed in other documents.
To fix this, you need to add a knockout layer in white on your process channels.
in the channels pallet, highlight the spot channel
Select all + copy
Highlight the process channels
in the layer pallet, create a new layer and fill with white
add a mask to that layer and highlight the mask only (not the layer)
select all + paste (you might need to invert the color on the mask, can’t remember off the top of my head)
I understand the theory. The thing is one of the printers we use for shrink wrapping requires the embedded file to be a 'normal" layer set to overprint fill. If it’s multiply it messes their RIP up.
That wasn’t my question but thank you. 
The question is: Is there a way to make the embedded image default to “normal” transparency mode instead of multiply. I understand why Adobe has this as the default. I need to know if I can manually change that default to “normal”.
The embedded image should already be set to ‘normal,’ by default within illustrator. its the spot channel layer from photoshop that makes it appear as ‘multiply’
Adding a white knockout layer in photoshop as I mentioned will prevent the PSD from appearing as ‘multiply/overprint’ when linked or embedded into other documents.
Don’t get me wrong. Your process is a fantastic creative solution. It’s exactly how I’d hope to receive a file from the artist. My goal is not how to prepare it though, but how to produce it. I’m only thinking production: quality, speed and error minimization in processing files for print.
If I can get the WHITE spot channel to default to normal automatically (without adding the extra steps) it’s worth my time because it eliminates one chance of human error.
This is an anomaly though because this is specific to only one press where RIP loses info if any layers are multiply AND set to overprint. It’s weird I know.