A lot of people know that you should use a scale when baking. Baking is probably the only form of cooking that I can say is a science without people arguing with me. (Try saying "stir-fry is a science" or "candy-making is a science" without having the science vs. art discussion.) This is because just about every cookbook that covers baking discusses the importance of balancing acids and bases and precise measurements are of paramount importance when trying to transform a wet glob of batter into a glorious, fluffy dessert. To get precise measurements, we are told to toss out the measuring cups and use a kitchen scale. But is baking the only reason to use a scale?
The first and foremost reason is of course precision. Precision is how repeatable a measurement is. For example, if we measured a cup of all-purpose flour in a 1 cup (8 ounces) dry measuring cup, we expect the mass of the flour to be 125 grams. Assuming that the dry measuring cup is constructed to strict standards, the cup is accurate but not precise. Every time flour is measured, it is a bit more or a bit less than 125 g. How tightly packed the flour is, whether it has been recently sifted, if we scooped the flour or spooned it, all make an impact to the repeatability or precision of using a cup as a measuring device. On the other hand, a scale is precise (and accurate if calibrated). When a cup of flour is weighed on a scale, it is possible to add or take away flour until the scale registers 125 g. The precision of the scale is dependent on how easy it is to read the scale. In baking, using a scale to measure all the ingredients will ensure that you are following the recipe correctly (at least in terms of the proportions of ingredients). Using measuring cups could result in having a little more flour than leavening, etc.
Repeatability is a big reason why I use a scale. When I've figured out how much sugar to put into a recipe or how much butter is needed, using a scale means that next time I make the recipe it will have a greater chance of ending up exactly the same as I made it last time.
If precision and repeatability aren't motivating factors for getting a scale (and for most home chefs they don't sound too compelling), here's a good one: faster measuring. No more scooping with a measuring cup and then leveling the top with a straight edge. Simply pour into a bowl set on the scale and stop at the desired point. With fast response digital scales, the weight display is updated fast enough that you can pour until you hit the desired value. Then you can zero out the scale and measure your next ingredient in the same bowl. Less mess to clean up, faster measuring, and more precision. There are no drawbacks to using a kitchen scale (except perhaps the initial impact to your wallet).
Types of Scales
There are three main types of scales available for use in the kitchen. Balance, mechanical/spring, and digital. The three operate on different principals for measuring weight. The balance operates by performing comparisons between known masses and the object to be weighed. (Technically, a balance determines mass not weight and is the only type of scale that will work properly if you plan to cook on the moon. The balance in all other disciplines is considered separate from a scale, but in cooking we lump the two together.) The problem with the balance is that it only reports if the object you are measuring is greater or less than the known mass. For example, when using a balance to measure a cup of flour, 125 g of known mass is placed on one side of the balance while flour is placed on the other side until the mass on both sides are in balance. A beam balance has a beam with adjustable masses that move along the beam to increase torque applied to counteract the torque on the other end of the beam from the weight of the object being measured. (Exactly like the physician's scale at your doctor's office.) In general, a good balance is extremely accurate and can be extremely precise, but no matter how skilled the operator of the balance is, I feel it's a bit slow for use in the kitchen.
Mechanical scales use a platform mounted on a heavy spring to measure weight. An ideal spring compresses proportionally to the force applied to it. This means the weight placed on the platform is directly related to the distance that the platform moves down. The problem is that in actuality, springs aren't ideal. For the most part, they do exhibit the property of linear compression, but they also may change compression rates over time, may not return to their original length, and sometimes even break. Also, another problem with springs is that small quantities are harder to measure than large quantities. For example, if a scale is designed to measure up to 5 lbs. then then measuring one ounce of something will be more difficult than one pound. This is because the small amount of movement in the spring caused by one ounce will be difficult to detect because the scale is designed to move evenly throughout the whole five pounds. However, high quality mechanical scales can be quite precise, but they also carry a hefty price tag. Cheap mechanical scales can cost less than $10, but aren't terribly accurate or precise, but if these scales are the only ones you can afford, purchase a set of dry measuring cups instead. Properly used, the dry measuring cups will be more accurate and precise than the sub-$10 scales.
The final option is the digital scale. These scales range from $25 to over $100 with the vast majority in the $50 range. A good digital scale provides easy to read measurements with high precision. They work based on an electrical component called a strain gauge (also known as a load cell). The resistance of the strain gauge changes based upon the compression or change in shape of the component. A simple computer in the digital scale is preloaded at the factory with a table of values that allows it to calculate the weight of a load by the change in resistance. Many scales update about once a second, but better scales will update their readings much faster. This means, if you're pouring sugar into a bowl, the scale will provide almost instantaneous feedback so you don't pour too much. Most digital scales also have a tare function that allows the user to subtract the weight of the container from the measurement.
Features To Look For
A few months ago, WoodlandSprite directed me to Old Will Knott (retailer of fine scales) and the My Weigh i5000 Bowl Scale. I purchased the scale for $50 plus shipping and gave it a spin. This scale is well designed and is the perfect example of what features are important and how My Weigh managed to incorporate them. (Too bad I don't earn commission on the My Weigh i5000, because I'm about to explain why it's a great kitchen scale.)
Large Display - An easy to read display is important when measuring with a large mixing bowl on the platform. If the display is too small, it might be obscured by the bowl. Not only does the My Weigh i5000 have a large LCD display, a backlight turns on to illuminate the display so it's readable even if the shadow of the bowl is covering the display!
Avoirdupois (U.S.) and metric units - The ability to quickly and easily switch between U.S. (pounds and ounces) and metric (grams) units is useful when you have some recipes in grams and some in ounces. I receive some recipes that have both, so having a handy switch is a must. A few brands have their switches underneath the unit, so you can't switch while weighing. The i5000 has a nice button on the front that allows you to switch between grams, pounds and ounces (e.g. 1 lb. 8 oz.), pounds (e.g. 1.5 lb.), and counting mode (where the i5000 counts the number of jelly beans or whatever you put on the scale - which is, truthfully, the reason I bought the scale).
Tare - Taring is measuring the weight of the container. The tare function allows the scale to subtract the weight of the container and report only the net weight of the object being measured. Most scales allow you to repeatedly press the tare button, allowing you to measure many ingredients in the same bowl (e.g. measure flour, tare, measure sugar, tare, measure chocolate, tare, etc.). This is a wonderful feature and thankfully almost all digital scales have it. The i5000 also allows you to recall the gross weight (the actual weight) at anytime with a press of a button.
Seamless buttons - Some scales have buttons that are not, on the surface, formed from the same piece as the exterior of the scale. This means there are cracks where liquid or fine particles can get into and make cleaning a pain. Seamless buttons are a must especially if your fingers get dirty while working in the kitchen.
Removable bowl - Some scales have built-in bowls which makes cleaning more difficult and recipe preparation inconvenient. The ability to remove the bowl that comes with the scale (if it comes with one) and replacing it with your measuring cup, mixing bowl, or pot just makes everything that much easier. Although the i5000 came with a plastic bowl, I've never used it except to demonstrate to my friends the Jelly Belly counting trick.
Capacity - Most kitchen scales at the $50 price point measure up to 5 pounds (2.25 kg). This limits your ability to measure ingredients when using a glass mixing bowl or a pot which may weight a few pounds to begin with. The i5000 has an 11 pound (5 kg) capacity and manages to maintain a precision of 0.05 ounces (1 gram) throughout the range (most 5 kg scales have a 2 g granularity).
If you haven't guessed, my recommendation for a digital scale is the My Weigh i5000.
The My Weigh i5000 can be purchased for about $50 plus shipping from Old Will Knott. It's a bit more expensive elsewhere.