color case question

[Jim Kibler]

I think that all of your points, DWS, are valid except perhaps "E".   Point "E" could be correct, but  I suspect fashion drove the development of processes to create more vivid colors and colors on a repeatable consistent basis.  At some point in time case colors were accepted as a legitimate, decorative metal treatment.  Colors certainly appeared on carburized parts prior to this time period, but it seems they were not desired and were removed in some manner.   

[JCKelly]

Cyanide cases stay hard even when tempered because potassium cyanide (KCN) adds nitrogen (N) as well as carbon (C) to the case. The iron nitrides do not soften. I ran into this personally when as an Evil Young man I went to (shudder) reconvert an English lock on a Southern rifle. Drilling through that case, even locally tempered w torch, was interesting. Then I remembered that I was a metallurgist and . . . Duh  That Brit probably did not use cyanide, but leather charcoal does the same thing, puts some nitrogen in the case. Nitrides superior for wear resistance, a little more brittle than one gets from carbon alone.
As far as color hardening is concerned, the best (only?) published work on this is by Oscar L. Gaddy, Winter 1996 and Spring 1997, The Double Gun Journal The more durable colors come from calcium phosphate in the bone charcoal.

[The other DWS]

I was unclear in my wording on "E" so added a corrective.

[Jim Kibler]

Again, it is my belief that fashion drove case colors rather than technology. 

[The other DWS]

Jim, I agree that it appears that visible outer colors appear when it became marketable/fashionable to do so.  However would you not agree that that had to be able to be produced reliably and consistently on-demand before they could become fashionable?   

I can readily see some highly regarded sportsman, deciding, with his be-spoke gunmaker, that colors were cool and just the thing to blow his buddies/competitors away, thus starting the fashion.

It may be a chicken-and-egg kind of thing in terms of popular acceptance,  but they had to be able to do it, before it could become popular.

Has anyone ever seen or seen documentary evidence of an american-produced colored lock from the flint ear?

[Jim Kibler]

Well, colors sometimes appear without even trying and it's really not that difficult to make them happen on a consistent basis.  Lower carburizing temperatures and avoiding air contact prior to quench are the big ones. Pack make-up would have had an influence as well.  I guess my feeling is that since this stuff was done for a long time and the necessary steps to achieve colors are not that complicated, I don't think any huge technological breakthroughs were necessary to improve case color quality and consistency.  My views are that when it was desired, processes adapted and changed to meed the demand.   Over time it was refined and tweaked to produce better results.  This is just my guess on how it developed though.  It could have been more along the lines of what you have suggested.

[James Rogers]

Kind like hammer tracks in iron work and all the rough smith work you see today?
Thru centuries of the forging process, it could consistently and reliably be produced but it was not until there was a market for such that it was sent out of the shop that way.

[smart dog]

Has anyone ever seen or seen documentary evidence of an american-produced colored lock from the flint ear?

Hi,
Here is one example.  According to Hartzler and Whisker the US model 1816 musket produced at Harper's Ferry had case-hardened locks that retained mottled colors.  However, I doubt they did anything to purposefully enhance the colors.  The mottling was probably just a consequence of case-hardening the lock plates.

dave

[The other DWS]

Any idea if that was based on viewed examples or contract/mil. spec.

of course mil. spec is based on sturdy, cheap, reliable, cheap, built in my senatorial district.  so not paying a penny extra to polish off the colors would fit right in a US military scenario.
  I also vaguely recall seeing some well preserved US Martial pistols of that era or slightly later that had time faded colors.

[smart dog]

Hi DWS,
No I don't know if it was a specification or just an artifact of production.

dave

[Dphariss]

I think its necessary to point out that color case colors can be produced without hardening the surface at all.
Lots of Italian repros came this way at least back when I was buying and/or working on the stuff.

Dan

[Jim Kibler]

Here is the quote Dave mentioned. This is the same author who credits Bailes with the iron rib.
I would think that by 1800 case colors would have been in vogue and could have been coming on in the latter part of the 18th century although I would not think it was exclusively used across the board.

" The late Duke of Kingston, of Sporting memory, had a favorite gun, on this construction, made by Bailes; who, if I mistake not, was the inventor of the Iron Rib, first introduced blue mounting and springs, and left the tints produced by case-hardening on the lock. It is unnecessary to point out the beauty of these tints, or the facility with which the work is kept clean, from the pellicle which is most highly converted into steel, and hardest, being retained on the surface; but many of the workmen themselves, though for fashion sake they put the blue colour on their springs, are ignorant of the advantage arising from it; and that watch springs, after being hardened and tempered, by polishing lose their elasticity, which is restored by blueing. (See Home's Essay on iron and steel.)"

I find a few things interesting from this quote.  First, from a broad perspective, I can say that Bailes was not the first to introduce blue mountings and springs.  This is a treatment that goes back at least as far as the 17th century in French work.  Perhaps this broader perspective was not the one used by the author of this passage, however.  Second, he indicates that polishing springs results in their elasticity to be lost.  From a metallurgical standpoint, I see no reason to beleive this.  Any thoughts?

[James Rogers]

Jim, I cannot add anything technical to that observation but I have seen a trend in the period for writers to make a gunmaker bigger than life. Could be this writer was Bailes' Col. Hawker?  Would be harder to disprove if others in the period credited Bailes with these multiple "improvements" but this is the only source I am familiar with. Another thing to consider is the innovations and patent race that was going on. These factors could skew the real facts and muddy the waters.

[JCKelly]

One may case harden (case carburize) steel or wrought iron by packing in wood charcoal and heating to some red color for a period of time, then dump the whole thing into water.

Whether or not the surface actually gets hard depends upon whether the part was in the pack long enough to absorb any amount of carbon, and how hot it was heated. Color case hardening as described by Oscar Gaddy is done at a rather low temperature, for a very shallow case.

Colors. As has been stated, pack hardening in charcoal often gives some amount of colors. Depends on more variables than I know, but one is whether or not air can get to the parts before they hit the water.

Guys who did this centuries ago had the same industrial outlook we do today. That is, I want to get this surface hardening done with less expenditure of time in the furnace, or maybe a deeper case. To that end people added a wide variety of Stuff to the charcoal in hopes of speeding things up. One, already mentioned, was leather charcoal. This adds nitrogen, making a case harder and more wear resistant than just plain charcoal.

Another is to add bone charcoal. In addition to, hopefully, speeding things up the calcium phosphate can give wonderful colors. These colors are not the thin, easily removed temper colors that come from hardening in wood charcoal. I might speculate that the colors were regarded as secondary to improving the process, before people decided they were pretty & went about developing the Art of getting good colors.

Back to speeding up the process. Rene Antoine Ferchault de Reaumur studied how to develop a reliable process for "cementing" (deep pack-hardening) iron. He found that sea salt and sal ammoniac both gave good results (I'll bet they ate the $#*! out of his pack container, whatever it may have been). While I cannot locate the reference this evening, I recall that pigeon dung and sea salt were a good combination, added to the charcoal. Salt was a popular additive to charcoal for case-hardening, it sure didn't give colors but it, well, cleaned up the iron surface so that it more readily absorbed carbon.

In the 20th century when pack hardening was still an industrial practice the chemical barium carbonate was added to charcoal to speed up the process. Not very poetic but it worked.

Here is a nice 1532 A.D. recipe for hardening files. Perhaps not cost-effective today but it would make a fine file:
The Temper of Iron for Files

 It must be made of the best Steel, and excellently tempered, that it may polish, and fit other iron as it should be: Take Ox hoofs, and put them into an Oven to dry, that they may be powdered fine: mingle well one part of this with as much common Salt, beaten Glas, and Chimney-soot, and beat them together, and lay them up for  your use in a wooden Vessel hanging in the Smoak; for the Salt will melt with any moisture of the place or Air. The powder being prepared, make your iron like to a file: then cut it checquerwise, and crossways, with a sharp edged tool: having made the Iron tender and soft, as I said, then make an Iron chest to lay up your files in, and put them into it, strewing on the powders by course, that they may be covered all over: then put on the cover, and lute well the chinks with clay and straw, that the smoak of the powder may not breath out; and then lay a heap of burning coals all over it, that it may be red-hot about an hour: when you think the powder to be burnt and consumed, take the chest out from the coals with Iron pinchers, and plunge the files into very cold water, and so they will become extream hard. This is the usual temper for files; for we fear not if the files should be wrested by cold waters. But I shall teach you to temper  them excellently

G. B. Della Porta, 1589, Sources for the History of the Science of Steel 1532—1786,  Ed. Cyril Stanley Smith 

Soot added the carbon, Ox-hooves nitrogen as well as carbon. Melted glass + salt cleaned up, or fluxed, the iron surface so that it was quite receptive to reacting with carbon (really, with the carbon monoxide which broke down to carbon + carbon dioxide on the surface)  Enjoy.

[smart dog]

Hi Jim,
You raise good questions that apply to many of these early writings and references.  I did a quick google search for Sir Thomas Frankland 6th baronet.  He was a botanist and member of the Royal Society so he probably was a good observer and an experienced outdoorsman but unlikely to have much direct experience with metalurgy or gunmaking.  In my years working as a research biologist, I've listened to people describe natural history or ecological events that they witnessed.  I find that people often are pretty good observers of things when their interest is peaked, but they often fail to correctly interpret those events.  In Frankland's case, his comment that Bailes left color tints on his locks is likely accurate because it is a straight forward and easily remembered feature without need for interpretation.  His comments about the bluing of springs and the effect on elasticity is an interpretation that he probably was unqualified to make and I give it little credence.

dave   

[Jim Kibler]

Makes sense to me, Dave.  I don't doubt his comments regarding case colors, but am still perplexed as to the lack of 18th century examples.  You have probably looked at a good number of later 18th century examples.  Have you encountered any with remaining case colors?

Jim

[The other DWS]

part of the problem might be a natural fading with time unless arms are very well cared for.  I wonder if arms kept cased might not hold their colors better than ones stored in the open  (unless your servants were overpolishing them )

   I have a lot more exposure to the cartridge singles shots of the 1880-1920 era due to my participation in ASSRA matches.  Color cased actions were very very common, more common than not over the whole time span.  I do not know whether they were done with the bone-charcoal process or with the cyanide process.  one type may be more durable and fade resistant than another,  I don't know.  but it sure seems like the rifles that were built as high grade target rifles (and probably received much better care as a result) have retained their colors much better than run of the mill hunting rifles even if made in the same serial number range. It appears like many of the target rifles were kept in cases when not in use. I don't know if light exposure impacts case color fading or not.   I'll ask about this on the ASSRA gunsmithing forum.

[Dphariss]

part of the problem might be a natural fading with time unless arms are very well cared for.  I wonder if arms kept cased might not hold their colors better than ones stored in the open  (unless your servants were overpolishing them )

   I have a lot more exposure to the cartridge singles shots of the 1880-1920 era due to my participation in ASSRA matches.  Color cased actions were very very common, more common than not over the whole time span.  I do not know whether they were done with the bone-charcoal process or with the cyanide process.  one type may be more durable and fade resistant than another,  I don't know.  but it sure seems like the rifles that were built as high grade target rifles (and probably received much better care as a result) have retained their colors much better than run of the mill hunting rifles even if made in the same serial number range. It appears like many of the target rifles were kept in cases when not in use. I don't know if light exposure impacts case color fading or not.   I'll ask about this on the ASSRA gunsmithing forum.

Stevens colors is classic Cyanide. Look at the standard Shiloh of today they look like Stevens colors. All Shiloh's until recently were cyanide. Now its possible to order charcoal colors.
For Cyanide process when I worked there parts were placed in the pot for a specific time, set out in a rack to air cool. More parts were then cycled through and the first batch then put back in, brought to temp, soaked,  lifted out and then quenched. Exposure to air is not a factor. It is a very different process than charcoal, less labor intensive and more fool proof I believe.

Small parts were done in baskets. Actions etc hung on racks.
What they do today I could not say. But in doing large batches quench water heated by previous parts could effect hardness.

Colors will fade in sunlight or so I am told.

Dan

[smart dog]

Hi Jim,
Most English guns that I handled and examined closely were 19th century pieces.  I've only had half a dozen or so 18th century English sporting guns in my hands.  I've looked at many more military guns from that period and I've seen more sporting guns behind glass.  I don't recall seeing any color from case hardening on the locks although I never really paid much attention to that detail.  We need Keith Neal to come back and tell us what he observed. 

dave     

[James Rogers]

We need Keith Neal to come back and tell us what he observed. 

dave     

Absolutely!
And he would probably also like to see what has been found to counter some things he wrote about.

[The other DWS]

Just  A ColorCase reference FYI:

  I have just been referred to one gentleman's pursuit of CC methods and practices as executed by the Marlin firearms company.  It deals with a later style of colors I am sure, but the discussion on the Marlin Collectors website runs on for a whole bunch of pages.  I read the first page and will probably wade through the rest over the next few days before I go back on the road just to broaden me limited knowledge base.   I'm listing it here just for reference on the topic

www.marlin-collectors.com/forum/viewtopic.php?f=21&t=3732

[44-henry]

The guy on the Marlin thread is looking for colors, and he gets them. The problem is that he generally quenched at about 1200 degrees which in my opinion is way too low. If you follow his thread you will see that he avoids higher temperature quenches partly to reduce the risk of warpage, but also for enhanced colors. You can get very good colors if you quench below the critical temperature, but it is certainly not ideal if you actually want to harden your parts.

[Dphariss]

Another thing he does not discuss on the Marlin site is DEPTH of case.
 There is more than color and "its hard" involved.
Dan

[The other DWS]

I think he was just trying to find out marlin did their colors and trying to duplicate the process to do restorations.


Dan,  IS there any diff between bone charcoal and cyanide-added processes in terms durability, depth of harness, and fade resistance?

[Dphariss]

I think he was just trying to find out marlin did their colors and trying to duplicate the process to do restorations.


Dan,  IS there any diff between bone charcoal and cyanide-added processes in terms durability, depth of harness, and fade resistance?

I am not sure about all the factors in "hard" but a case hardened part is a case hardened part. As to depth of case I think that cyanide is faster than charcoal since the parts are put in a hot pot rather than having to pack a container and heat is all up to temp.  Cyanide will not give the right colors for most 19th century guns but it will produce more parts per day with less equipment and fewer people  than a similar level of production with charcoal will. As previously states its more fool proof.
So far as I know the colors are all very thin and are not "hard" they are just an oxide on the metals surface. It is all to easy to damage or remove colors made by either process. But a soft scraper, for example, will not damage the colors when stocking a hardened action if reasonable care is used. When necessary I could shape to a hardened action with a soft spring temper  scraper. Then remove the metal from the wood for sanding.
Case depths over .005-006" are not needed but I need to have a conversation with an expert to get the final word on this. I am pretty sure that the low temp casehardening is not going to produce as good a case as higher temps will especially so far as  depth of case.

Dan