You could culture wild yeasts like this: In a sterilized jar mix equal portions RAW, unpasteurized honey (raw or unpasteurized honeys sometimes have the wild yeasts and enzymes in them) and spring water. Mix this well and cover the hjar with a paper kitchen towel. this will keep out bugs and dust. The payer towel is porous which will allow the air, which all around us contains 'wild yeast strains' When you see a few bubbles rising on the surface of this mixture, you're basically 'good to go'. Add a bit more honey to this mixture, stir well with a sterilized spoon, (you don't want to contaminate the starter) and let it go a few days longer. You want to make sure you've got a lively and strong fermentation going before adding this to your main batch of mead. One of the problems with wild yeasts; they're fickle, and you don't know if you've captured a good yeast strain or one that'll possibly spoil your mead. That's why it's best to use a cultured wine yeast, like 'Red Star' Pasteur Champagne. This cultured yeast is pure and has nothing bad that could spoil your batch of mead. With sourdough, the process is different. i live in San Francisco and acquired a heritage sourdough starter many years ago that bakes sourdough bread as good if not better than any commercial sourdough i've tasted and I've tasted many, having lived here for over 30 years. Recently i tried making a sourdough starter from scratch. I used water from boiled potatoes. I set the cooled potato water in a large sterilized jar, covered it with a paper towel held down with a rubber band for several days until it became cloudy and i waw bubbles around the surface of the potato water. then I added a bit of unbleached flour to give it some 'food' and let it go for a couple of days more. Since I had about 2 cups of potato water, I ended up adding 2 cups of unbleached flour in 1/2 cup increments every 12 hours or so until the mixture looks like pancake batter but was full of air bubbles so i knew I'd captured 'Lactobacillus'. Then i refrigerated it for a couple of days t let it rest. A few days later i took it out of refrigeration, poured off half of the batter, ( I made pancakes with this, why throw it away), added equal parts spring water and unbleached flour to the large jar, stirred it well with a sterilized spoon, covered it again with the paper towel and let sit on my kitchen counter overnight. By the next morning, it was foaming briskly. Then I knew I'd made a true sourdough starter. I store this in a large Italian 'Fido' canning jar or French 'Bocal' jar, the kind of jars with baling wire clamps, glass lids and rubber gaskets, just remove the gasket and replace it with a piece of saran wrap. Since a sourdough starter is alive and fermenting, closing it up tightly will result in an exploding jar and a mess in your refrigerator. When not using the starter, store it in the 'fridge' and when you want to bake bread double it up, pull half starter out to use and replace what you borrowed with equal parts pure spring water and unbleached flour, cover and set on the kitchen counter overnight to 'proof' return this to the 'fridge for your next batch. I use my heritage starter, which I understand from the guy i acquired it from, it has been in his family since the early 1900's as well as my home made starter in the same ways. Use approximately half the volume starter and half unbleached flour and if necessary some spring water if necessary to make a smooth dough. Knead this after mixing the starter and water and flour. until you have a smooth dough. Place it in a greased bowl and cover, set in a warm place to double, about two hours or so. Turn the dough out onto a floured source and knead briefly to form it into a loaf. Set in a warm place to double again, about 30-45 minutes. Slash the surface of the dough with a razor blade and sprinkle with cold water. Bake in a preheated 400 degree oven. for 45 minutes or until it looks golden brown