Thread: Coating inside a Japanese cast Iron Tea Pot

SWMBO has a traditional cast iron Japanese tea pot that she has used regularly for 25 years. The brew is kept warm by a small spirit burner and it is has only ever been hand washed.

Inside the surface is coated with some a black layer of something that obviously resists water and tea but last week it developed some rust spots.
Anyone have a idea what that coating might be?

Tpot.jpg

Bob,
This might be stating the obvious, but all my cast iron cookware needs conditioning before use. Typically the item is heated in an oven having first had oil wiped on the cooking surface, then allowed to cool, then re oiled and heated again. The process is repeated until a very hard black coating is built up. This coating provides a non-stick and corrosion resistant surface.

Could this be what was in your tea pot? My guess is that the tannins in the tea eventually got through the original coating to the iron.

Graham.

For more information, see for example: https://www.youtube.com/watch?v=O6bFWVB2BRY

Graham.

Originally Posted by Oldbikerider

Bob,
This might be stating the obvious, but all my cast iron cookware needs conditioning before use. Typically the item is heated in an oven having first had oil wiped on the cooking surface, then allowed to cool, then re oiled and heated again. The process is repeated until a very hard black coating is built up. This coating provides a non-stick and corrosion resistant surface.

Could this be what was in your tea pot? My guess is that the tannins in the tea eventually got through the original coating to the iron.

Graham.

Thanks - sounds like a goes, being japanese I suspect they use rice oil.

[EDIT] I looked it up - they use sesame oil.
Natural Import Company - Traditional Japanese foods - How to Care for your Japanese Cast Iron

I use olive oil, it's relatively tasteless. Others have told me that pig fat (bacon rind) is preferred in Europe.

For a frying pan it's important to use an oil with a high smoke point (eg. olive oil) because the cooking temperature will be high, but I guess for a teapot where it will be at 100 Deg max. the oil choice is not too critical.

Graham.

Originally Posted by Oldbikerider

I use olive oil, it's relatively tasteless. Others have told me that pig fat (bacon rind) is preferred in Europe.

For a frying pan it's important to use an oil with a high smoke point (eg. olive oil) because the cooking temperature will be high, but I guess for a teapot where it will be at 100 Deg max. the oil choice is not too critical.

Graham.

My understanding is that Olive oil has a relatively low smoke point compared to rice bran oil, and to get maximum benefit from olive oil it should be used raw, as cooking destroys many of its natural benefits.

Depends on the olive oil. Tables of smoke point for cooking oils on the internet are ambiguous. A mate of mine (French, and a professional chef for 40 years) told me to use olive oil, or pig fat, that's good enough for me. My pans have kept their coating for 30 years. For frypan conditioning you don't care about preserving any nutrients, it's just the glazing properties. I also have stainless steel pans and always give them a high temp blast with olive oil before cooling down for cooking, this results in a teflon-like non-stick surface.

I think for a teapot anything is going to work because of the low temperatures encountered. Sesame oil sounds like fun!

Graham.

I was told the best oil to season a pan are a group of oils called Drying Oils, e.g. linseed, sunflower, poppy and walnut oil fall into this category of drying vegetable oils. my missus buys stoneware so I've never actually tried to season a cast iron pan with them, but the theory behind it seems sound.

The rim looks like it’s glazed. Are you sure it isn’t glazed on the inside Bob? I have cast iron baking pans that look like they are oiled, but it’s actually black glazing.

Originally Posted by jack620

The rim looks like it’s glazed. Are you sure it isn’t glazed on the inside Bob? I have cast iron baking pans that look like they are oiled, but it’s actually black glazing.

Could be. There is a local ceramic society not far from our mens shed. Might drop in and ask there.

Hi BobL,
I am pretty sure it is japanning.

https://en.wikipedia.org/wiki/Japan_black

Basically, it is an asphaltum based coating which dries hard and is good for treatment of water bearing metal vessels,says Wiki.

The blokes that do up old cast iron wood planes use it.

RexMill.com Hand Planes 101 The Resource

Wether or not the materials are still available is another question. <EDIT-this guys may have something - http://www.barnes.com.au/files/sn_product_guide.pdf >

Grahame

Bob,

We have two cast iron teapots, one a traditional tetsubin purchased thirty years ago, the other a modern variation, purchased a few years ago. The later appears to have a vitreous internal coating while the older pot's internal finish is similar to yours. A dig around online suggests that the older pots were not coated because the iron imparted it own taste in the tea. Maybe the taste of bit of iron oxide might be preferable to any oil coating.

Bob.

Bob,

This clip shows the application of the traditional Japanese pot's external finish and mentions the coating of the interior with an oxide layer around the 11 minute mark - https://www.youtube.com/watch?v=o6AuxztRkYM&t=246s

Bob.