How Does a Slow Cooker Work

How Does a Slow Cooker Work: The Secret to Hands-Free, Scrumptious Meals

Last Updated on February 23, 2023

Inexpensive, easy to use, and a highly convenient way to healthier home-cooked meals, there are numerous reasons to invest in a slow cooker. But just how does a slow cooker work its magic, transforming cheap cuts into tasty, tender dishes? Let’s take a closer look and find out all there is to know about slow cookers, as well as how to use one.

What Is a Slow Cooker?

cooking appliance and bowl of rice on table

Slow cookers are small kitchen electrical appliances used to cook food on low heat over several hours. You may also hear them referred to as a “crock-pot”, after a popular slow cooker brand. They are a mains-operated, one-step cooking appliance that you can set-and-forget, making them an excellent choice for busy weekdays.

All slow cookers have three main parts—a heated base, a cooking pot, and a lid. Most will also have some kind of display and a timer. There’s often a temperature control with a high setting, low setting, and maybe a keep warm setting.

These kitchen appliances come in a range of sizes, from compact slow cookers with a two to three-person capacity up to seven litres for huge family meals.

Not only are slow cookers much loved for their simplicity and convenience, but they are also extremely popular for making deliciously tasty, hearty meals out of cheap cuts. So, you will save time, as well as also saving money on your food bills. If you use a slow cooker rather than your hob or oven for several hours, your energy bill will be reduced, as they are also highly energy efficient.

Thanks to their convenience, a slow cooker can be a great way to enable busy families to cook tasty food from scratch. Aside from saving money, it is also a great way to cook healthier meals and gives people complete control over exactly what goes into their food, unlike shop-bought ready meals.

How Does a Slow Cooker Work?

sales clerk and customer in appliance store

Slow cookers work by cooking your ingredients with a steady low heat over a longer cooking time than other cooking methods.

Once your appliance heats up and reaches the simmer point, it cooks your ingredients at that temperature for cooking times of several hours. The cooking process relies heavily upon the slow cooker’s lid being securely closed throughout the duration to minimise heat loss. This is why most models have a heavy glass lid or vacuum seal.

As your food heats up in the pot, slow cooking causes the moisture to rise. However, the moisture is unable to escape and condenses back down from the cover. As no moisture is lost and the heat is kept consistently low for a long time, your meal won’t dry out or need stirring. For this reason, even if left cooking at a low setting for 8 hours, it won’t catch on the bottom, unlike leaving a pot on your hob for hours on end. The heating element uses very little power, too, so it won’t ramp up your energy bills.

Not only does the locked-in moisture give you very soft and tender slow-cooked results, but it is also responsible for the incredible depth of flavour that you can get from using a slow cooker. Provided you don’t lift the lid, all of your food’s goodness remains inside your cooking pot for a maximum amount of taste.

Are Slow Cookers Easy to Use?

Making a home-cooked meal in a slow cooker is a simple process. Simply prepare your ingredients, place them in your slow cooker cooking pot in accordance with your recipe, replace the cover, and select your time and temperature options. Go about your daily business and come home to a piping hot, ready-to-eat meal.

Provided you follow the instructions provided by the manufacturer and use a slow cooker recipe, you can use the slow cooker for your meals while you’re working or out running errands. It really is that simple. However, if you are new to slow cooking or just want to know a little more about how to use your slow cooker for the best results, here are some of our favourite crock-pot usage tips.

  • The main difference between selecting high and low-temperature settings is that your food will reach a simmer point much earlier or later. So, if you are looking for a very tender casserole, for example, you’re going to benefit more from the low setting rather than leaving it simmering away for several hours longer on high.
  • Ensure that your recipe is adapted to your slow cooker capacity. Remember the golden rule of using a slow cooker: fill up to the halfway line as a minimum and two-thirds as a maximum. If you are making a large six portion recipe in your two-person slow cooker, obviously, you’ll need to adjust the quantities.
  • Searing meat and browning vegetables before adding them to your slow cooker are not essential but are still highly recommended for better colour, flavour, and texture.
  • As the heat comes from the bottom of your slow cooker, layer your ingredients in your cooking pot accordingly, with root type vegetables and tougher cuts of meat going in first.
  • Avoid using alcohol, as it can give a very bitter taste, as well as frozen ingredients which can take too long to heat up to safe temperatures in a slow cooker.

Slow cookers are by far one of the easiest kitchen appliances to use, having very basic settings. Prepping your ingredients beforehand can usually be done in just minutes, and your food needs no watching over or stirring as it transforms into a scrumptious meal.

What Can I Cook in a Slow Cooker?

Slow cookers are highly versatile. A quick search online will tell you that there’s an unbelievably long list of slow cooker uses. This nifty cooking tool can be used to cook much more than your standard stew consisting of meat and vegetables.

However, if you are new to using a slow cooker, make sure you start out by trying some specific slow cooker recipes. These are adapted to ensure that the ingredients, times and quantities are perfectly adapted for slow cookers.

Once you know how to use a slow cooker, you can try adapting your own recipes. Slow cookers are an excellent choice for a wide selection of meals, including curries, casseroles and joints of meat. Here are some of the most popular ingredients to use and what you should also avoid when whipping up slow cooker meals.

Popular Slow Cooker Ingredients

  • Inexpensive cuts of meat. Tougher pieces of meat tend to cost much less than “premium” tender cuts. However, these tougher cuts also have a lot of flavours when cooked correctly, and your slow cooker is the perfect way to do so. Slow cooking lamb shanks, pork shoulder, beef brisket, cheek or short rib are all popular choices.
  • Chicken thighs or any bone. Chicken joints are also suitable for use in your slow cooker recipes. Remember to remove any skin before cooking, or to finish off under your grill to crisp it up, or it will turn soggy and chewy.
  • Root vegetables. Root vegetables are ideal for cooking in your slow cooker, although you can also cook a wide variety of other vegetables. Tender vegetables (for example, mushrooms, green beans, courgettes and tomatoes) will benefit from being added towards the end of cooking your dish to ensure that they don’t become overcooked and mushy.
  • Beans and pulses. With the exception of kidney beans that must be boiled for ten minutes before slow cooking, you can use fresh or canned beans and pulses in your slow cooker. Chickpeas, lentils and cannellini beans are all popular options.

What Not to Cook in Your Slow Cooker

  • Alcohol. As we said earlier, avoid adding alcohol to your slow cooker recipes to avoid a bitter taste. As there is no evaporation as on your hob, you won’t get the same results.

Oven braise, never trust a slow cooker with alcohol marinade.

— BiasedGirl (@BiasedGirl) September 10, 2016

  • Dairy products. Dairy products don’t do well being heated for long periods of time. If you want to add cream, cheese or milk to your slow cooker recipe, do so just before the end. This can be done in the final thirty minutes, once you’re home and setting the table or preparing sides.
  • Fish. Fish is best cooked using other methods, although there are plenty of slow cooker fish recipes around, including fish stews. If you want to try one, be sure to use a firm type of fish and steer clear of delicate ones that will simply break up. You’ll probably want to add your fish to your other ingredients partway through cooking.
  • Pasta. Pasta is one of the things to avoid cooking on a slow cooker. Overcooked pasta forms a gunky, mushy mess. We recommended sticking to cooking your pasta on your hob to accompany your slow cooker meal. If you really wanted to, you could place it inside your slow cooker for the final 20 minutes, but it is unlikely to give you the best texture. Similarly, you’ll want to avoid cooking rice or couscous in your slow cooker.
  • Tender meats. Your expensive pork tenderloin and beef fillet steaks will be wasted in your slow cooker, ending up overcooked and chewy. Slow cookers are the best option for tenderising tougher, chewy cuts.

Do You Have to Put Water in a Slow Cooker?

Cooking a dish in the slow cooker

If your slow cooking recipe recommends adding water, then go ahead. Likewise, if you are cooking a stew, casserole or soup, you will want to add a small amount of cold water. However, remember that unlike cooking on your hob, water is retained in your slow cooker. If you are using a standard recipe, you may need to reduce the amount of liquid added by up to one third.

Another issue to consider is the level inside your slow cooker. Make sure you do not fill above the two-thirds mark. Even if you are making soup, you still won’t want to add any more, or you’ll risk your slow cooker creating a mess. It could also end up taking much longer to heat up fully, meaning your meal could be undercooked or even unsafe to eat.

So, make sure you reduce liquids when using your slow cooker. While some liquid is beneficial, remember a lot of your ingredients will create extra moisture. In general, depending on your specific recipe, you’ll probably want to just about cover your ingredients or slightly less.

If you have followed the recipe instructions and still need to reduce the amount of liquid in your slow cooker to thicken your sauce, then you can run it after the cooking period without its lid for another hour or so while you’re in the kitchen.

Is It Safe to Leave a Slow Cooker on All Day?

timer on electrical cooking appliance

Contrary to a lot of people’s worries, it is, in fact, safe to leave your slow cooker on all day, provided you respect your model’s safe usage practices. If you are planning on leaving your slow cooker on all day, or all night for that matter, here’s how to make sure your slow cooker is safe to leave on when you’re not home.

  1. First off, make sure that your recipe has a suitable cooking time for the duration of when you’re going to be either occupied or absent. You’ll need a low and slow recipe that lasts several hours long. So, if you are going out or working from home for the day, choose a slow cooking recipe with a duration of at least 8-12 hours.
  2. When you’re not going to be around, it is essential to verify that your slow cooker is between one half and two-thirds full of your ingredients. This is common practice, but even more important when you’re leaving your slow cooker on when you’re going to be out of the house. Overfill, and it could leak, underfill, and you’ll risk it running dry.
  3. Before you press start, check that your slow cooker is on a heatproof surface. Tiles are great, as are granite worktops. If you have a wooden or plastic-based kitchen worktop, you can use a cast iron trivet.
  4. Lastly, make sure that your slow cooker lid is correctly locked shut and that you place your unit at least 15cm away from your wall and any objects. If you have an overly long power cord, ensure that it does not come into contact with the sides of your slow cooker.


Slow cookers are definitely a must-have kitchen appliance. Easy to use, convenient, and affordable, they are an excellent way to “hands-free” slow cooking. No more standing over pots and pans required, you are free to get on with your busy life.

From joints of meat to curries, stews and casseroles, slow cookers are the best way to enjoy tasty home-made meals without the hassle now that you know exactly how does a slow cooker work.

Do you have slow cooking tips? Let us know in the comments.

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