I want to try my hand at making sourdough starter but live in high altitude and cold weather. I'm not sure if the altitude is an issue but I don't think my house is warm enough on its own to allow a starter to properly rise and ferment. Aside from I'm wondering if there are any other ways to create a warm, moist environment in which a starter could be successful.
You might want to try a desem starter. Have a look at the desem primer, which is also linked on the Wikipedia page. Starter instructions are given toward the end. Common lore says that desem starter should never get above 65F, which sounds perfect for your situation. (It's actually fine if it gets warmer than that, though.) Traditional conditions for creating a starter are 50-65F, and I imagine you must have an area at least in that temperature range. I don't think the high altitude should be an issue in getting a starter going, and it might actually help in the case of desem starter by allowing the internal sponge to grow slightly easier.
Basically, it's a dry dough sourdough starter -- different from the typical goupy or soupy sourdough starter most people work with. You begin a starter by essentially taking a little water and kneading in about as much whole grain flour as is reasonable to make a very dry little dough ball. (Whole wheat is traditional, but you can use other grains -- rye would probably be effective, but it's not traditional "desem.") Then bury it in flour. Standard practice is to throw half away every 24 hours and then add water and flour to repeat. You can also start with a very small amount and gradually enlarge the ball.
Eventually, you'll pull the ball out one day and it will be very soft and spongy inside. This will probably happen in about a week at low temperatures, but it could take more or less. At this point, I would usually do a few feedings 12 hours apart before using it to bake bread. If you want to ensure the strongest starter, I'd also do regular feedings for a few more days to really get the culture established.
You can easily convert a desem starter to a wetter version once it is established. Just add water to get the texture you want, and feed according to whatever starter recipe you want to follow.
And, of course, you can use to bake other kinds of bread. You can also convert it to another type of flour once established.
Why does this work better at lower temperatures? I've never actually tried it at very low temperatures (I've had success with a temp of 65F or so), but lots of people have. I think you might be able to get a more standard wet sourdough culture going with at least 50F temperatures -- I only recommend the desem method because anecdotally it's what a lot of people use at lower temperatures.
If it does work better, I assume it might have something to do with the way yeast and bacteria growth rates change at lower temperatures. Both are integral to a sourdough culture, but too much of one and not enough of the other, and the starter can fail. Early on in the creation of a starter, bacteria are much more active than yeast, and they produce a lot of byproducts, including acids which provide souring. In the first few days, you often end up with an excess of acetic acid (partly from bacteria that are undesirable and ultimately die off in the starter process), whereas a mature starter should produce more lactic acid. Excess acetic acid is known to be a significant inhibitor of yeast growth. So, at lower temperatures, the yeast may grow too slow and not have a chance to get established at all if there's too much acetic acid around. The high flour proportion in the desem starter could dilute the effect of all that acetic acid early on more effectively than in a wet starter. At least, that's what I'd theorize.
Regardless of the science, lots of people have success with the desem starter technique at lower temperatures. If you don't like maintaining that type of starter (which I personally have grown to like, because it seems to stay fresh longer with fewer feedings in the fridge once established), you can add more water once the starter is established.
As for allowing your dough to rise once you start baking, there are lots of ways to make a temporary humid warm space. If you have some small enclosed space that doesn't allow a lot of air circulation outside (microwave, small oven, etc.), put the dough in there along with a cup of hot water. Refresh the hot water as necessary to keep the desired temperature. If you don't have such a space, you can even take a large wider-than-tall cardboard box, cut off the top flaps, seal the bottom with packing tape, and invert it over your dough along with the cup of hot water. I used such makeshift proofing boxes for years until I actually was given a proofing box as a gift.
Frankly, you can let sourdough bread rise at lower temperatures, too, which will increase certain flavor elements. It will just take longer, and sometimes you might need to use a different amount of starter in the recipe so as not to end up with a loaf that's too sour in the end. But that will depend on the recipe and the specific characteristics of your mature starter.
Do you have a hot water heater? The room or the closet that houses it should be warm enough. That's where I grow my starter. (That's also where I bulk ferment and proof my loaves).
The altitude is not an issue. There are yeasts and bacteria on top of Mt. Everest.
Here's a schedule for you:
DAY 1 8:00 AM Sterilize container, add 190 g water @ 78 F (26 C), 94 g bread flour, stir, cover, store in warm place (I store it in my hot water heater closet).
DAY 2 DO NOTHING. DON'T SHAKE. DON'T STIR. DON'T UNCOVER. DON'T EVEN PEEK.
DAY 3 DO NOTHING
DAY 4 8:00 AM _ Add 47 g water @ 78 F (26 C), 25 g bread flour, stir, cover, store in warm place.
DAY 5 DO NOTHING
DAY 6 DO NOTHING
DAY 7 DO NOTHING
DAY 8 DO NOTHING
DAY 9 DO NOTHING
DAY 10 8:00 AM Pour off all but 100 g starter, add 47 g water @ 78 F (26 C), 31 g bread flour, stir, cover, store in a warm place.
DAY 10 2:00 PM Add 94 g water @ 78 F (26 C), 63 g bread flour, stir, cover, store in a warm place.
DAY 10 8:00 PM Add 190 g water @ 78 F (26 C), 125 g bread flour, stir, cover, store in a warm place.
DAY 11 8:00 AM Pour off all but 100 g starter, add 47 g water @ 78 F (26 C), 31 g bread flour, stir, cover, store in a warm place.
DAY 11 2:00 PM Add 94 g water @ 78 F (26 C), 63 g bread flour, stir, cover, store in a warm place.
DAY 11 8:00 PM Add 190 g water @ 78 F (26 C), 125 g bread flour, stir, cover, store in a warm place.
DAY 12 8:00 AM Pour off all but 100 g starter, add 47 g water @ 78 F (26 C), 31 g bread flour, stir, cover, store in a warm place.
DAY 12 2:00 PM Add 94 g water @ 78 F (26 C), 63 g bread flour, stir, cover, store in a warm place.
DAY 12 8:00 PM Add 190 g water @ 78 F (26 C), 125 g bread flour, stir, cover, store in a warm place.
DAY 13 8:00 AM Pour off all but 100 g starter, add 47 g water @ 78 F (26 C), 31 g bread flour, stir, cover, store in a warm place.
DAY 13 2:00 PM Add 94 g water @ 78 F (26 C), 63 g bread flour, stir, cover, store in a warm place.
DAY 13 8:00 PM Add 190 g water @ 78 F (26 C), 125 g bread flour, stir, cover, store in a warm place.
DAY 14 STARTER IS NOW STRONG ENOUGH TO BAKE
DAY 15+ CONTINUING STARTER MAINTAINENCE as equal parts starter, bread flour, water (1:1:1), but much smaller quantities of each 2x per day, such as 30 g starter, 30 g bread flour, 30 g water. If not baking for an extended period, put starter in the refrigerator to lie dormant until needed. To wake starter from dormancy, feed equal parts starter, bread flour, water (1:1:1) in whatever quantities needed 3x per day for 1-2 days, then adjust starter feeding/hydration to suit recipe.
Adding to some of the advice above:
There are only two critical times when you need a warm (as in above 65F) atmosphere for your starter: when you're first starting it, and during the 2nd rising of bread. At other times, sourdough is very tolerant of cold, it just slows down. I keep mine in the fridge so that I get 3 weeks between batches. It's 5 years old now and still going strong.
It seems that you could fairly easily use any number of techniques to keep the sourdough warm during startup and during 2nd rising for bread. One easy one is a damp or waterproof covering and a cliplight with a 100W incandesent light bulb (old-style, so it makes heat).
I know this question is rather old, but given the large amount of inaccurate or downright wrong information, I'll provide another answer anyway. I've been working with sourdough for years now and went through a lot of testing and analyzing the results to get where I am now. First off, some general facts about sourdough:
Sourdough consists of lactic acid bacteria and yeasts for the most part.
Depending on what kind of lactic acid bacteria you have in your dough, they can be pretty tolerant to heat. However, the yeasts are not, especially in regions with cooler climate. Starting at 40°C your yeasts in the sourdough will start to die. Generally, do not heat the sourdough above 35°C and do not use any ingredients any warmer than this. Also keep in mind that the sourdough can be 1-2°C warmer than the environment, due to microbial activity.
Lactic acid bacteria produces lactic acid (duh!) and a bit of acetic acid. How much of the latter depends, again, on your culture and the temperature (colder = more acetic acid, warmer = more lactic acid)
Yeasts like it warm. Around 25°C is a good temperature. Less than 15°C should be avoided if you want well developed yeasts.
If you have cool temperatures, you can alleviate the problem of having weak yeast and very sour dough a bit if you use more water than flour (about 1:1.5 flour/water instead if 1:1 like you normally would use).
Ok so here is how you make a starter from scratch:
Clean your bowl thoroughly!
Use natural flour, bleached or otherwise treated flour will increase the chance of failure a lot.
If you have chloride in your tap water, boil it before use (depending on where you live, this might be a good idea either way). Let it cool down below 40°C before you use it, tho.
You'll get the best results if you can keep temperatures somewhere around 25°C-30°C, but I've also succeeded in making a starter at about 15°C (I don't have experience with temperatures below this).
Note: Use 50% more water if you have temperatures around 15°C. I found this works best with type 1050 rye flour initially (refer to http://en.wikipedia.org/wiki/Flour#Flour_type_numbers for a rough conversion of my german type numbers), but you can start using pretty much any type of flour after that (I've tested rice, buckwheat, wheat, rye, spelt, barley, millet, oat and corn). Wholemeal can work fine, too. Just don't use the all-purpose flour (the completely white one), as this doesn't really contain all that much microbes anymore.
The process is rather simple: After you add 100g flour and water initially, you simply stir every 12 hours and add another 100g flour and water every 24 hours (every other time you stir the dough, you add flour and water). Do this for 4-5 days.
During these 5 days, the following can happen and is perfectly normal:
The dough can smell bad. The smell should go away after a day or two.
The dough may get light brown or white spots on top. This can happen after day 2-3 and is the yeast.
The dough may have bubbles at first and then go completely "silent" again. This is because several microbes are fighting to become dominant. Usually the lactic acid bacteria will win here (which is what we want) and "overwhelm" the other bacteria, making them stop producing gases. After the lactic acid bacteria settled, the wild yeasts will start to grow, forming a stable culture with the lactic acid bacteria.
If one of the following happens, the sourdough went bad and you have to start over (maybe try a different flour):
There are red, black, blue, green or "hairy" spots on the dough. This is mold. Don't try to rescue anything, it's spoiled and should be thrown away.
It smells very extremely like vinegar. It's okay to smell sour, but it normally won't smell so sour that it's repelling.
Now you should have a good bunch of sourdough, which you can use to bake.
A final note: I wouldn't let sourdough bread raise twice. You should only do it if you have strong yeast in your sourdough and even then it often doesn't work as well as you may hope, since apart from the yeast, the lactic acid bacteria is also "eating" the starch in the dough, quickly diminishing the food supply for the yeasts. I had my best results with only letting the dough raise once.
As long as your home is above 50F the bacteria and yeast in your starter will still be reasonably active- it will just take longer for them to work. When fermenting bread longer almost always means tastier.
That said- starting a starter from scratch already takes a long time so I understand your desire to speed it along a bit.
First of all- creating a moist environment is not going to be as important as the starter will be regularly recharged with flour and water- it won't get a chance to dry out.
As for temperature, my suggestions would be similar as for making yogurt-
- in a turned off (or very very low) oven
- covered and on a heating pad