Black spots on reversal-processed negatives

Hello everyone, I just started my way into alternative processes. Yesterday, I wanted to make some large internegatives for contact printing in cyanotype process.
So I used the Wephota FO5, a lith film, and did the reversal process... first, I determined the exposure time for normal paper, then I exposed the lith film the same time, but 2½ stops stopped down. Then I did a second exposure, without the negative, but from the same enlarger, for about one third of the first exposure time in order to reduce contrast in the end. Then developer (ADOX MCC 1+6, 5 minutes so as to get everything really developed...), stop bath (citric acid)...lights on! After washing under water (the positive looked a bit dark, but overall quite good at this stage) I put it in the reversal bleach. When all the metallic cilver seemed to have disappeared, I let it in for further 30 seconds, then washing for about 10 minutes, and again in the developer.
While the overall look of the negs is good (moderate contrast, good exposure), there are some black spots all over the negs. They are too big for dust particles, as they are about 3-5mm in diameter. Also, I have been doing test prints on paper and they had no sign of dust on them! So it seems that something in the reversal process seems to have created these spots... or can it have something to do with the film?
This is a photo of the negative:

(The photo of the negative is just that, a photo, not a scan, thus the reflection....it is not really there. But the black spots can well be seen)
Just for comparison, a print from the same settings just before:

Any ideas are appreciated!

Air bubbles in the first development, perhaps?

I used the Wephota FO5 film for the same purpose in the past and got resutls like yours. It only happened on film that I had purchased a few years before, so I'm not sure if the problem was age or storage related. Since then I have been using Arista Ortho Litho film with much more success.

You could send your scans to Wolfgang Moersch and ask if he has seen this problem before. He has used this film in the past.

I agree, those look like spots where the first development failed -- that left undeveloped halide, rather than developed silver, producing near D-max spots where the reversal turned what would have been clear spots in a fixed film positive black. The size, the fuzziness, both suggest the possibility of air bubbles.

Otherwise, if they were due to dust, it wasn't on the negative or the copy film, it was somewhere that would cast out of focus shadows, such as a contrast filter (which you wouldn't use to print on lith film) or similar -- in the light path, but out of the focal planes.

Donald Qualls said:

I agree, those look like spots where the first development failed -- that left undeveloped halide, rather than developed silver, producing near D-max spots where the reversal turned what would have been clear spots in a fixed film positive black. The size, the fuzziness, both suggest the possibility of air bubbles.

Otherwise, if they were due to dust, it wasn't on the negative or the copy film, it was somewhere that would cast out of focus shadows, such as a contrast filter (which you wouldn't use to print on lith film) or similar -- in the light path, but out of the focal planes.

Click to expand...

Thank You! I think it was something in the first developer, as I tried it again today with new developer, and got no problems....so maybe the developer was too weak...

يبدو فيلم (Arista Ortho Litho) جيدًا جدًا ، لم أتوقع أن يكون من فئة (Ortho).