Remove all styles from a table?

[nurbles]

I'm converting an old site to use PICO CSS (so far it has been a great experience, thanks!) and I've hit a problem I cannot figure out: The site has a page that contains a large, complex table used to contain parts of an image -- essentially a table-based image map (I think that's the right term). Without PICO, the image formats perfectly, but with PICO different parts are scaled differently and things fit together quite poorly. I'd like to have this one table use no PICO styles, but I don't know how to do that. I've tried this in my little CSS file:

.clean_table table thead tbody tr th td img {
   all: initial;
}

and in the body, the table starts like this:

<div class="clean_table"><table

but this doesn't seem to have any affect on the table or images. I also tried using reset instead of initial, also with no effect. Oh, my first attempt was just the .clean_table, without any elements, to reset absolutely everything, but that did nothing either, at least not in Edge, where I'm testing right now. I suspect this should be simple, but I have been unable to stumble over the answer in my searching. Hopefully someone can (and will) help me out! Thanks!