5 May 2021
If you've looked at a cookbook from a fancy restaurant recently (or perhaps a recent recipe here on fivetwentysix), you may have noticed that ingredient quantities are specified in metric weights, with grams taking the place of familiar cups, tablespoons, teaspoons, and so on. Why are restaurants busting out the scales and adding 200 grams of sugar to their recipes instead of 1 cup of sugar? There is one incredibly simple reason for this: precision.
The reality is that a "cup of flour" might represent a totally different quantity of flour depending on the person measuring it, the measuring technique they use, or even the ambient humidity. However, 100 grams of flour is always 100 grams of flour, no matter what. Measuring ingredients by weight is simply the single most accurate and consistent way to cook. In top restaurants, consistency is key - dishes should be exactly the same for every guest, every night, and weight is the best way to communicate reproducible results. Accuracy and consistency is also important in the precise world of baking, and is non-optional when using modernist ingredients such as hydrocolloids, whch require incredibly small/precise quantities measured in tenths of a gram to function properly.
Dry, compressible ingredients such as flour and brown sugar are the most susceptible to error and variation when measuring by volume. The same is true for large particulate ingredients - how many cherries are in a cup of cherries, anyways? These errors and questions go away when specifying weights. Measuring by weight is only slightly less important for liquids, as a measured cup of liquid does not usually vary by a hugely significant amount. However, there is one more advantage to measuring all components by weight instead of volume: cleanup! When measuring by volume, you're usually left with an array of measuring cups and spoons that need cleaning. But when using weight, you can just set a bowl on a scale and add all your ingredients directly to the bowl, using the tare function to zero the displayed weight in between, leaving fewer things to clean afterwards.
At the end of the day, cooking is a flexible art. Having a dash more or less of one ingredient in your recipe might not affect the end result in a noticeable way, and some ingredients aren't measured in any way at all! If you do not bake or cook exacting modernist recipes often, you will probably continue to be just fine without a set of scales. A set of decent kitchen scales is relatively inexpensive though - I bought my scales with precisions of 1 gram and 0.01 gram for less than $30 combined. Consider picking some up - you may be pleasantly surprised at the results. If you do choose to buy a set of scales, you will need to find recipes written by weight, or convert your old recipes. For my old recipes that used US units, I just measured the ingredients by volume like I used to and weighed the results the first time - now I have the weights written down and can adjust them as I please.
Here are the scales I use for reference (these are not affiliate links):
In recipes specified in weights, you will often encounter instructions to add ingredients as a percentage by weight - given a pot of water, "add 20% sugar", for example. If you have 1000g water, how much sugar should you add? There are actually two ways to answer this question. The first is to add 20% of 1000g = 0.2 * 1000 = 200g of sugar. The other way is to add sugar such that it makes up 20% of the total weight of the final solution, in which case you would need to add 250g of sugar as 250g is 20% of a combined weight of 1250g. You'll notice that this is a difference of 50g, and that using the first method, the end result is actually only 16.67% sugar by weight (200g of sugar in 1200g of solution)! The Nordic Food Lab has noticed this disparity, and wrote an extensive article on the subject; they chose to call the first method "pluscent" when an ingredient is added as a percentage of another ingredient representing 100%, and call the second method a true percent out of 100.
All that being said - you will find the first method almost completely exlusively in cooking texts and discussions. This is the method that the Nordic Food Lab calls a "pluscent", although that word has not caught on in popular use. Despite the fact that it may lead to a unexpected percent concentation in the end result and may feel "wrong", measuring an ingredient as a percent of another 100% ingredient is easy to compute and is effectively the global standard. At the end of the day, it doesn't really matter if your solution is mathematically 20% sugar by total weight.
As an aside when adding ingredients in succesion: given instructions to "weigh and add 30% milk, 1% salt, and 0.1% xanthan gum", you don't need to continually re-weigh and measure percentages after adding each successive ingredient. Weigh the original product once, calculate the various quantities by percent, and add all at once.
Finally, this "pluscent" method is somewhat similar to baker's percentages also used by the folks at Modernist Cuisine, where the ingredient with the greatest effect on yield is labeled the 100% ingredient, and other ingredients are expressed as a percentage of the 100% ingredient's weight. For example, the Modernist Cuisine cheese sauce recipe calls for 100% grated cheese, 93% milk, and 4% sodium citrate. Don't be confused that these numbers don't seem to "add up" - remember that everything is relative to the 100% ingredient. This means that if you had 285g of grated cheese, that would be your 100% weight, and you would add 265g milk (93% of 285) and 11g sodium citrate (4% of 285). This method also lends itself to easy scaling up and down based on the quantity of the 100% ingredient that you have.
See The Math of Modern Cooking for instructions on calculating percentages and a handy-dandy calculator.
It can be a pain to measure out ingredients in advance when you're not exactly sure how much you'll end up using or if you're adding to taste. This is especially in the case with recipe development where you don't have a fully-specified recipe in advance. Cooking is an intuitive process and sometimes you want to just eyeball things but also end up with the weight of ingredients used to record for next time. This is possible by using the tare function in a clever way! Add your ingredients to the scale (say a bottle of soy sauce) and tare it to zero. Then, add as much as you'd like to your dish. When you place the bottle back on the scale it will show a negative weight representing the amount that you used!
Now that you've made it through all that - I hope you consider buying a set of cheap kitchen scales and measuring your ingredients by weight instead of volume. I think you'll find that your recipes are more consistent than ever before and that cleanup is a breeze!