Seasoning Cast Iron Grates: Creating a Natural Non-Stick Surface
A methodical process of applying and heat-bonding oil to cast iron grates to create a durable, non-stick cooking surface.
Method:
Seasoning cast iron grates is an essential technique that creates a natural, non-stick surface through a process called polymerisation. This process bonds oil molecules to the iron, creating a durable, protective layer that not only prevents food from sticking but also guards against rust and corrosion. Properly seasoned cast iron grates will develop a dark, smooth patina over time that enhances both cooking performance and food flavour.
Step 1:
Remove the cast iron grates from your grill and thoroughly clean them to remove any existing debris, food particles, or rust. For new grates, wash with warm soapy water to remove any manufacturing residue or protective coating. For used grates, use a grill brush or steel scrubber to remove built-up carbon and residue. This ensures the oil can bond directly with the iron surface.
Step 2:
Rinse the grates thoroughly with warm water and dry them completely using paper towels or a clean cloth. Any moisture left on the grates will interfere with the seasoning process and potentially cause rust spots. For thorough drying, place the clean grates in a warm oven at about 100°C (212°F) for 5-10 minutes.
Step 3:
Apply a thin, even coat of high-temperature oil to all surfaces of the grates, including the undersides and edges. Using a cloth or paper towel, wipe away excess oil until the grates appear almost dry. A common mistake is leaving too much oil, which will create a sticky, uneven finish rather than a smooth patina. The grates should look lightly oiled but not wet.
Step 4:
Heat your grill or oven to approximately 230-260°C (450-500°F). This high temperature is crucial for proper polymerisation of the oil. If using an oven, place the grates upside down on the middle rack with aluminium foil on the lower rack to catch any drips.
Step 5:
Bake or heat the oiled grates for 45-60 minutes. During this time, the oil will break down and bond with the iron, creating the non-stick surface. The grates will likely smoke during this process, which is normal and indicates that polymerisation is occurring. Ensure your space is well-ventilated.
Step 6:
Turn off the heat and allow the grates to cool completely in the oven or on the grill. This cooling period is crucial for the hardening of the polymerised oil layer. Removing the grates while still hot can damage the developing seasoning and potentially cause burns.
Step 7:
Repeat the oiling and heating process 2-3 more times to build up multiple thin layers of seasoning. Each layer strengthens the non-stick properties and rust resistance. While time-consuming, these additional layers create a significantly more durable cooking surface that will require less maintenance over time.
Step 8:
After the final cooling cycle, your cast iron grates are ready to use. The surface should be smooth, black, and slightly shiny. To maintain this seasoning, avoid harsh cleaners and scouring pads after cooking, as these will remove the seasoned layer you've worked to create.
Equipment Required:
- High-Temperature Cooking Oil:
Flaxseed oil (ideal), grapeseed oil, or vegetable shortening. Avoid olive oil as its smoke point is too low for proper polymerisation.
- Heat-Resistant Gloves:
Rated for high heat to safely handle hot grates during the process.
- Grill Brush or Stainless Steel Scrubber:
For cleaning the grates before seasoning. Wire brushes with loose bristles should be avoided for safety reasons.
- Clean, Lint-Free Cloths or Paper Towels:
For applying oil evenly without leaving residue.
- BBQ or Oven:
Capable of maintaining temperatures of 230-260°C (450-500°F) for at least an hour.
- Tongs or Hooks (Optional):
For handling hot grates if heat-resistant gloves are unavailable.
- Aluminium Foil (Optional):
To place under grates in oven to catch dripping oil.
Key Benefits:
- Extended Grate Lifespan:
Cast iron grates properly seasoned can last for decades rather than years, providing excellent value for your investment and maintaining consistent cooking performance over time.
- Natural Non-Stick Surface:
Well-seasoned cast iron creates a polymerised oil layer that prevents food from sticking without the need for chemical non-stick coatings, making your grilling experience more enjoyable with less food waste.
- Enhanced Flavour Transfer:
Properly seasoned grates develop a patina that contributes subtle flavour notes to grilled foods, particularly noticeable with delicate proteins like fish and chicken.
- Rust Prevention:
The seasoning process creates a protective barrier that shields cast iron from moisture and oxygen, effectively preventing rust formation when maintained properly.
- More Even Heat Distribution:
Seasoned cast iron grates distribute heat more effectively than unseasoned ones, reducing hot spots and creating more consistent cooking results across the entire grilling surface.
- Easier Cleaning and Maintenance:
Well-seasoned grates require significantly less scrubbing after use, saving you time and effort while extending the time between deep cleanings.
Tips and Tricks:
- Choose the Right Oil:
Flaxseed oil, though expensive, produces the hardest, most durable seasoning due to its high content of omega-3 fatty acids. Vegetable shortening and grapeseed oil are excellent alternatives with high smoke points. Avoid low smoke point oils like extra virgin olive oil or butter, which will burn rather than polymerise.
- Build Multiple Thin Layers:
Five thin layers of seasoning are far superior to one thick layer. Thin layers polymerise more completely and create a more durable finish. Be patient with the process rather than trying to rush it with thicker applications of oil.
- Maintain Between Uses:
After each grilling session, while the grates are still warm (not hot), apply a very light coat of oil using a cloth or paper towel. This "mini-seasoning" maintains and gradually improves the non-stick surface without requiring the full process again.
- Season New Grates Before First Use:
Even pre-seasoned cast iron grates benefit from additional seasoning before first use. Manufacturer's pre-seasoning is often minimal and primarily designed to prevent rust during shipping rather than provide optimal cooking performance.
- Heat Control During Seasoning:
Maintain a consistent temperature during the heating cycle. Fluctuations can cause uneven polymerisation. If your grill temperature is difficult to control, consider using an oven for the seasoning process instead.
- Seasonal Re-Seasoning:
Plan for a complete re-seasoning at the beginning and end of your grilling season. This twice-yearly maintenance significantly extends grate lifespan and maintains optimal performance.
Common Mistakes:
- Using Soap After Seasoning:
Regular dish soap contains degreasers that break down the polymerised oil layer. Clean seasoned grates with hot water and a grill brush or scraper instead. If soap is absolutely necessary, re-oil the grates lightly afterwards.
- Applying Too Much Oil:
Excess oil creates a sticky, uneven surface rather than a smooth patina. Grates should look almost dry after wiping—many beginners leave far too much oil on the surface. If your seasoned grates feel tacky, you've used too much oil and should start again.
- Insufficient Heating Time or Temperature:
Proper polymerisation requires both high heat (above 230°C/450°F) and sufficient time (45+ minutes). Lower temperatures or shorter durations result in a soft, impermanent coating that will wear off quickly and provide minimal protection.
- Soaking Cast Iron Grates:
Extended exposure to water breaks down seasoning and promotes rust. Never soak cast iron grates or leave them wet after cleaning. Always dry thoroughly and apply a light coat of oil if stored for more than a few days.
- Wire Brush Dangers:
Using wire brushes with loose bristles can leave metal fragments on your grates that may transfer to food. Always inspect grates after brushing and consider safer alternatives like nylon brushes, wooden scrapers, or crumpled aluminium foil.
Troubleshooting
- Rust Spots Appearing:
If rust spots develop, scour the affected area with steel wool until bare metal is visible, then immediately apply oil and re-season that section. Prevent future rust by ensuring grates are completely dry before storage and maintaining a light oil coating when not in use for extended periods.
- Food Still Sticking to Seasoned Grates:
This typically indicates incomplete seasoning. Ensure grates are adequately preheated before cooking (10-15 minutes) and properly oiled. If problems persist, perform another full seasoning cycle, being careful to apply thin, even coats and heat to proper temperature.
- Flaking or Peeling Seasoning:
Flaking occurs when oil layers are too thick or when drastic temperature changes stress the seasoning. Remove loose flakes with a scraper, clean the surface, and re-season with thinner oil applications. Avoid sudden temperature changes when possible.
- Gummy or Sticky Surface:
A sticky surface indicates that oil hasn't fully polymerised, usually from insufficient heat or time. Scrub away the sticky layer with hot water and a mild abrasive, dry completely, and repeat the seasoning process with proper temperature and duration.
- Uneven Colouring or Patchy Appearance:
Uneven seasoning often results from inconsistent oil application. For cosmetic issues with no functional impact, continue using the grates normally and the appearance will even out over time. For significant unevenness affecting cooking, strip and re-season the grates entirely.
Technique Adaptations
- Healthier Option: Avocado Oil Seasoning:
For health-conscious grillers, avocado oil offers a high smoke point (270°C/520°F) while containing beneficial monounsaturated fats. Though more expensive, it creates an excellent seasoning layer with potential health benefits compared to traditional vegetable shortening. Apply using the same technique but with slightly higher temperatures if possible.
- Flat Top Adaptation:
For cast iron flat tops or griddles, the seasoning process remains similar but requires more oil per application due to the larger surface area. Work in sections and use a bench scraper or spatula to ensure even distribution across the cooking surface.
- Apartment-Friendly Indoor Method:
For those without outdoor space, season indoors by increasing ventilation (open windows, use exhaust fans) and applying oil more sparingly to reduce smoke. Consider using high-smoke-point oils like refined safflower oil that produce less odour during polymerisation.
- Cold Weather Adaptation:
In temperatures below 5°C (40°F), warm the cast iron grates in an oven at 100°C (212°F) before applying oil to ensure proper absorption into the pores of the metal. Cold iron doesn't accept seasoning as effectively, resulting in uneven application and reduced durability.
