The Science of Soaking: Should You Soak Dishes Before Washing?

It’s a debate that happens in kitchens everywhere: should you let that casserole dish soak, or is it better to start scrubbing right away? You’ve likely heard different opinions, but the real answer lies in understanding what’s actually happening in your sink. This guide breaks down the science behind soaking to give you a clear answer.

How Soaking Actually Works

Before we decide when to soak, it helps to understand the science. Soaking works primarily through a process called rehydration. When food, especially starches and sugars, dries onto a plate or pan, it forms a hard, stubborn bond with the surface.

Adding water begins to reverse this process. Water molecules penetrate the dried food, causing it to swell and soften. This weakens its grip on the dish, making it significantly easier to scrub away. Hot water is particularly effective because the heat energy makes these molecules move faster, speeding up the entire process.

Furthermore, adding a drop of dish soap helps tremendously. Soaps contain surfactants, which are special molecules that reduce the surface tension of the water. This allows the water to spread out and penetrate the food grime more effectively, rather than just beading up on top of it.

When You Absolutely Should Soak Your Dishes

Soaking isn’t always the answer, but for certain types of messes, it’s a game-changer. It saves you time, effort, and the frustration of endless scrubbing.

For Baked-On Starches and Grains

This is the number one reason to soak. Think about the crusty remnants in a lasagna pan, the dried oatmeal cemented to the bottom of a pot, or the baked-on potato from a casserole dish. These foods are packed with starches that become rock-hard when they dry out.

Why it works: Soaking these items in hot, soapy water allows the starches to rehydrate and turn back into a softer, more gel-like consistency. After about 30 minutes, you’ll find that the residue wipes away with minimal effort.

For Burnt-On Sugars

If you’ve ever made caramel or had a sugary sauce burn onto the bottom of a saucepan, you know how difficult it can be to clean. Trying to chisel it off can damage your cookware.

Why it works: Sugar is highly soluble in water. Soaking the pan in hot water will dissolve the crystallized, burnt-on sugar, lifting it right off the surface. You often don’t even need to scrub; you can simply pour the dissolved sugar water out.

For Heavily Soiled Plates and Bowls

Sometimes life gets busy, and dishes from dinner sit out for a few hours or even overnight. Dried ketchup, hardened gravy, and other sauces can feel like they’re permanently attached.

Why it works: Just like with starches, a brief soak will rehydrate these dried-on messes. A 15 to 20-minute soak is usually all it takes to make washing these items as easy as if you had done them right after the meal.

When Soaking Is a Bad Idea

Soaking is not a universal solution. In some cases, it can be ineffective or even cause damage to your kitchenware. Here’s when you should skip the soak.

Greasy and Oily Pans

Soaking a greasy frying pan or an oily roasting tin in a sink full of water is counterproductive. Oil and water don’t mix, so the water won’t break down the grease. Instead, you’ll just end up with a greasy film floating on the water, which then coats the sink and every other dish you put in it.

What to do instead: First, scrape out any solid bits. Then, use a paper towel to wipe out as much excess grease as possible. Apply a high-quality degreasing dish soap, like Dawn Ultra, directly to the pan with a little hot water and scrub.

Cast Iron Cookware

This is the most important rule: never soak cast iron. Cast iron pans develop a non-stick layer called “seasoning,” which is formed by baked-on layers of oil. Soaking the pan, especially with soap, will strip this seasoning and expose the raw iron to water, leading to rust almost immediately.

What to do instead: While the pan is still warm, scrape out any food bits. Use a stiff brush or a chainmail scrubber with hot water to clean it. For very stuck-on food, you can use coarse salt as a gentle abrasive. Dry it thoroughly with a towel immediately, then place it on a warm burner for a minute to evaporate all moisture. Finally, wipe a very thin layer of cooking oil inside the pan to protect the seasoning.

Wooden Utensils and Cutting Boards

Wood is a porous material. When you soak wooden items, they absorb water, which can cause them to swell, warp, and crack over time. Worse, the moisture trapped inside can become a breeding ground for bacteria.

What to do instead: Wash wooden items by hand with hot, soapy water shortly after use. Rinse them and, most importantly, dry them immediately with a towel. Allow them to air dry completely before putting them away.

Sharp Knives

While a quick wash is fine, you should never leave sharp kitchen knives soaking in the sink. First, it’s a safety hazard. Reaching into a sink of murky water and forgetting a sharp knife is in there is a recipe for a bad cut. Second, soaking can damage the knife. It can dull the blade’s edge and, for knives with wooden or composite handles, cause the handle material to warp or loosen.

What to do instead: Carefully wash knives by hand one at a time. Hold the blade facing away from you and wash it from the spine to the edge. Dry it immediately and store it in a knife block or on a magnetic strip.

Frequently Asked Questions

How long should I soak dishes for? For most messes, 15 to 30 minutes is plenty. For extremely tough, baked-on food, you might go for an hour or two. Avoid soaking dishes overnight, as the standing water can become a breeding ground for bacteria and start to smell unpleasant.

Can I soak dishes in cold water? You can, but it’s much less effective. Hot water provides the energy needed to speed up the process of dissolving and rehydrating food particles. If you only have cold water, you will need to soak the items for a much longer period.

Does soaking dishes help save water? It can! If you have a very stubborn pot, letting it soak for 30 minutes is far more water-efficient than running the tap continuously for five minutes while you scrub relentlessly. By letting the water do the hard work for you, you reduce scrubbing time and the amount of running water needed.