h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The yolk of a hard boiled egg if stored for a time period in excess of 7 years will take on the appearance of a solid gold. Possibly not as valuable, but a definate conversation piece.

When your family didn't have a refrigerator and the eggs were what was available from half a dozen fowls usually in a feast or famine laying mood, storing eggs had more relevance than storing ancestors. The technique in the early 1950s in country-side New Zealand was to use a a product called Ovaline, yellow and greasy, that you rubbed over the egg surface to cover the pores that might admit air. The eggs were then wrapped in small pieces of newspaper and stacked in an apple box (which had open slatted sides) and stored in a dark, cool place. You got a few months out of this system.
To demonstrate the porosity of the shells, a neighbour who invented some excellent plastic moulding techinques had an early go at mass- cleaning eggs. He surmised that rolling dirty eggs againt one another in a concrete-mixer type contraption would do the trick. He produced beautifully white eggs that were packed with salmonella and chicken s**t and was lucky he didn't go to jail.
Saw on a Grenada cooking programme the other day a woman recommend that eggs be preserved by rubbing them with linseed oil. Wondered about this as I once used to be associated with the last linseed oil factory, probably, in the Southern Hemisphere. Desperate to show visiting directors that his factory had a future he served a morning tea with specially cooked linseed bikkies. In short time. all the diresctors got the s**ts. So eventually did the factory.