How Do I Measure "Stuff"?
Most beginning bakers are very, very concerned that they measure recipes correctly. They know that if they don't measure correctly, the bread won't come out right. More experienced artisan and home bakers are more likely to go by the feel of the dough, and an understanding of how the dough should feel to make the desired bread. Still, it takes a while to get to that point. And even for those experienced bakers, accurate measurements will help the experienced baker get close to the right dough more quickly than just dumping stuff into a mixing bowl and going on with it.
As a result, there are ongoing discussions about how to measure different things. At times, the discussions become quite irrational, and all too heated. In the interest of letting no good fight go by without getting in a swing or two, here's my spin on things.
Temperature - Let's look at the easy things first. Measuring temperatures. Use thermometers. A decent oven thermometer will set you back about $5.00 at your local grocery store. If you are concerned that a spring thermometer isn't very accurate, you're right. You can get a good mercury thermometer at a kitchen supply house for about $20.00. Of course, then you're putting mercury in your oven. Hope you don't break it. Overall, I think the less expensive spring thermometer is close enough. If you still want more accuracy, a number of companies are making BBQ thermometers that are designed to measure the inside of a BBQ pit. They work just fine for ovens also. Some are wireless so you can obsess over the temperature of your oven wherever you are. For baking, a single probe thermometer is adequate, and Thermopen seems to be the brand leader at this time.
If you let sourdough rise or ferment under controlled temperature, you'll want a second thermometer that is more accurate in the 70 to 100F range. I use a thermometer that is designed to fit in refrigerators, and it has a range from around -60 to 120F. It lets me know that my oven or proofer is really at 85F when it's time to proof dough or build a sourdough starter. Of course, you need to make sure that the thermometer is out of the oven when you start preheating the oven.
I have never been fond of the "thump test" to determine if bread is done. I'd rather use a thermometer to check its temperature. I use a chef's thermometer, the kind that has a longish metal probe and a dial to read the temperature. I turn over the loaf, and piece it from the bottom. That way I don't mar the top of the loaf. At 7,700 feet, I look for an internal temperature of around 195F. At sea level, I'd look for something closer to 205F.
Liquids - Measuring liquids is pretty easy too. Liquids may be accurately measured by volume or weight. Common US practice is to measure liquids by volume, that is, teaspoon, tablespoon, cup. Since liquids have a constant density, they can be measured either way.
The only real issue with measuring liquids is when you have to measure sticky liquids like sourdough starter, honey, or molasses. The answer is simple - measure any liquid oils you need to measure first. Then the other ingredients should fall out of your measuring cups easily. If you aren't using liquid oils, then use a spatula to pry out the last of the sticky liquids.
Solids - And now we get into touchy religious territory. Most of the world has moved to measuring by weight, in particular using the metric system, to measure solids both in the home and in the bakery. However, the United States largely sticks to volumetric measurement, at least in the home.
Some people insist that it is all but impossible to make good bread using volumetric measurement. That's patently absurd - people made good bread long before they used any real measurements, or even had fairly consistent flours.
My goal, as a cookbook and website author and as a baking instructor, is to teach people to make the breads that I am teaching them how to make. An experienced baker knows what dough should feel like, but communicating the correct feel in print is all but impossible. I find in the classes where we weigh there is a lot less variation between the breads different students make compared to the classes where we use cups. Using weight as a measuring tool helps the students get closer to where they need to be more easily than using cups, and that helps me be a better teacher. Why is that?
The big issue is that flour varies in density, depending on how you measure it. Most cookbooks and flour companies suggest you sift your flour, spoon the sifted flour into a cup, and then use a straight edge to scrape the excess from the top of the cup. Many bakers feel that life is too short for all that bother. Those people tend to just scoop the flour from the sack. There are other ways of filling cups. The problem is that flour is not a solid, but a granulated solid, so it can compact or settle.
If you transfer your flour to canisters to store your flour, I'm sure you've shaken your canister to get a bit more into it. There just wasn't enough in left in the sack to be worth storing the sack, but too much to throw away. So, you tap the canister, rap the sides, or something to get the flour to settle. I've been known to use a rubber mallet on plastic canisters. Guess what - a cup of the flour before you caused it to settle weighed less than after. Sacks of flour also settle as they age.
How significant is that? In a UseNet baking newsgroup a good number of people with scales measured the weight of a cup of flour the way they usually fill a cup. And a cup of flour ranged from less than 100 to more than 200 grams. Worse, the cup to cup variation was as much as 25% for the scoopers. The sifters were within 10 to 12% from cup to cup, which is better but not all that thrilling. Emily Buehler in her book, "Bread Science" suggests that weighing is a better predictor of how many molecules have been added to the mixing bowl than volumetric measurements.
Some people comment that flour isn't all that consistent. Flour, they say, will pick up water from the air on wet days and dry out on dry days. To some extent this is true. However industry studies show that the triple layer paper bags used by flour companies are quite good at maintaining the moisture levels in the flour, and the variation from day to day is best measured in single digit percentages. Honestly, if you are using cups, I doubt you'll notice the difference from batch to batch based on the moisture levels in the flour - you have enough other issues that will mask the small differences in flour from day to day.
Other people point out that flour varies from batch to batch, from brand to brand, and from season to season. Millers try very hard to minimize these differences. Sadly, the larger mills seem better able to dampen out the variations in this natural product. Still, weighing your ingredients will help you identify the differences and accommodate them more easily than measuring by cups.
A last word about the little ingredients in bread, salt and yeast (if you use yeast, of course). A common problem for bakers using digital scales is measuring salt and yeast. My cheapo scales only register within 2 grams. So, when I'm asked to measure 3 grams of salt, what is that? Common salt is pretty consistent, so it's easy to reliably measure it by volume. I sat down one day with a decent lab scale and measured teaspoons and grams of salt. Here's a handy-dandy conversion chart for salt.
1 TBSP = 15.75 gr
1 tsp = 5.25 gr
3/4 tsp = 3.9 gr
1/2 tsp = 2.6 gr
1/4 tsp = 1.3 gr
1/8 tsp = .65 gr
Then I repeated the process with yeast. Instant dry yeast, to be exact. Once again, here's a handy dandy conversion chart for instant dry yeast:
1 TBSP = 9.5 gr
1 tsp = 3.16 gr
3/4 tsp = 2.48 gr
1/2 tsp = 1.8 gr
1/4 tsp = 0.9 gr
1/8 tsp = .45 gr