Despite all the testing we have done to make our recipes foolproof, using a slow cooker isn’t an exact science; the issue is that heating power varies tremendously among brands of slow cookers. So as you are following our recipes, here are a few things you need to know.

In general, for our recipes we give either 1- or 2-hour ranges (and a wide array of cooking times) as guidelines for how long a recipe should be cooked. More delicate and exacting recipes using fish and leaner cuts of meat have the shorter time range (and shorter cooking times); we found this narrower range to be more reliable. We recommend that the first time you make one of these recipes you check for doneness at the lower end of the range.

While all ovens set to 350 degrees will perform the same (assuming all the ovens are properly calibrated—oven thermometers are the easiest way to monitor this), temperatures vary widely among slow cookers. We tested more than a dozen models and prepared every recipe in two different models. Some models run hot and fast, while others heat more slowly and gently. Most models perform best on low, but again it’s hard to make blanket statements that apply to all slow cookers. In our testing, we have found that some slow cookers run hot or cool on just one of the settings (either low or high). This is where the cook’s experience comes into play. If you have been using a slow cooker for some time, ask yourself if recipes are generally done at the low or high end of the cooking times provided in recipes. The answer should tell you whether you have a “fast” slow cooker or a “slow” model. If you are just getting started with your slow cooker, check all recipes at the beginning of the time range, but allow some extra time to cook food longer if necessary.

Slow cookers come in a variety of sizes, from the ridiculously small (1 quart) to the very big (7 quarts or more). In general, we like 6-quart models. That said, we tested our recipes in slow cookers of different sizes. Each recipe includes the size range that will work for that particular recipe, though the majority of the recipes work with 4- to 7-quart slow cookers. Note that some recipes must be made in a large slow cooker (at least 5 1/2 quarts) or you run the risk of overfilling the insert. The shape of the slow cooker also matters for some of our recipes: Oval slow cookers are needed to accommodate some roasts, casseroles, and braised vegetable dishes—they just won’t fit in a round slow cooker. If you don’t know the size of your slow cooker, check the underside of the insert (where the size is usually stamped), or simply measure how much water it takes to fill the insert to just above the lip.

Using a slow cooker is a safe way to cook food, but there are few things to keep in mind to ensure it is a safe process:

• First, make sure your slow cooker and your utensils have been properly cleaned.
• Do not let your meat or fish sit out on the counter for any length of time before adding them to the slow cooker.
• Never put frozen food into your slow cooker as this greatly increases the risk that your food will not reach a safe bacteria-killing temperature.

You should also follow our guidelines in recipes where we specify the doneness temperature of meat, fish, or poultry. It is advisable to keep the slow-cooker lid in place as this traps the heat and helps the slow cooker reach the ideal temperature zone.