Before continuing with the topic, let it be known that the "experts" don't agree either. USDA requires graded retail eggs to be washed while the EU requires such eggs to be unwashed. So the USA and Europe are on opposite sides of the debate!
Info for those of you who don't have chickens....when an egg is being laid, the hen's "butt" slightly everts (turns out) keeping the egg clean. The egg's surface is wet but quickly dries due to the egg being hot. That surface moisture seals the eggshell with what is referred to as the "bloom". This bloom helps keep the egg's innards safe from outside contamination.
From what I can gather, if the egg does not get dirtied after being laid, then there is no reason to wash it. In fact, even in the USA some various state/local regulations require no egg washing for resale eggs. But other areas require all eggs to be washed, clean or not. How confusing!
In commercial mass egg production, eggs get filthy. Things are not like a typical homestead situation where the farmer hand gathers then cleans each egg individually. Thus US commercial eggs really need to go through a wash and a disinfecting rinse. In the past few years the industry takes things one step further by treating the shell with a sealant to keep moisture in and contaminants out. That sounds like a good thing but then again, how much of that chemical is leaching into the egg parts that we eat? If bacteria can get into a washed egg through the shell, so could the sealant chemicals. (Side note : people without refrigeration store eggs at room temperature in isinglass or coat the eggshell in vasoline. Sealing the shell works. Thus some homesteaders wipe their eggs with a rag moistened with food grade mineral oil in order to seal the shells of washed eggs.)
When the bloom is washed off, eggs are more susceptible to going bad quicker. "Bad bugs" can more readily enter a washed egg. While unwashed eggs can be stored on the kitchen counter for many days, washed eggs must be kept refrigerated.
So lets say that I have decided that I don't want to wash my eggs. What might I do? First off, I would use either sawdust or wood chips in the laying boxes. I've tried plenty of different substrates and have the best luck getting clean eggs using those two. Next I would maintain a deep litter in the chicken pen along with a roof to keep the litter protected from the rain. I just recently experimented with deep litter and found that the eggs are far, far cleaner. I'd also gather eggs frequently, 3-4 times a day if possible. The more frequently I check for eggs, the cleaner I find them. I'd use fine sandpaper to remove a speck of dirt, but any really soiled egg would need to be washed.
On the other side, what if I decide I prefer to wash my eggs? Well, using sawdust, deep litter, and frequent egg gathering are all still great ideas. But I'd follow some extra guidelines for washing. Generally recommendations that I've seen call for the temperature of the wash water should be 90 degrees F or 20 degrees F warmer than the egg's temperature. The idea is that the contents inside the egg would swell slightly, using internal pressure to keep contaminants from entering through the shell pores. Honestly, I'm not too sure that this is true. Perhaps just a wives tale or urban legend? But it sounds good, right?
For only slightly dirty eggs, I read that people clean them in a variety of ways. A light rubbing with fine grit sandpaper. A light wiping with a dampened cloth.
For dirtier eggs -- wiping with a wet cloth. Some people opt to wet the cloth with vinegar, peroxide, baking soda solution, or a mild bleach solution. Some people will use a soapy cloth or a dish scrubbing pad. Just about everyone then immediately rinses the egg in fresh running water, then either hand dries or sets them out on a towel to dry. There are commercial egg wash chemicals that can be purchased, too. Most websites say to not submerse eggs in the wash solution and don't soak them. But on the other hand, there are egg cleaning machines that do exactly that. So who is right, who is wrong, or is there no real difference?
On my homestead I opt for unwashed, clean eggs. I'll just lightly wipe clean eggs with a cloth barely dampened with a mild bleach solution and allow the egg to air dry before refrigerating. But sometimes, especially during rainy times, I do get dirty eggs no matter how much I try to keep nest boxes and substrates dry. And there are those days that I can only collect eggs morning and evening, and those eggs tend to be dirtier. So if I get some dirty eggs, I wash them with some dish detergent/water solution them immediately rinse them well in running water. Each egg gets set aside in a clean towel until all the dirtied eggs are washed. I then wipe each with a clean cloth dampened in a mild bleach solution and allow the eggs to air dry before refrigerating. The eggs are then stored in the coldest section of the refrigerator. And like many other homesteaders that I share info with, I also take the step to wipe the cleaned eggs with a mineral oil rag. Why? Because some of my buyers do not have refrigeration. The mineral oil seal helps keep their eggs fresher for the upcoming week.