doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Iron, Steel & Alloy Staining

Thanks much Doc Drew. Back to your 25x micrograph, there is the appearance that the body of the darker etching material and the body of the lighter material are fairly uniform. The grain seems to have the appearance of significant heat affect where the forge weld joins the two.

Looking forward to the article. Hope you etched that Ithaca Crass defect. I'd guess that was at a major weld failure, a manufacturing defect, rather than a material inclusion.

Practical Hints on Shooting, K. Paul Trench, 1887, �Barrels�
https://books.google.com/books?id=xrwUAAAAYAAJ&pg=PA20&lpg
Pour a drop of nitric acid of 1.2 specific gravity on the barrel, and allow it to remain there for a few seconds; then wipe it off with a piece of chamois-leather. On iron this leaves a light-grey spot, but on steel a much darker one�almost black.

And yet just a few paragraphs later, the author makes a contradictory statement. It seems that �somber hue� is meant to indicate a dark coloration. No wonder there is so much confusion on this subject.


The wavy water-lines so much admired in Damascus originate from the twisted metal, and are brought out by immersing the tubes in dilute acids, the corrosive action of which, operating differently on the iron and steel, causes the former to become of a somber hue, and the latter almost white.

Ya' think the English were just messin' with us

W.W. Greener "Manufacture of Iron for Gun Barrels"
http://books.google.com/books?id=LAsAAAAAQAAJ
"It is the twisting of the different metals that gives the various figures in the finished barrel. The steel being hard resists the acids, and retains a white or light brown hue, whilst the iron, or softer metal, is so acted upon by the acid as to be changed into a dark brown or black colour."

I�ve found that it is wise to take most old writings with a grain of salt. Not just the Brit�s. It seems that many early authors were not so much interested in being correct, as they were in making sure that no one challenged their assertions. The typical methodology was to make a statement of �fact�, declare yourself to be the supreme expert on the subject and then dare anyone else to say you were wrong. Sort of like being the biggest literary bully on the block.

I typically look for other knowledgeable contemporary authors to corroborate a statement made by one. Then this mutually agreed upon �fact�, must be weighed against what we know to be the scientific and metallurgical knowledge of the time. Just because several old authors agree on a subject, does not make it so. Case in point; the concept that cold hammering of steel will make it more dense.

"seems that many early authors were not so much interested in being correct, as they were in making sure that no one challenged their assertions. The typical methodology was to make a statement of �fact�, declare yourself to be the supreme expert on the subject and then dare anyone else to say you were wrong. Sort of like being the biggest literary bully on the block."


I'm sure glad we've all moved beyond that!!

Sounds as though the jury is still out on the question of whether it is the iron or the steel that ends up white after rusting and etching. There are still totally conflicting views on the matter, and I imagine that isn't going to change any time soon. Much of what has been written will be taken as gospel for decades even if it is incorrect, just as the idea that Damascus barrels are all ticking time-bombs one shell away from becoming a deadly grenade.

In the recent Composite Barrel thread, I was of the opinion that the only way to settle this would be to rust, boil, card, and etch samples of steel and wrought iron to actually see which material was most resistant to a ferric chloride etch, and which one had the staining most easily removed by the same ferric chloride etch. So the question for me at least is where to get some small pieces of wrought iron that are consistent with what nineteenth century Damascus barrel makers used. I'm assuming any relatively low carbon steel would suffice for the steel samples. I can get horseshoe nails at the local tack shop, but I have no way of knowing if they are made of wrought iron or steel. Then there is the question Steve Culver raised about different rusting processes giving different results after the etch.



I note that Steve wrote "THEORY" in capital letters, and I agree with him that the iron ends up white. In my limited experience with rust bluing and browning, the entire barrel seems to rust or stain relatively equally and evenly if I have done a good job of prep, and it is only after etching and carding that contrast between the iron and steel of Damascus becomes readily apparent. I've always assumed then that one or the other was simply more susceptible to having the staining or rusting oxide removed by the ferric chloride. And I've always assumed that is was the iron portion that ends up white if the etch is performed properly. But assuming or perceiving doesn't give us a definitive answer as to which material ends up white. I suppose a metallurgist could take a sample of finished barrel and tell us which part was the iron and which was the steel. I suppose it may not really matter as long as we get our contrast and bring out those attractive patterns, but it would be nice to know for sure.

We know that a "too concentrated" etch or a "too long" etch can remove all color and actually begin to eat the surface to the point where it can be seen and felt on the barrels, and this is also why we coat or plug the bores to protect the bare metal from the etch. I have stuck with very short etch times in a horizontal trough to minimize the chance of removing all of the color that I worked hard to get. But then, I never noticed that the weld boundary can end up either white or dark, and have no good explanation of why that would happen. As some food for thought, I'll toss out the idea that the final color of the weld joints could have more to do with the actual weld process, i.e., temperature, flux (if used), amount of scale formation, etc. than it has to do with the chemicals used in the rusting process. That's just a theory with absolutely zero facts to support it.

Keith, real wrought iron is available, but it's not likely to be sold in the form of a modern manufactured item. It's not so hard to find, reclaimed raw bar stock, most likely from an old bridge or building tear down, or maybe 1800's maritime chain links. There's a shade tree test that works pretty decent, make a partial cut in a bar, then try to break it with a sharp 90* hammer hit. Wrought will tend to show characteristic stringing.

I think antique wrought would be a decent example of what might be in a gun barrel. I'd have my doubts if a true simple steel was readily available to simulate what might have been around back when. Steve may have some wrought in his shop, and I wouldn't be surprised if he might not have tried an etch or two. While a too long etch on a barrel would not be a good idea, it may just be an exaggerated example of the differences in materials that it takes to show a color difference.

I have some wrought iron in my shop and of course a good selection of steels. I should be able to source any type of steel that I don�t have, through my suppliers. I would be happy to provide wrought iron and steel samples for testing. But rather than test the iron and steel separately, it may be better to have them made up into damascus. I could easily make some. I believe the test would be more accurate, if the two materials were welded together and subjected to testing simultaneously, rather than separately. Seconds matter in the finishing process. Treating them separately, could result in errors.

I�m thinking a low layer count (maybe 11 layers) forge welded, twisted and then flattened out into bar stock. I could forge the welded rod to around 1 inch square before twisting, rather than the approximately 3/8 inch that was used in gun barrels. The larger stock and broader damascus pattern would make identifying the iron and steel layers easier.

This issue with this plan, is whether the alloy content of the iron and steel that I use, matches the materials used in gun barrels. We have no good records of what the Belgians used. I have wondered if there were any records left of British production. I sent an email to Graham Greener a few years ago, asking if there were any old records from Greener�s damascus manufacturing. He never responded to me. Maybe someone here has a significant enough presence to get Graham�s attention and secure a response from him?

As far as the wrought iron, I have some anchor chain and wagon tire material. I suspect that the silica content of the anchor chain and wagon tire iron is higher than would be used for gun barrels. Though, I have not a clue. I can restack and weld the iron to reduce the silica content; same as was done in the piling process of long ago. But, I have no idea what I am shooting for in the final product and not sure of a method for testing the material for silica content.

The steel is a similar issue. What was the alloy content of gun barrel steel and what modern steel approximates that alloying?? Drew had some barrel steel tested. But, is that one sample fully representative of the gun barrel industry? It�s hard to argue against test results, but I found it quite surprising that the steel in the barrel was determined to be of very low carbon content. I expected that the barrel manufacturers would have used steel in the .4 to .7 carbon range. Perhaps I am totally wrong, but this is the reason why I am concerned that one testing result may not be completely representative of the industry.

There is one other possibility for analyzing this question. Perhaps I just need to go look at a bunch of damascus barrels. I have a rough barrel tube, which I purchased from Peter Dyson. I did a light etch on the tube with ferric chloride. This I did by simply using a rag to wipe a fairly strong solution of FC on the tube. The steel quickly turned dark, while the iron remained white. Certainly, this etch is not truly representative of the rust and etch process. But after etching, I used a small battery powered magnifier to examine the tube. It was very easy for me to tell the iron from the steel, by their different grain structure. There is a gun shop in Olathe, KS, which typically has about 100 damascus barreled guns in inventory. Maybe I just need to get myself over to Olathe with my little magnifier, and examine a bunch of guns to see if I can identify the iron and steel layers and their coloration.

Weld lines�� Yet another quandary.
I have a variety of suppositions on this topic, but no solid evidence to support my thoughts. I�m not going to share my musings, lest I just confuse everyone. The necessary information will be found at the molecular level. I know of no in depth analysis having ever been done on forge weld lines. But, I know exactly the guy to ask. He has the expertise and the equipment to do the testing. But, he is very busy and often takes a while to respond. I�ll yank his chain and see if he can help.

Only thoughts Steve. Instead of flattening the twist into a bar, a barrel might have more likely been ground to shape. A forged bar might end up with spots of long thin tapered laps of the two materials, where you may be looking for slices somewhere in the middle.

I've also noticed when wrought is heavily etched, the stringy appearance is easy to see. Doc Drew's pictures show tiny islands of slag pretty evenly distributed. I've always suspected that is the reason and result of the heavy drawing to produce a barrel, distribute and mitigate inclusions or defects.