The finishing.com Hotline: Serious Education ... plus the most fun you can have in metal finishing. Ted Mooney, Webmaster
Inside of Cast Iron Tea Kettle Rusts
An ongoing discussion from 2003 through 2016 . . .(2003)
Q. I was given a cast iron tea kettle. We used it two winters on top of our wood stove to put water/potpourri in for fragrance. The inside of the tea kettle is rusting. I have washed it, tried soaking cooking oil in it (to season it) like you do a cast iron skillet, yet it is still rusting and flaking. I am sure this is not good to be putting rust water steam out in the air for us to breathe. We love this cast iron tea kettle and it is perfect for wood stove use. Any suggestions on how to get rust out and keep it out so we may continue to use it would be greatly appreciated.
Thank You,Becky Wilmoth
hobbyist - Salem, Illinois
A. I would expect the water to vaporize off and the metal to stay behind, Becky; but in any case I would not have any concern from a health standpoint about the rust getting into the air. Your seasoning method offers at best very temporary protection. Distilled water would contain no salt and might be slightly less corrosive.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
I just refinished a cast iron kettle for the same reason. coat inside and out with olive oil and bake in the oven, or, as we did, put it on the bar-b-q (with a cover) and let it cook. The first coat will be more of a grey color. After it cools, coat again and bake again. Each coat will get darker, until you have a nice black finish. Regular vegetable oil won't work. It must be olive oil. I sand blasted the pot first, easier to do the inside, but wire brushing to remove most of the rust first should work.
Good luck,Ed Kay
- St. Louis, Missouri
Q. I was wondering as I read Ed Kay - St. Louis, Missouri, USA, how long he "cooked" the cast iron kettle for? I have one that belonged to my dad that passed sway in 1998 and want to us use it this winter on the wood stove.Valerie Harris
- Richmond, Virginia
A. The time it takes to season a Tea Kettle in the oven probably varies. I know that I put my skillets in a 350 degree oven for 2 hours at a time. I wouldn't use olive oil or other liquid oils because they can go rancid and they also leave a sticky residue (I know this from experience). I have heard lard or other animal fat is the best oil to use, but I have successfully used Crisco solid vegetable shortening.Robert Scott
- Portland, Pennsylvania
A. After some research, I've found that the best oil for cast iron seasoning is coconut oil =>
because it is less likely to go rancid and sustains higher heat than other types of oil. By contrast, although olive oil seems to be popular with cast iron cooks, if you read cooking web sites and related health info., olive oil is one of the least heat resistant oils in terms of retaining its healthful properties under heat.
Rust is a problem if the cast iron item in question isn't used regularly or a tight fitting lid prevents proper air circulation (applicable to kettles and dutch ovens, in particular). If there are signs of rust or a metallic smell, it is time to scrub off that rust with steel wool [linked by editor to product info at Rockler] -- which according to some may be easier to remove if you pre-treat using the self-cleaning cycle of your oven to carbonize the existing seasoning for easier removal -- re-coat with a thin layer of coconut oil, and heat in an oven at 350-degrees in an inverted position, with lid off, also coated inside and out (with foil or a baking sheet to catch any stray drippings beneath the rack). Cool and repeat up to four times to build up a protective barrier. As per the Lodge Co. instructions, each time you use cast iron, avoid soap as that will strip the seasoning. Instead, clean with hot water, a stiff brush and reapply a light coating of oil while the cast iron is still warm after every use to restore the finish. (This applies to their pre-seasoned as well as their unseasoned cookware.)
Other tips: Do not leave the lid on a cast iron tea kettle or dutch oven but instead use a paper towel or cloth to keep the lid from making an airtight seal. Finally, do not leave any cast iron cookware to air dry. Even a small amount of moisture will lead to rust.Diana Lynn
- Whittier, California
November 10, 2009
A. Easiest way to season cast iron is a 3 step process,
1-Scrub & Wash your cast iron work/pan/kettle...
2-Boil tea leaves in it.
3-Dry Fry coconut meat and once its cold, dry fry coconut meat again, and again, and again several time until your cast iron is black.
work great for me :)
- Kedah Malaysia
A. I recently had a stack of cast iron skillets to season after using electrolysis to de-rust them. Searching on the internet finds lots of different methods that people swear by, but no definitive answer. I finally ran across this:
Essentially she proposes that an oil that will polymerize the best will provide the most durable coating.
has smoke points of various oils.
I've been experimenting with flax seed oil =>
and can say that cooking at too high a temperature above the smoke point doesn't work, but about 100 degrees F seems to do the trick (325 for my flax oil). It creates an amber colored coating that seems to be super hard and very non-stick.
- Kansas City, Missouri
February 17, 2011
A. OK, take hands off pot, and back away slowly. I saw no advice listed you should do to a cast iron tea pot.
Ignore the rust for now. Fill the pot about 1/2 full of regular water and bring to a boil on the stove until almost empty. Let that set until the sides are cooled down to the touch, and then empty the last drops from the pot. Dry with a clean rag. Refill it again, and repeat the above method 5-6 times, each time letting it steam the water away. You should start to see a white calcium build up start inside the pot. That is what is going to stop the rust, the calcium coming from the water. I am not sure if you can speed this with a calcium pill added to the water or not. The slow way maybe the best way to build up the seal inside.
Now do this a few times using loose tea. A couple of spoonfuls of loose tea to each quart of water. (Less messy if you put in tea-ball.) Cool down, and these times let the tea water evaporate, then dry with a "soft" towel. Never use abrasives in the pot as that cuts the calcium deposits you want to stop the rust. You can also use these tea waters on the exterior of the pot to shine it with a soft cloth. Not even a sponge!
No steel wool, no dish washer, no olive oil or seasoning oil -- just clean water & soft cloth and continued use will make your cast iron tea pot happy.
- Stockton, California USA
April 25, 2011
Q. Dear Shintao Boadism, do you know this for sure? I have tried everything from steel wool to washing soda, salt, oil, vinegar... and my (not enameled) cast iron tea pot is giving off more black stuff than ever! This started after I put the pot on a very low gas flame to dry it after use...and walked out of the kitchen. The pot is gave me excellent service for nearly 30 years until then. Looking for some good advice on how to fix it. Many thanks!
- Cape Town, South Africa
A. First off you never NEVER season in olive oil NEVER!!
Just soak it in coke for an hour and a half to two hours
After, just wipe it out and repeat if needed. That's all you will have to do.
- Sevierville Tennessee USA
November 2, 2011
Q. Regarding the cast iron tea pot questions and answers. I recently bought a very old cast iron tea pot that is covered inside with rust. I want to use it to make tea. I read the different methods, especially the one about boiling water numerous times and then using tea to build up calcium. My question is; since the tea pot has so much rust do I need to get the rust out first ( and how would I do this) before I do the boiling methods, or will this remove all the rust? Should I put the coke in first, as I assume this will remove the rust? and then boil the water/tea? I already did boil water 3 times and when I wipe out the pot black stuff continues to come off. Thanks for any help as I really want to use this pot to brew tea and paid a good penny for it.Janice Smith
- Gainesville, Florida, USA
A. I have had excellent results removing rust on a kettle using vinegar. 2 parts vinegar 1 part water. It takes a while but it works great.Rick Sledge
- Roanoke, Alabama, USA
January 24, 2012
! When I was a boy there was no such thing as iron deficiency in women, but they all used to have mottled legs from sitting in front of the fire.
I use my cast iron kettle on wood burning stove all the time. It made a lovely cup of tea, very dark and rust coloured. My daughter would not drink it, so I use the water now for a hot water bottle.
- Northop, North Wales
May 14, 2012
Q. I have a cast iron tea kettle that has been out on my porch for five years it is peeling paint and rusting and I want to clean it up to bring it in to use it for aroma therapy on my electric stove. Is that possible? How do I get the rust and peeling paint off? Do I use a wire brush? Do I use a chemical to clean my cast iron kettle? Then do I season it? Please help me!cathi carlson
- Mentor Ohio USA
Hi Cathi. I think the paint will come off with steel wool, sandpaper, or wire brush. If it's too much work to do by hand, a battery operated portable drill can be fitted with any of the above tools. I wouldn't use paint removers.
After that, well, what can I say that could possibly herd together the divergent (and even intolerant) seasoning advice you've read on this page? :-)
You'll have to believe somebody and follow their advice, and dismiss everyone else who says they're wrong :-)
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Q. My friend has a porcelain teapot that developed a pinhole,
I sanded porcelain and rust with a Dremel tool the size of a quarter, and put JB Weld on pinhole which sealed the hole; but now rusty water develops over a weeks time, what can I cover the repaired area with?
- Rocker, Montana, USA
April 9, 2014
A. Tom, you can go to Kmart and they sell an enamel repair kit. It costs about $9. It goes on like nail polish.Carol Thomas
- Ferndale, Washington
February 12, 2016
A. Some interesting advice on cleaning and treating cast iron. Looking at the original question, first to clean the kettle, then to seal it.
Cast iron is just that, iron. So, when it comes into contact with an oxidizer it will rust. Cleaning it will depend on how bad the rust is. If it has begun to flake, you will probably need a good stiff bristle brush (nylon, or similar) to clean off the larger flakes. If it isn't too bad, or after cleaning the larger flakes off, use fine steel wool. A mild acid, such as cola or vinegar, or a commercial product, such as CLR, will help remove milder rust. Be sure to rinse thoroughly.
Now, to prevent more rust, the iron needs to be sealed, or protected. The "calcification" suggestion certainly looks good in theory. And, if you are only using this to heat water, it may work fine. However, your water would need to contain calcium. If you have a water softener/conditioner, it won't have enough. And, if you're going to cook food in it (kettles work well for soups and stews), you will need to properly season it. The best way to seal cast iron is with oil or grease. Any food grade oil will work, however, oils with low smoke temperatures, like olive oil, create a large amount of smoke and tend to be more difficult to get the desired effect. Flax oil has become popular amongst cast iron users, although I have never tried it. I use either shortening or coconut oil, or a combination of both. Once the iron is clean, coat the kettle, inside and out, with oil. Then place in a cold oven and heat to about 200 degrees F, and leave in for about 2 to 3 hours. Remove, cool, and wipe off excess oil. Lightly oil again and place in a cold oven and heat to 350 - 400 degree F and leave in for 1 to 2 hours. Remove, cool, and wipe off excess oil. This should give you the nice black coating and texture we are all familiar with. Periodically, it will need to be cleaned with some hot water (no soap, as soap takes away the coating), and a light coating of oil/grease reapplied, and reheated on the stove.
That should keep your kettle good to use for many years to come.
- Howell, Michigan
March 9, 2016
A. Cast Iron tea pots are iron and will rust.
This explanation is a little simplified, but the basic ideas are true. There are two types of rust. The red kind that is like cancer and keeps spreading and the black kind that seals. The bluing used on gun barrels is actually the black rust. Coke contains phosphoric acid. Phosphoric acid is used in rust removal and converts red rust to black rust.
For seasoning teapots, I would scrub the inside a little to remove any flaky deposits and then boil a cola product in it. This will convert any remaining rust into the black form and create a protective barrier. Using the oil seasoning process is fine for the outside, but produces off flavors on the inside. (More so than the actual iron)
When used with regular tea, the acid in tea will help keep the iron seasoned with the black rust. But it will also leach some of the iron into the tea. This can flavor the tea and some people find the flavor off-putting, hence the prevalence of enamel lined teapots. When used as an infuser or humidifier, you will be concentrating the chemicals in the water you are using. The higher concentrations can speed up the oxidation process and produce noticeable red rust. This rust will not cause health issues to people breathing the moisture, but can eventually destroy the pot. Enamel lined pots might be better for this use than unlined pots. There will be a build up of white particular from the evaporated water inside which ever pot is used, unless distilled water is used exclusively. This build up may be colored by the rust from the pot. The scaling is similar to what is inside a humidifier that uses the heat method over the ultrasonic vaporizing process.
- Columbia, Maryland
April 28, 2016
A. I would like to throw 2 cents worth of thought on care and seasoning of cast iron in general.
In the 1800s and early 1900s all anyone had to season these pots and kettles with was bacon grease. I have tried all the others, and nothing seems to work as well as bacon grease. You can remove rust with it, season with it, protect the iron with it. Sometimes the old ways are the best.
- Liberty Hill, Texas
May 14, 2016
In those same olden days the docs treated a large number of diseases and conditions with mercury (like syphilis which had a survival rate of <1% before penicillin) . Keep in mind, the old ways are not always the best ways...Col Davy
- Aldi, Australia