Anime-Beta TNG

There's a lot of smudge and dirt around most of my cels on the non-painted area, rarely do I have one that looks clean. How do I clean them up?

I would be hesitant to try anything with chemicals, so maybe try some distilled water? Do you have a picture? Vinegar syndrome can produce spots on cels, so hopefully that's not what you're looking at.
https://www.celoasis.com/index.php/home ... detection/
That site shows some pictures of what the crystal deposits look like, if it is that.

This is a multi-layer cel, it has so many.

Looks like it could be that symptom of VS maybe. Not sure if you can really remove it easily.

I doubt it. The layers aren't curved or distorted

I have cleaned cels that were simply dingy with mild dishwashing soap in water. Use a soft rag or tissue and go easily on painted or traced areas. Then pat dry with a clean cloth or tissue and hang from a clothes hanger until dry.

But from the photo these may be local areas of what I've heard called "oxidation." [I don't know what this is chemically, except that it is some kind of impurity and/or chemical action in the plastic itself.) Some batches of cellulose acetate are prone to developing these white spots in time, and as they are in the matrix of the cel sheet, they can't be removed. You might try rubbing a blank part with such spots with a soapy cloth to see..

I don't know that this is related to VS: in my experience that tends to start from painted areas, especially in multi-layer setups where a top painted area is stuck to a painted area on the bottom. It does suggest that the cel has previously been kept in a bad environment, and so tara's caution is valid to that degree: it's a cel that should be inspected more frequently in storage than others.