Will seasoning a cast iron skillet with vegetable oil leave trans fats?

No. When vegetable oil is used to season cast iron, the oil bonds to the iron and forms a hard, slick layer, and the makers of the skillets compared here do not publish a trans fat figure for that seasoning. What the seasoning layer is made of, and what the makers say about it, is set out below.

What the seasoning layer actually is

Seasoning is oil that has been heated past its smoke point on the surface of the iron. The fatty acids link to each other and to the metal, forming a polymer film that fills the pores of the cast surface. That film is plastic-like and bonded, not a pool of liquid oil sitting in the pan. A bonded polymer is a different material from the oil in the bottle.

The makers describe this layer in their own words. Lodge states that it seasons its cookware with 100% vegetable oil and that there are no synthetic coatings or chemicals, and it calls the result a natural, easy-release finish that improves with use. EDGING CASTING states that its 17 inch skillet is pre-seasoned with vegetable oil, again with no synthetic coatings or chemicals. Neither statement mentions trans fat.

Victoria takes a different route and states that it seasons its pan with non-GMO, kosher-certified flaxseed oil, and that the pan is PTFE- and PFOA-free. Backcountry Iron states that its skillet is pre-seasoned with a proprietary oil blend. Cuisinel states only that its skillet is pre-seasoned, without naming the oil.

Why the trans fat question comes up at all

Partially hydrogenated oils were once the standard source of trans fat in food, and they were used in some commercial seasoning processes decades ago. That history is why the question gets asked. The skillets compared in Best Cast Iron Skillets for Five Different Kitchens are current products, and the makers describe their seasoning as vegetable oil, flaxseed oil or a proprietary blend.

None of the five makers publishes a trans fat content for its seasoning layer. That absence is worth stating plainly: this site has not compared trans fat figures for these skillets, because the makers do not publish them. What the makers do publish is the oil used and, in two cases, the absence of synthetic coatings and chemicals.

The practical point is that a polymerized film is not eaten in any meaningful quantity. The seasoning stays on the pan. Food cooked in a seasoned skillet contacts a hard, bonded surface, not a layer of free oil.

What each maker publishes about its seasoning

Lodge is the most explicit of the five. Its 10.25 inch skillet, listed at 5.35 pounds and 10.68 inches wide, is seasoned with 100% vegetable oil, and Lodge states there are no synthetic coatings or chemicals. Lodge also gives care instructions: hand wash, dry, rub with cooking oil. Nothing in that text addresses trans fat.

EDGING CASTING’s 17 inch skillet, listed at 14.75 pounds and 17 inches wide, is pre-seasoned with vegetable oil under the same no synthetic coatings or chemicals language. Victoria’s 10 inch skillet, listed at 4.8 pounds and 11 inches wide, names flaxseed oil and states the pan is PTFE- and PFOA-free. Backcountry Iron’s 12 inch skillet, listed at 7.0 pounds and 12.8 inches wide, names a proprietary oil blend. Cuisinel’s 12 inch skillet, listed at 11.35 pounds and 12 inches wide, says only that it is pre-seasoned.

Read together, the five descriptions cover vegetable oil, flaxseed oil, a proprietary blend and an unnamed preseasoning. None of them publishes a trans fat figure, and none of them describes hydrogenated oil as an ingredient.

Re-seasoning at home with vegetable oil

If you season a skillet yourself, you are applying the same process the makers describe: a thin coat of oil, heated until it bonds. Lodge’s care line is to hand wash, dry and rub with cooking oil, which is a maintenance coat rather than a full re-season. EDGING CASTING advises cleaning by hand in warm water, drying completely, and seasoning with natural oils, and warns against the dishwasher and against air drying.

Backcountry Iron gives the most detailed care text of the five: keep the pan out of the dishwasher, do not soak it overnight, do not air dry, scrape stuck food with a flat utensil, wipe dry immediately and apply a new layer of oil to protect from rust. It also mentions a stainless steel chainmail scrubber for smoothing the surface.

None of these care instructions mentions trans fat, and none specifies a particular vegetable oil by brand or type. The instructions describe oil as a protective and release coating, applied thin and bonded by heat.

The skillets themselves, by the published figures

The five picks differ widely in size and weight, which matters more for daily cooking than the seasoning question. Lodge lists 10.25 inches in diameter and 5.35 pounds. Victoria lists a 10 inch pan at 4.8 pounds. Backcountry Iron lists a 12 inch pan at 7.0 pounds, with a stated 12.25 inch diameter, 12.75 inches spout to spout and a handle length of 4.75 inches. Cuisinel lists a 12 inch pan at 11.35 pounds. EDGING CASTING lists a 17 inch pan at 14.75 pounds.

Height figures are published too: 2.0 inches for the Lodge, 2.75 inches for the Victoria, 3.4 inches for the Backcountry Iron, 3.0 inches for the Cuisinel and 2.95 inches for the EDGING CASTING. Width and depth figures for each pan appear on the guide page.

Heat sources are covered by all five. Lodge states the skillet works in the oven, on the stove, on the grill, over a campfire and on induction cooktops. Victoria, Backcountry Iron, Cuisinel and EDGING CASTING each state compatibility with gas, electric or induction cooking and with oven or outdoor use. Those statements are about the iron, not the seasoning.

The bottom line on vegetable oil and trans fats

Seasoning with vegetable oil leaves a bonded polymer layer on the iron. The makers of the five skillets compared here describe vegetable oil, flaxseed oil or a proprietary blend as the seasoning medium, and two of them state that no synthetic coatings or chemicals are used. None publishes a trans fat figure for the seasoning.

If a trans fat number matters to you, the honest position is that this site has not compared one for these skillets, because the makers do not publish it. What is published is the oil type, the care routine and the physical dimensions of each pan. Those are the figures you can check against the guide.