Fats That Build Seasoning

Which Cooking Fats Support Durable Seasoning, Which Ones Don't, and Why Lard Still Matters

There's a reason cast iron seasoning has inspired endless debate among collectors, restorers, and home cooks: the choice of fat matters more than most people realize. Not all fats polymerize equally, and the fat you choose determines whether your seasoning builds into a smooth, durable surface or flakes off after a few uses. After testing them all—vegetable oils, specialty oils, animal fats, and everything in between—I keep coming back to beef tallow as my top recommendation for building lasting seasoning on vintage cast iron.

The Science of Seasoning

Seasoning isn't just oil on iron—it's a chemical transformation. When fats are heated past their smoke point in the presence of iron (which acts as a catalyst), they undergo polymerization: the fat molecules break down, oxidize, and reform into long-chain polymers that bond with the iron surface and with each other. This creates the hard, hydrophobic coating that makes cast iron nonstick and rust-resistant.

The process has two components: polymerization (the fat converts to a hard, plastic-like layer) and carbonization (carbon residue from the fat integrates into the coating, contributing to color and durability). Both matter. A fat that polymerizes well but doesn't carbonize properly may look good but won't perform. A fat that carbonizes without proper polymerization leaves burnt residue instead of seasoning.

This is why understanding your fat's fatty acid profile and smoke point matters—it determines how the fat behaves during seasoning and what kind of coating results.

Fatty Acid Types and What They Mean

All cooking fats contain a mixture of three fatty acid types: saturated, monounsaturated, and polyunsaturated. The ratio determines seasoning behavior.

Polyunsaturated Fats

These fats contain multiple double bonds in their carbon chains, making them highly reactive. They polymerize most readily—sometimes too readily. Flaxseed oil (57% polyunsaturated) represents the extreme end: it polymerizes so quickly that it can form a brittle coating prone to flaking. Grapeseed oil and sunflower oil are also high in polyunsaturated fats and produce effective seasoning, though they require precise technique.

Monounsaturated Fats

These fats have one double bond, making them moderately reactive. They polymerize well but more slowly than polyunsaturated fats, often producing more durable results. Olive oil and avocado oil fall into this category. The polymerization isn't as aggressive, which can mean better adhesion and fewer flaking problems.

Saturated Fats

Saturated fats have no double bonds, making them chemically stable. Coconut oil (90% saturated) and butter are the most saturated common cooking fats. They don't polymerize as effectively, which is why coconut oil seasoning often remains soft or tacky rather than forming a hard coating. However, animal fats like lard and tallow, while containing significant saturated fat, also contain enough unsaturated fat to polymerize effectively—and their particular fatty acid profiles produce exceptionally durable seasoning.

My Top Recommendation: Beef Tallow

After testing every fat on this list—and I have tried them all—beef tallow consistently produces the most durable, best-performing seasoning on vintage cast iron. There's a reason restoration professionals have started returning to it.

The case for tallow: Beef tallow has a smoke point around 400°F, high enough for proper seasoning at standard oven temperatures. Its fatty acid profile—roughly 50% saturated, 42% monounsaturated, and 4% polyunsaturated—hits a sweet spot. The monounsaturated and polyunsaturated fats provide enough reactivity for good polymerization, while the saturated fat content contributes to stability. The result is a hard, dark patina that bonds firmly to the iron and doesn't flake.

Tallow seasoning withstands high-heat cooking, holds up to acidic foods better than many alternatives, and builds smoothly over time with regular use. It's what our grandparents used before industrial seed oils existed, and it works. Some restoration businesses now season exclusively with organic beef tallow, citing the natural stability of animal fats compared to processed vegetable oils.

Practical notes: Render your own tallow from beef suet for best results, or purchase food-grade tallow from a butcher or farm. Apply in very thin layers—the key to any successful seasoning. Season at 450-500°F for one hour per coat, allowing complete cooling between coats. Three to six coats establishes a solid base. If stored for long periods between uses, be aware that animal fats can go rancid; tallow keeps longest when refrigerated and used on pans in regular rotation.

Why Lard Still Matters

For centuries before Crisco arrived in 1911, American kitchens ran on lard. It seasoned cast iron, thickened gravies, made pie crusts flaky, and fried everything from chicken to donuts. Then came hydrogenated vegetable shortening, marketed as modern and clean, and lard fell out of fashion.

But lard remains one of the best seasoning fats available. Its smoke point (around 375°F) is adequate for seasoning, and its fatty acid profile—about 40% saturated, 45% monounsaturated, and 11% polyunsaturated—produces a smooth, resilient coating. The polyunsaturated content is enough for good polymerization without the brittleness problems of highly polyunsaturated oils like flaxseed.

A historical note: The lard our great-grandparents used was different from commercial lard today. Heritage pigs raised on pasture and natural forage produced fat higher in omega-3 fatty acids (the same polyunsaturated fats that make flaxseed oil a 'drying oil'). Modern pigs, raised on grain in confinement operations, produce lard lower in these reactive fats. If you can source lard from pasture-raised pigs, you'll get closer to what made grandma's skillets legendary.

Practical notes: Leaf lard—rendered from the fat around the kidneys—is the highest grade and produces the cleanest seasoning. Season at 400-425°F. Like tallow, lard can go rancid if stored too long, so use it on pans in regular rotation. Lodge Cast Iron still lists lard as a traditional option but notes that pans seasoned with animal fats and stored long-term may develop off odors.

Crisco and Vegetable Shortening

Crisco has been a cast iron seasoning standard for decades, and for good reason: it works. The high smoke point (around 490°F for modern formulations) allows seasoning at high temperatures without excessive smoking, and its refined nature means fewer impurities to burn and create off-odors. Many collectors and restorers swear by it.

The Cast Iron Collector website, a respected resource in the community, recommends Crisco for its reliability and availability. The seasoning it produces is durable and builds well with repeated use. For someone wanting a no-fuss, readily available option, solid vegetable shortening remains a solid choice.

Practical notes: Use the solid shortening (in the can), not liquid vegetable oil. Apply in extremely thin layers—most failed seasonings result from applying too much fat. Season at 400-450°F. Crisco doesn't go rancid as readily as animal fats, making it suitable for pans that may sit unused for extended periods.

Grapeseed Oil

Field Company pre-seasons their new skillets with grapeseed oil, and it's become a favorite among modern cast iron enthusiasts. The high polyunsaturated fat content (about 70%) makes it reactive enough for effective polymerization, while the high smoke point (around 420°F for refined versions) allows seasoning at appropriate temperatures.

Grapeseed oil produces a smooth, even seasoning that darkens nicely with use. It's neutral in flavor, readily available, and reasonably priced. For vegetable oil seasoning, it's one of the better options.

Practical notes: Use refined grapeseed oil, not cold-pressed (which has a lower smoke point). Season at 450°F. As with all polyunsaturated oils, watch for drips and pooling—thin, even coats are essential.

Flaxseed Oil: Proceed with Caution

Flaxseed oil generated enormous enthusiasm after food science blogger Sheryl Canter wrote about its theoretical superiority for seasoning in 2010. The logic was sound: flaxseed oil is a 'drying oil' (57% polyunsaturated fat, much of it omega-3 ALA), the same category as linseed oil used for oil paints and wood finishes. It should polymerize into an extremely hard surface.

In practice, results have been mixed. Many users report beautiful initial results followed by flaking—sometimes catastrophic flaking where the entire seasoning peels away. The very reactivity that makes flaxseed oil polymerize so readily may also make it brittle. Collector forums are full of warnings, with experienced members noting that flaxseed seasoning often looks perfect for display but fails under real cooking conditions.

Practical notes: If you want to try flaxseed oil, use only food-grade oil (refrigerated section, 100% flaxseed with no additives), apply in extremely thin layers, and season at the lowest effective temperature (some suggest 350°F, others go higher). Six or more coats may be needed. Be prepared for potential flaking. Some users have had success; many have been disappointed. I no longer recommend it for working skillets.

Canola and Vegetable Oils

Lodge recommends canola oil and vegetable oil for their availability and affordability, and both work adequately. Lodge's own seasoning spray is 100% canola oil. With smoke points around 400°F and decent unsaturation levels, these oils polymerize into functional seasoning.

That said, they're middle-of-the-road options. The seasoning they produce isn't as hard or as durable as tallow or shortening, and some users report tacky or uneven results. They're fine for maintenance coats and post-cleaning wipe-downs, but I wouldn't choose them for building a base seasoning on a restored piece.

Avocado Oil

Refined avocado oil has gained popularity for its very high smoke point (around 500-520°F) and neutral flavor. It's primarily monounsaturated fat (about 70%), which polymerizes effectively without the brittleness issues of highly polyunsaturated oils.

The main drawback is cost—avocado oil runs significantly more expensive than other options. If budget isn't a concern and you want a high-performing vegetable oil option, refined avocado oil produces good results.

Fats to Avoid for Seasoning

Coconut Oil

Despite its popularity for other uses, coconut oil is poorly suited for cast iron seasoning. Its 90% saturated fat content means it doesn't polymerize effectively—the coating tends to remain soft, tacky, or uneven rather than forming a hard, bonded surface. Save it for baking and body care.

Butter

Butter burns at low temperatures (250-300°F) before it can polymerize properly. The milk solids char while the fat hasn't bonded, leaving burnt residue rather than seasoning. Cook with butter in a well-seasoned pan, but don't use it to build that seasoning.

Extra Virgin Olive Oil

The low smoke point (325-375°F) and strong flavor make extra virgin olive oil a poor choice. It will smoke excessively at seasoning temperatures and can leave an off-taste. Light or refined olive oil (smoke point around 465°F) works better, but other options outperform it.

Bacon Grease

This one is controversial. Many home cooks swear by bacon grease, and it does contribute to seasoning during regular cooking. However, for intentional oven seasoning, bacon grease has problems: the salt content can create corrosion issues, the sugar in many bacons caramelizes and chars before the fat polymerizes, and the smoke and odor can be intense. Bacon grease is better for cooking on a well-seasoned surface than for building that surface from scratch.

Building Seasoning Through Use

Here's the truth every experienced cast iron user eventually learns: the best seasoning comes from cooking. Oven seasoning provides a foundation—a rust-protective base to start from—but the smooth, black, truly nonstick surface develops through years of regular use.

Every time you cook with fat in a cast iron pan, you're adding microscopic layers of seasoning. Frying bacon, searing steaks, making hash browns, cooking cornbread—each use deposits a bit more polymerized fat. This is why grandmother's skillet outperforms a newly seasoned restoration: it has decades of cooking layered into its surface.

The practical implication: don't obsess over achieving perfect seasoning before you start cooking. Get a functional base coat, then use the pan. Cook fatty foods at first—bacon, sausage, fried chicken—and let the seasoning build naturally. A pan that gets used daily will develop better seasoning than one that sits in the cupboard waiting for the 'perfect' moment.

Practical Summary

•         For best results: Beef tallow. It produces hard, durable seasoning that withstands high heat and regular use. Render your own or buy food-grade tallow.

•         Traditional alternative: Lard, preferably leaf lard from pasture-raised pigs. Proven over centuries.

•         Reliable modern option: Crisco solid shortening. High smoke point, consistent results, readily available.

•         Good vegetable oil choice: Refined grapeseed oil. High polyunsaturation for effective polymerization.

•         Premium option: Refined avocado oil. Very high smoke point, excellent polymerization, but expensive.

•         Use with caution: Flaxseed oil. Beautiful initial results for some, flaking problems for many.

•         Avoid for seasoning: Coconut oil, butter, extra virgin olive oil, and bacon grease (for oven seasoning).

•         Remember: Oven seasoning creates a foundation. Daily cooking builds the surface that makes cast iron legendary. Use your iron, and the seasoning will come.