How to clean dirt from a poster

[pratschm]

I know there is another thread with a similar name, but that one focused mainly on box art.
That thread mentioned alcohol (rubbing alcohol?) and there was another thread that talked about lighter fluid (to remove tape).
Would using either of these with some cotton, or even letting it soak through and then lightly rubbing, be a good way to loosen dirt and similar?
The areas are both white, don't know if that makes a difference (is the alcohol/lighter fluid safe on the colored areas, ie, doesn't run the ink?)

Some spots on the corners. I don't want to say mold spots, but it kind of looks like mold spots. These are _ever so slightly_ raised.


This spot is different. It is raised, something that got stuck on there (don't know what). I was able to scrape a little off with a sharp edge, but didn't keep going so as to avoid starting to wear the paper. I thought soaking it might loosen it, but obviously wanted to ask first.

[CSM]

The top pic looks like foxing which would need bleaching/chemicals to get out (if it can be). 

The second looks like dried peanut butter If it's food, there's probably a grease stain underneath but maybe not.  Try and scrape it off very carefully

I wouldn't soak it in water unless you're going to linenback it.

[pratschm]

I've seen foxing mentioned before, but I didn't know what it was. Thought it was wrinkling of the paper of something. There is a bit more of that in 2 other corners. I'll give it a Google, but is there a 2-sec description of what foxing is? Natural discoloration of the paper due to <insert some chemical here>?

I don't think it's peanut butter. I was able to scrape a little of it off to where little pieces broke away. I didn't see any sort of grease stain underneath, so that's good. I didn't want to scrape anymore, though, because I didn't want to start scraping at paper.

I definitely wasn't going to use water. I just didn't know if the alcohol / lighter fluid mentioned in the other threads would work or have similar effects as using water(?) The impression I got was that using lighter fluid (at least in the case of tape) would evaporate away and not warp the paper. Is that incorrect?

---

And now that I've read about foxing, should I keep that paper away from the others???

[pratschm]

And now that I've read about foxing, should I keep that paper away from the others???

This was a serious question. Since foxing can be caused by fungus, can that spread to other paper if, for example, they are all lying flat on top each other?
I'm guessing if it's the metal oxide type, that would be less worrisome(?).

[CSM]

It can spread and if you have some posters with bad foxing best idea is to have them separated by poly bags or acid-free sheets

[pratschm]

Ok, thank you. I did separate that one from the bunch just to be safe.
I read somewhere that applying hydrogen peroxide in small amounts over and over can help clear it up, though that might have been for books / heavier paper. Anyone know if that works for this type of paper? I'd be worried that it would cause the paper to start wrinkling in that 'water damaged' sort of way.
Also, if I were to get the paper bleached professionally, would that mean it would have to be linenbacked? Or is that something that can be done without requiring lb'ing?
Thanks for the help.