i was thinking the painting thing too

NO, actually some of the old plastics and bakelite would actually releases gasses when stored in air tight containers. Others were damaged by sunlight...OLD white buttons that are not mother of pearl really do not hold up at all! you can paint them, but if there is already a chemical break down going on who knows what adding MORE chemicals might do to them!

You could always try soaking them in Polident (denture cleanser). Couldn't hurt...may help. It works to clean the insides of antique bottles that have been buried in old bottle dumps out in the woods.

Synthetic materials (especially early polymers) decompose over time. What the buttons were stored in, if they were exposed to heat and light, etc. make a huge difference. Unfortunately, trying to bleach them just compounds the problems.

If the buttons are something you are trying to use on something you are going to wash a lot, I wouldn't think painting would be the best option. It might work if you are using them for something decorative.

hey. I forgot, we use this to help remove yellowing from vintage linens as well! It does work!

New plastics off gas as well. Those gases can change the color of things, including some hand-dyed fabrics. That's why I don't use plastic to store my fabrics.

Try soaking them in denture cleaning tablets. Won't ruin them and just might work!

try putting them in a small dish with a bleach water solution and let them soak...then use a soft toothbrush to clean any residue in the holes or edges.

Depending on how many you have....and how old they are... you might look at eBay.... could be worth something to someone. Or just bottle them up in an old Mason jar, or a crystal glass of some type, and enjoy them on the shelf as a "Memory of Mother". (I would think that bleach may "melt them".)

How about trying that stuff that cleans dentures? Might work..