What is This White Residue on My Grill Racks? Any of these 4 causes

by Joost Nusselder | Last Updated:  July 9, 2022

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If you’ve noticed a white residue on your grill, you may be wondering what it is and whether it’s safe to use your grill. Here’s what you need to know.

There’s some common advice many pitmasters like to share. Namely, that grilling is just as much of a science as it is an art form.

It’s advice that applies to grill maintenance, as well. Even novices know enough to let their meat cook to the right temperature and to let it sit for just the right amount of time. But when it comes to grill maintenance? They often overlook one of the biggest hazards: white residue.

What is This White Residue on My Grill?

The white residue on your grill could be ash or mold, but a white powdery substance most likely comes from the meat proteins that get released when juice leaves the meat. These proteins turn white when grilling on high heat.

White Residue on Your Grill: What is It and What Causes It?

Just imagine. You’ve wheeled out your barbecue grill earlier than usual because… well, your anticipation gets the best of you. Even in February. You rip off the cover only to discover a thick layer of ashy white fuzz even after you cleaned it thoroughly.

Or at least you thought you cleaned it thoroughly. But the reality is that the slightest hint of moisture and grease can turn a glistening steel grill rack into sludgy white residue overnight if you’re not careful.

But just what is that white residue? And when is it time to worry about it?

Meat proteins

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How to buy a bbq smoker video

The most obvious explanation is that the residue comes from the juices that get released from the meat when grilling.

These unavoidably get on your grill racks and the heat of the flames then turns the proteins in the juice into a white substance.

The heat also dries out the juices completely, resulting in a powdery residue on your grill racks.

It’s easy to spot if this is the problem when you look if it’s completely dry powder.

You should clean your racks before use if this is the case.

When is it Just Ash?

Ashes are an inevitable part of grilling, no matter if you’re using charcoal, wood or wood pellets. And on its own, ash may seem to be relatively harmless. There’s just one problem.

Once wood is burned, the ash contains various levels of potassium hydroxide and potassium carbonate (more commonly known as potash)—both of which are highly caustic agents which can cause severe burns to your skin if not disposed of properly.

But potash isn’t just caustic. It’s also highly water soluble, which leads many aspiring gardeners to use it as a fertilizer or compost. But what might be great for your garden is hardly going to be good for meat.

Especially when it leads to mold.

When is It Mold?

Much like anywhere else, mold is the direct result of moisture coming into contact with your grill or grill racks—especially after they haven’t been cleaned properly and stored under a grill cover or placed in a damp, unventilated area.

Grease residue acts like a magnet for mold, and failing to remove grease properly can turn your grill into a virtual farm for it. To make matters worse, mold isn’t always apparent from first glance. It can range from a green, brackish sludge to fuzzy, off-white spots lining your grill racks. It can smell musty or it can have practically no odor whatsoever. But there’s one common denominator when it comes to mold: it’s rarely harmless. 

Many forms of mold can contain mycotoxins which can lead to asthma, rashes, uncontrollable coughing, and for many immunocompromised people, severe lung infections requiring hospitalization. Luckily, you don’t necessarily need a hazmat suit in order to remove white residue (both harmful and non harmful) from your grill.

Soap residue

A last possibility is that some soap was left on the grill after cleaning it. You COULD get your nose close enough to smell if it soapy, but it’s probably best just to clean the grill again anyway :)

Elbow Grease, Not Grease—How to Remove White Residue and Mold From Your Grill

The first step to removing any caked on residue from your grill is to determine whether or not it’s a relatively harmless substance (such as ash or grease) or if it’s mold or another toxin. Make certain your grill and grill rack is thoroughly cooled down (trust me, you don’t want to skip this part!) and use a commercial grill and grate cleaner. Most come in different forms, ranging from instant foams and sprays to overnight cleaners, so make certain you follow the directions properly.

If after your grill or grill rack is fully dried you still notice stubborn residue along the grates or the insides, here are a few pointers to keep in mind:

Propane, Gas and Charcoal Grills

  1. If using a propane or gas grill, light it at the highest setting for at least 15 minutes to kill any potential mold or mold spores. If using a charcoal grill, discard any leftover charcoal or ash into a fire-safe container, and use new charcoal and fluid before igniting at high heat for the same amount of times.
  2. Once thoroughly cooled, remove the interior parts and place them on a safe, covered surface. Remove any rocks or briquettes and seal them in an airtight plastic bag before disposing of them.
  3. Spray the interior and grill parts with a commercial cleaner and allow to sit for at least 10 minutes before scrubbing them down with a scrub brush. Wipe clean, and rinse with a garden hose or spray. Repeat if necessary.
  4. Let dry and reassemble your grill, adding new briquettes, charcoal, or rocks. Heat the grill on a high heat for 10 – 15 minutes to help kill any lingering mold or spores.

Safety Pointers for Cleaning Your Grill

  • An effective everyday grill cleaner can be made from equal parts vinegar and water. If you’re using a gas grill, remove the grates before spraying, to avoid getting water in your burner. Use a wire grill brush to remove caked grease and debris.
  • After thoroughly drying, apply a light coal of olive oil to your grill gates with a clean rag to minimize debris and both your time and  effort in future cleanings.
  • At the bare minimum, always wear long pants, a long sleeve shirt, shoes, waterproof gloves and a dust mask when cleaning your grill of any potentially harmful residue such as mold and spores. Safety goggles can also protect your eyes from exposure to toxins.
Joost Nusselder, the founder of Lakeside Smokers is a content marketer, dad and loves trying out new food with BBQ Smoking (& Japanese food!) at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2016 to help loyal readers with recipes and cooking tips.