Cast iron skillet (for tsuba) experiment!

[Dan tsuba]

Question, if tsuba were made from cast iron in the Edo period, could they be abraded to appear smooth (as if they were hand forged)? 

 

I was going to try this with my sand cast bottle opener I bought from Japan.  I refer you to page 8 of my “Tsuba casting molds?” thread (that would be November 18^th, 2022).

 

But that bottle opener was just too nice to ruin it by sanding it.  But I still use it to open bottles of beer (I think I will have one after I post this because my arm is tired from sanding!)

 

So, today’s experiment is to see if a piece of sand cast cast-iron can be abraded to appear smooth.

 

Pictures of the experiment are included below.

 

From the internet-

“A proprietary mix of molten pig iron, steel and other ingredients are poured into a mold made of sand. Since sand melts at a higher temperature than iron, the mold holds its shape. Once the cast iron pan or pot has cooled, the sand mold is broken, leaving behind a brand-new piece of cast iron cookware.”

 

So, we know that a cast iron skillet is sand cast.  And yes, I looked at videos on You Tube to make sure that is how it is done.

 

I bought a cast iron skillet at Walmart.  Only cost $8.00 U.S., so it was a great price!

 

I had some #60 grit sandpaper, and I went to work sanding a small part of the back of the skillet by hand (no power tools used!).

 

It took about an hour and a half, and I concentrated on an area on the back side of the skillet that was about 3 inches by 1 ¾ inches.

 

It smoothed out nicely and the results can be seen below.

 

So, what did this experiment prove?

 

Well, firstly, that I am an old retired guy with nothing better to do but to sand a cast iron skillet!

 

And we all know that rough metal can be abraded to get it smooth.

 

So, I proved nothing!

 

Not really, just kidding!

 

I will use these pictures in the future to compare the surface texture of tsuba that I may purchase to the surface texture of my abraded cast iron skillet.

If they appear to be a close match, the odds that the tsuba is made from cast iron are pretty good!

 

Anyway, the good news is that I can still use the skillet to cook with.  Even though I tried to use a large sledgehammer (several times!) to break off the handle to show some members what a broken piece of cast iron looks like.

 

Several members have stated in the past that cast iron is very brittle and will break when hit.  Not my cast iron skillet!

 

Onward!

 

[Brian]

You're seriously comparing modern "cast" with the technique done 200-300 years ago?
The 2 have almost nothing in common.

[Dan tsuba]

Well,

 

Seeing that I can’t afford an original Edo period kettle, I have to do the best with what I have!

 

Maybe another member (or members?) that have a spare Edo period kettle hanging around (that they don’t want anymore) can try sanding that to see how the sanded cast iron appears and then take a sledgehammer to the kettle to see if it breaks apart.

 

My experiment may not be perfect, but heck, at least I am trying!

[Jake6500]

10 hours ago, Dan tsuba said:

Well,

 

Seeing that I can’t afford an original Edo period kettle, I have to do the best with what I have!

 

Maybe another member (or members?) that have a spare Edo period kettle hanging around (that they don’t want anymore) can try sanding that to see how the sanded cast iron appears and then take a sledgehammer to the kettle to see if it breaks apart.

 

My experiment may not be perfect, but heck, at least I am trying!

 

I would love to assist in your experiments but the thought of actually doing that with a piece of history makes me feel physical pain...

[Dan tsuba]

Thanks Jake!

 

I agree!  

 

So what is the solution to this enigma?

 

Onward my friend, and with respect,

Dan

 

[Jesta]

Hi, 2 cents from me

One possible solution would be to find a modern smith who still practices casting techniques that are the same as those used in the past. There are a number of people, such as Tod’s Workshop (see YouTube), who are into making weapons and armour the old way, and then stress-testing it. They might have some advice on how to replicate cast pieces, or be able to create one for you. If the form is not important, then just get a piece for experimentation. 

Now you have a modern piece sanded down you could compare that with the one from the older practice to see if there are significant differences. 

 

On a related note: You could get a modern cast tsuba and see if you could sand it to make it appear closer to a genuine Edot one… 

[Robert S]

I've done casting, and good castings can definitely be smoothed and fine tuned to the point that they would look (and practically are) carved.  However, poor castings would still have micro flaws which would be evident, and clearly different types of flaws than forged iron.  So it depends on the skill of the caster.  The metal would still be significantly different in microstructure and/or chemistry, but you'd be unlikely to know without destructive testing (not recommended :-) ), unless you have access to some pretty sophisticated equipment.

[Dan tsuba]

Thanks Robert for the information and your assistance and support!

Much appreciated!

 

With respect,

Dan

 

Addendum-

So, Robert.

What are your thoughts that non-destructive metallurgical testing would be the only way to determine if a tsuba is made from cast iron or is hand forged (without destroying the tsuba)?

[Robert S]

Dan:

 

I don't think it's the only way of determining whether something is cast, since usually the subsequent clean-up on a casting has not been done to the level we were discussing, or the casting contains obvious flaws, and it's pretty obviously cast.  But if someone really had subsequently worked a high quality casting to the point that all casting marks and characteristics had been removed, then you'd have to know more about the specific metallurgy of irons used for casting versus forging at that time, as well as what chemical changes (for instance, carbon content changes) occurred as a result of forging.  I've seen information on this from people who are expert metallurgists... which I am not :-)

 

Robert S

[Dan tsuba]

So, in my first post on this thread I wanted to show members what a broken piece of cast iron looks like.

 

Well, a broken cast iron tsuba is shown in picture number 1 and 2 below.

 

Compare those pictures (showing small grainy or sand type raised and lowered areas) to another cast iron tsuba shown below.  That other cast iron tsuba was shown on my post on p. 12 of my "Tsuba casting molds?" thread. (and yes, we all remember that thread!) -with explanation on June 26, 2023- picture 3 below-which you might have to zoom in on.   And let us not forget that I show pictures and state a reference here, unlike many members on that privously mentioned thread (oh well, let's not go there!).

 

I know that is a tiny area of that particular tsuba that was chipped off (on purpose if you read the post), but you can still notice the sand type texture of that exposed tiny piece.

 

So, my opinion is that the picture of that chipped tsuba referred to above is a cast iron tsuba.

 

I am pretty sure it would take a lot more effort to chip a small piece from a wrought iron tsuba than it would to chip a small piece from a cast iron tsuba (since cast iron is very brittle).

 

Pictures number 4, 5 and 6 shows a different broken cast iron tsuba for comparison (smaller areas of cast iron shown).

 

Now compare those pictures to the broken piece picture of wrought iron shown below (picture number 7).

 

Big difference!

 

A good website that explains and shows several pictures of broken wrought iron is shown below (I got the picture from that website)-

 

https://islandblacks...st-for-wrought-iron/

 

Anyway, the good news is that I didn’t have to break my cast iron skillet to show what a broken piece of cast iron looks like!

 

Hurrah!

 

(and as a side note- I did not damage any of the tsuba shown.  All pictures are from the internet!)

 

 

[Robert S]

Dan Tsuba:

 

That's a great example of the characteristics of cast iron which are evident with destructive testing.  Not of course something most of us would prefer as a testing method, but it does happen!

 

Robert S