Air bells, or something else?

I searched the forum and elsewhere to find a similar looking anomalie that I've been encountering on my negatives, but I'm just not certain what is going on.

I have experience developing, but recently have been encountering small spots with a halo around them. I give my tank good solid taps to dislodge bubbles, but could these be air bells? I don't typically presoak, and usually never have these spots.

I use a shared lab and the chemicals are mixed and maintained by a tech so I'd assume everything is right there, but you never know. I just want to figure out what I could be doing wrong in my workflow that could cause these annoying spots.

I give a final rinse in water with photoflo and hang in a drying cabinet. I've wondered if this could be a drying issue?

I'm attaching a crop that shows some of them. They don't occur on every frame. After turning positive, these appear as dark spots with a lighter halo around them. I appreciate your input and apologize if there was a similar post on this before that I missed. Thank you

D

I use a shared lab and the chemicals are mixed and maintained by a tech so I'd assume everything is right there

Does the tech filter the fixer between uses? If not take a funnel and coffee filter(s) with you when you go to the lab, put a filter in the funnel, pour the fixer through the filter/funnel into a graduate large enough to hold the volume of fixer needed for the processing then use the filtered fixer for fixing your film.

Residual silver will build up in fixer and redeposit itself onto film, filtering before each use reduces the chances of noticeable size particles redepositing on the film.

The fixer did have some particles in it, but I did not realize it could cause this effect.

No, I don't believe it can. As you said, they are dark spots on the positive, therefore they are clear spots on the negative. Fixer, or any residue in the fixer, simply does not cause already-developed parts of the film to become clear.

I can't be sure if they're air bells or not, but I would look to either that or some sort of contaminant getting on the film prior to developer.

No, I don't believe it can. As you said, they are dark spots on the positive, therefore they are clear spots on the negative. Fixer, or any residue in the fixer, simply does not cause already-developed parts of the film to become clear.

Fixer removes unexposed silver halides from film. Unexposed sliver halides are off white/cream colored. Once dissolved in fixer they remain off white/cream colored until the fixer has been left in light long enough to expose them. In a dark brown or amber jug it might take days to expose the dissolved silver halides. I use plastic bottles similar in color to milk jugs, filter the fixer before pouring back into the storage bottle and the bottle does not discolor. Upon pouring the used fixer into a milk jug and sitting outside for the water to evaporate off the jug turned dark grey/black after 8 to 12 hours of sunlight. I did not time it.

The pro lab I was using put me onto the redeposited silver halides in my negatives which were small white spots that could be seen under a loupe.

White/cream colored prints/scans as dark grey or black.

Test it for yourself.

Thirteenthumbs, the spots being shown appear black because the image has been inverted into a positive (derekcou says, "After turning positive, these appear as dark spots with a lighter halo around them.")

On the actual negative they are clear.

In order for fixer to cause such clear spots on a negative it would have to REMOVE some of the metallic silver that has already been developed. This just has nothing to do with anything that might be deposited on the negative later.

The spots do not appear black in the sample posted and derekcou does not state they are black, he does state they are dark. On my monitor the spots are a zone 3 gray.

You appear to be assuming blank spots on the film, I am not.

Filtering the fixer eliminated the problem in one instance. If continued filtering results in images free of similar defects then it is contaminates in the chemical.

Here's an example of definite air bells, FWIW. This is on a sheet of 4x5 and is just a part of the frame.