Deep Fat Fryer Boiling Over? Here’s Why & How To Prevent It

Despite the advent of air fryers and other cooking techniques that offer a healthier alternative to deep-frying, the taste of real fried food is deliciously unmistakable. However, many people opt not to deep fry at home because of the mess and cleanup involved, especially if you end up with a dreaded boil-over. Why does a deep fat fryer boil over and how can it be prevented?

A deep fat fryer boils over when foods have excessive moisture, are frozen, or have high starch content. Any oil that is too hot in an overfilled fryer can also cause a boil-over. To prevent it, try starting with half of the amount you normally would put in your fryer.

In this article, I’ll explain in detail the reasons that some foods cause a boil-over and some steps you can take to prevent it. Afterwards, I’ll discuss some other general maintenance tips for your deep-fat fryer. 

What Causes A Fryer To Boil Over?

Anyone who’s cooked with a deep fryer has experienced a slight moment of panic when the hot, bubbling oil quickly rises to the top. You hold your breath until the oil begins to calm down or it goes sloshing over the sides of the fryer. 

Boil over is usually caused by too much water on the food or putting frozen foods in too quickly. 

Starchy foods like potatoes can also cause a similar reaction. It’s important never to fill your fryer past the manufacturer’s “max” line or more than ⅔ of the way full to prevent overflow. 

Water and Oil Don’t Mix

The most common reason for your deep fat fryer to boil over is because there is too much water going into the hot oil. To better understand why this happens, we have to go back to your high school science class. 

Water boils at 212°F (100°C), which is well below the typical cooking temperatures for deep fat frying. When water boils, it turns into water vapor (steam), and when water droplets enter the heated cooking oil, it instantly moves from liquid to vapor and is forced upward to the oil’s surface. 

The more water droplets that end up in the oil, the more water vapor is trying to escape the oil, causing a bigger boil-over. The same holds true for frozen foods. If there are ice crystals on the outside, they will quickly be melted and turn to vapor. 

If there are no visible ice crystals on the outside, the quick heating of the food item will pull the moisture out, and the same process occurs. 

Starches and Hot Cooking Oil

Similar to water droplets, starches also undergo molecular changes when introduced to hot cooking oil. Starchy foods, like potatoes, are also high in moisture content. When fresh-cut fries are dropped into your fryer, the heat draws out the moisture, but something else happens to the starches themselves. 

When heated rapidly, starch molecules begin to expand and turn to gelatin. This process also helps to force additional moisture out of the food item and into the hot oil. 

In fact, a study published in  Food Research International looked at this process at the microscopic level to see the changes in action. 

How To Prevent Boil-Over in a Deep Fat Fryer

Now that we’ve discussed the science behind your fryer boiling over let’s talk about how you can prevent this dangerous mess from occurring in your kitchen. 

Here are some tips to make sure that your fryer doesn’t boil over: 

  • Dry off wet items. Whenever possible, make sure that you pat dry any excessively wet items before putting them into the fryer.
  • Soak your starches. Items that are high in starch, like potatoes, can be soaked for a while to help eliminate the risk of a boil-over. 
  • Drop with care. Always gently lower items into your deep fryer. Never drop them in from too far above the oil. Use tongs or your fingers and drop so that the splash is pointing away from you. 
  • Prevent splatters. The oil that pops and splatters can cause burns and other injuries. To prevent this, consider a fryer with a lid and vents.
  • Add frozen items slowly. Never dump a large number of frozen items into the fryer at once, but instead, add them one item or handful at a time. Wait for extra bubbles to go down before adding more. 
  • Don’t overfill oil. Follow the manufacturer’s guidelines for your fryer and never fill oil past the “max” line. When in doubt, only fill ⅔ the way full to leave room for oil to bubble and rise. 
  • Avoid overheating. Heat your fryer to the recipe’s specifications for the foods you’re making. There’s usually no need to crank it up to max temp and increase the chances of the oil boiling over. 
  • Fry in small batches. You don’t need to pour the whole bag of frozen french fries into the fryer in one batch. In fact, you should probably never do this unless you have a very large fryer. Use smaller batches for faster, more consistent cooking. 
  • Use breading. Roll wet items in bread crumbs, flour, or another dry breading to help absorb and lock in excess moisture and reduce the risk of boiling over. 
  • Freeze meltable items. If you’re feeling a little wild and decide to deep fry a candy bar or make fried ice cream, you’re going to want to make sure that it’s frozen solid before you batter and fry. Otherwise, you’re going to have a liquidy mess (and it will ruin the oil). 
  • Use a thermometer. To keep your oil temperature consistent as you add and remove items, use a thermometer specially designed for deep frying. 

Tools for Frying

When you’re cooking in your deep-fat fryer, you should always use the right tools to make sure that you don’t splatter hot oil or add items too quickly. Having the correct utensils will help prevent oil from boiling over when you’re adding food to the fryer.

It’s best to use tongs or a stainless steel strainer if you don’t have a fryer with a basket. 

There are some great options available on, like this Zulay mesh strainer. It has a long handle and is made of food-grade, rust-resistant stainless steel.

What To Do If Your Deep Fryer Boils Over

If your deep fat fryer does bubble up and over the sides, there are some things you should do to make sure that the cleanup efforts are safe and effective. Let’s take a closer look at these actions.

  1. Back away. As soon as it looks like your fryer is going to boil over, back away immediately. You won’t be able to stop it, so you want to make sure that you aren’t going to get burned by any splashing grease. 
  2. Unplug fryer. As soon as it is safe to do so, pull the plug out of the outlet to stop power from going to the unit. 
  3. Let it cool. Never try to clean up fryer grease while it is still hot. Always give it time to cool before attempting to handle oil. 
  4. Remove the food. Remove the food items from the grease when it’s safe to do so. You can decide whether you want to try cooking it again, but I recommend discarding this batch and starting fresh. 
  5. Wipe down surfaces. Use warm, soapy water or a degreaser to wipe down counters and the floor. Be mindful of any oil that is spilled so that you don’t slip in it. 

If Your Fryer Is on or Near a Stove…

If your fryer is near your stove, or even on it, you’ll need to take the following precautions to stop any fires that might have broken out:

  1. Cover the pot. If you have a lid or metal baking sheet handy, place it over the top of the fryer. 
  2. Turn off the power. As soon as you can, cut the power to the stove, using the breaker if needed. 
  3. NEVER use water. If the oil ignites, never use water to try to put it out. This will make the fire bigger and could cause an explosion. 
  4. Use salt or baking soda. If the fire is small, you can pour salt and baking soda on it to smother and extinguish the flames.
  5.  Use a fire extinguisher. As a final option, you can use a Class B chemical fire extinguisher.