Richard Smith, assistant professor at the University of Washington and expert in prints conservation, offers this recipe for preserving posters for generations.
- Dissolve one milk of magnesia tablet or teaspoon in a quart of bottled club soda, mix well, and let the stuff chill for eight hours or so in the refrigerator.
- Next, pour into a shallow pan and soak the poster in it for about an hour.
- Remove the poster and pat it dry as well as you can before allowing to dry more fully.
The effect of this soaking, says Smith, is to counteact the processes which eat away at the cellulose fibers of the paper, causing it to turn yellow and brittle with age. Having timeproofed them with this process you'll be able to keep your posters intact for as long as 300 years. However, you must remember to have the posters resoaked every fifty years.