[TheForge] Identifying Wrought Iron

[Andrew Vida]

Jim Beard wrote:
> Howdy Kind Folks!
> 
> Now that the domain is working again...  I had a question about
> identifying wrought iron.  Whats the best way to go about it? 

	Metallographic analysis.  Oh, you mean the best cheap, easy, and 
practical way?  That's different.

	This list REALLY needs a FAQ.  That said, I do do this one mo' time.

	The definition if "wrought iron" is not really rigorous, but for 
conversational purposes we may say that it is a mixture of nearly pure 
iron with a greater or lesser amount of iron silicate added to it. 
Analysis of various wrought iron samples from different places and times 
reveal that there is some non-trivial variance in the analyses, but the 
major components being iron and iron silicate seems to be a universal fact.

	One way to test for wrought iron is by visual inspection of corroded 
material.  Because of the mode of manufacture, wrought iron forms 
longitudinal fibers of iron and silicate.  The iron component will etch 
away in a corrosive environment at a rate significantly faster than the 
silicates, thereby exposing the stratified, grainy, at times wood-like 
structure of the material.

	The spark test is another where one takes a sample to a grinding wheel 
and observes the character of the sparks coming off the wheel.  Wrought 
iron sparks a dark orange color with single-pointed streamers.  Compare 
this with tool steel, which sparks bright yellow and whose streamers 
burst in a star-pattern at their ends, like fireworks exploding at the 
top of their paths.

	The break test is another simple once that is often described by 
instructing the tester to saw halfway through a sample, say, 1/2 to 3/4 
inch thick, then bend at the kerf to failure.  If the sample is wrought 
iron, you will observe a very fibrous structure at the breakage site. 
Compared with steel, wrought iron is quite unique.  Steel, even in a 
poor state of heat treat (excessive grain size, e.g.) fails in a manner 
that reveals that grainy crystal structure rather than one of long fibers.

	None of these tests taken singly can be regarded as conclusive, but 
taken as a set tend to be pretty reliable.  One possible exception is in 
the case of blister steel because it is carburized wrought iron.  It is 
there fore possible to have an object with grain like wrought but sparks 
like steel.  I'm not positive, but I think that the same may the case 
with crucible steel, which also starts with wrought, but I am not 
certain of this.  Maybe Bill Hochella could clarify this?

 > I'm
> assuming you want to be able to see the grain to
> actually tell, so cutting it would likely be the easiest way?  What
> about filing down the surface?  Would that expose grains in wrought if
> they were there?

	Not likely.
> 
> I'm rather new to smithing (being beating hot iron once a week or so
> for the last year at a friends forge) and as such don't have much
> experience identifying metals.  Last week however, I was out at the
> local steel scrap yard (I try to go once a month or so), and found a
> few large chain links.  The links were over a foot or more long, and
> the metal was about 1.5" in diameter.  The metal had been painted over
> (i think) and was covered in a thick layer of dirt.  I couldn't really
> see the surface of the metal.  However, it did seem like it had a
> grain to it.  Almost like the surface was one of a tree branch.  The
> links look like they had been lap welded on one end (as opposed to the
> middle of a side, which is what I have seen examples of..).  Anyway, I
> wondered if these were old Wrought Iron links..

	Sounds suspiciously like wrought iron.  Did you take them?
> 
> Also (I'm sure this is a can of worms here) but I've read some
> information about Wrought that says it was not as nice to forge as
> mild steel, yet I hear smiths talk about finding it and liking it too,
> so I'm a bit confused.  Is it easy / hard / fun / boring to forge
> with?

	If you don't know how to forge wrought, you will have fits with it. 
Most smiths that I know of hate wrought iron.  A few, such as myself, 
are fond of it.  If you are doing work that would benefit from the 
"authenticity" of wrought iron, then by all means use it.  Otherwise I 
would stick to mild steel, unless wrought is something you decide that 
you love or otherwise have to master, neither of which are unworthy 
reasons for pursuing wrought iron.

	I'm finisheing up another wrought iron bracelet as I type this.  It is 
sitting in the acid right at the moment.

	Good luck.

	-Andy