@Mitch Knight, I have a PDF from yesterday where the PANTONE color rendered (in the parent ai file) illustrator's overprint preview/separations preview as a process color, and in acrobat output preview the same way.

This morning, the same ai file saved again as PDF with the same joboptions renders the PANTONE color as a spot color as it should. The Illustrator separations preview panel in overprint preview mode is also showing it correctly.

I created a completely new file just to be certain and am seeing the correct behavior with all spot colors.
Not sure what the deal was yesterday, but that PDF I created doesn't lie... the PMS color does render as CMYK process in that one for whatever reason. Pretty strange

I am happy to confirm that this is fixed. Note: I see Lance's comment from September 01, 2020 12:49 but I cannot replicate his issue.

I was about ready to say this isn't fixed yet but it is fixed.... for *custom* spot colors only.

PANTONE spot colors are still converted to CMYK when a Gaussian blur is applied & PDF is created.

I can't think of a reason why that would be the intended behavior.

I am trying to print color separations for screenprinting using spot colors. I have have an object with a Gaussian blur effect that is a spot color but when I go to print it is being read as CMYK instead of spot so will not print correctly in my separations. I have used this method previously with no issues, not sure if it was something that was changed in the most recent update

24.2.3 update does NOT fix this issue despite a comment here that it does. I spoke with an Adobe support representative yesterday again and it was claimed that there is an internal build without set release date that has resolved this issue. The representative was very motivated to close the support ticket despite it not actually being resolved for the customer. I think that was because they are judged based on speed of ticket closure instead of outcome which is extremely dumb and unfortunate.

Hopefully we'll see another update soon.

Agreed, still an issue in 24.2.3, we've had to downgrade back to a previous version because of it.

When will the problem be solved?
It's a serious thing.

Sorry! The problem still exists. I did check it with drop shadow and it's ok, but with gaussian it's still broken :(

Not fixed on the 24.2.3, still the same problem.

PMS colors are still converted in CMYK when using a Photoshop effect in Illustrator.

I still have to work on an old version of Illustrator. Am I the only one?

It's fixed in the latest update (24.2.3)

When will the problem be resolved?
How should I explain to my customers that the artworks are not finished because the software is faulty?

That is not acceptable.

Prepress department of international producer of retail packaging. This is a very severe issue that should be immediately patched. It's already causing production issues for very large international brands.

This is a pathetic and inexcusable blunder. It just cost me an entire shift troubleshooting and then inventing a workaround. Absolutely ridiculous.

Luckily I stumbled upon this site. I thought I was losing it.

@ Anonymous:

There is a tedious work-around that involves photoshop:
Make your Gaussian blur object as usual in illustrator, expand appearance, then unembed the resultant image. Open it in photoshop, ctrl-click / command-click (whatever the mac equivalent is) to make a selection of the layer's transparency. Then go to channels and make a new spot channel in the pallet menu, fill with black. Select the desired spot color (PANTONE or whatever custom spot color you need), save the file with a new name and link that file back into illustrator in place of the one you unembedded.

You'll be able to select it and see that illustrator says it still uses the spot color.
Depending on what your output file is, for example PDF, you can use acrobat to view the output preview separations and verify that the blurred object is a spot color. See the images I have attached here.

Alternatively, you could use the same unembedded image from previous steps and change it to grayscale mode, then link *that* file back into your illustrator document and give it a fill with your desired spot color. I think that should also work though I haven't tested it.
EDIT: I tested the above method and it does work, but the CMYK-to-grayscale image is *too gray* to work as-is, you'll need to add a levels adjustment and drag the left-side (darkness/shadow) slider to the left-most edge of the histogram to darken it to black, and maybe drag the middle (midtones) slider a little right as well.

@ Adobe: not only is the illustrator blur rendered as CMYK by default, but it's DeviceCMYK at that... ignoring any color management policies. See the image I have attached here showing that the original blurred object is DeviceCMYK instead of GRACoL like it should've been.
EDIT: @Adobe, ignore the above. I was using a different PDF joboptions than normal which resulted in the CMYK being uncalibrated. CMYK's are calibrated as expected when the PDF is saved correctly.

I work in a screen printing shop and have used the gaussian blur in spot colors for years now. All of a sudden it is converting it back to CMYK colors. I see that others are having a similar problem, but don't see if progress has been made to fix this, as the original post is from the end of last month. I truly hope this will be resolved. This feature is something I use on a constant basis, and I don't see a very easy work around for it.

Yes its happing here too.

Please fix it asap. We cant check every artwork for this....

Can confirm this happens under Windows 10 also. I don't know that I ever used a photoshop raster effect on anything with a spot color before, though, so I don't have any previous work to compare my test file to.

Art saved to PDF, output preview in Acrobat does not list any spot color channels (art in illustrator is single vector rectangle with a spot color fill and stroke, then Gaussian blur applied)

When applying a guassian blur in Illustrator 24.2 on our Macs spot colors are changing to CMYK, even with the preserve spot colors option turned on.