doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Sunlight and case colors

The sage of modern day case hardening, Oscar Gaddy, wrote a series of two articles long ago that were published in the DGJ. I have them both and have read them many times. One of the things I remember most vividly is the electron microscope pictures of the surface of a color case-hardened surface.

That picture shows physical irregularities that are in the shape of tiny prisms which refract light in ways that cause the human eyes to see various colors.

I can completely understand how physical wear can affect those tiny prisms and cause them to not refract light the way they did when new, thusly affecting the colors we see. But, I have yet to be able to understand how sunlight could reshape those tiny prisms. We are told regularly that direct sunlight can do this, and that we should keep color case-hardened guns out of direct sunlight as much as possible. I even practice this myself, just to be safe.

My question is this ........ what PROOF exists that sunlight can do this? And, if proof actually exists, has it ever been explained how that happens?

There is no proof. It does not happen.

I had a 16 gauge Charlin re-case colored by Doug Turnbull. At that time Doug told me that case colors were oxides of organic compounds and subject to fading in sunlight.

I had no reason to doubt him, and didn’t ask for any proof.

I sold the gun to a friend, a serious sliding breech collector, who has kept the gun in a safe since the day he got it, maybe 25 years ago. I was startled how nice the colors still looked when I helped him move the safe to a different part of his house.

I have no proof, just what the guy who does if for a living told me, and what I have seen.

Best,
Ted

Sunlight can provide the energy to form iron oxides. If oxides form on a case colored surface, that were not there before, it is reasonable to expect, that surface will reflect light differently.

How can that happen, Craig? I can understand oxygen, moisture, and heat accelerating the oxide forming process. But, how can merely sunlight do it? I need to understand the process if I am to accept it. Not saying I can't. Just saying I do not have the information needed to do so at this time.

I am the original skeptic .......... sorry.

Stan, a while back I was curious about this subject and went down the internet rabbit hole looking for the same answers you are.

I found dozens of claims that sunlight degrades case hardening colors over time. And I also found many people saying that sunlight has no effect whatsoever. However, I found no credible tests to determine if the claims of fading due to sunlight have any basis in fact. Naturally, I checked Doug Turnbull's website to see if he had any insights, and he didn't address it there. So it was interesting to see Ted say Turnbull does have an opinion. I did find some guys who claim they do bone charcoal case hardening that did say sunlight may fade the colors over time, but none of them showed any proof. I'm not sure how valid testing could be done since samples exposed to weather would oxidize, and window glass filters out a lot of UV light.

Since then, I concluded that this claim is probably just another myth that became accepted as fact after being repeated so many times... something like the myths that all Damascus barrels are dangerous to shoot, shiny bores on vintage shotguns means probable honing, or that small bore Ithaca Flues frames are especially prone to cracking.

On the other hand, if the colors we see are at least partially the product of the formation of some iron oxides frozen during the quench into the top couple thousandths of the surface, I could maybe accept that prolonged exposure to very direct sunlight might have at least a minor effect on those colors over time. I say that only because we know that metallic oxides have long been used as pigments for oil paints, stains, and dyes for cloth. All of those things do seem to be subject to fading from sunlight. However, they are not part of the crystalline molecular structure of the surfaces they are applied to as case hardening colors are. For that reason, I have never worried about using my guns with strong case colors on sunny days, and have never worried that I should be covering them with lacquer or anything but the same gun oils I use to protect the blue on my barrels. I avoid wax on case colors because many waxes contain mild abrasives. And I've also assumed that the old guns I have with faded or nearly non-existent case colors got that way because previous owners just didn't care for them properly. I'd be much more concerned about not cleaning and oiling my guns after exposure to rain, snow, perspiration, or even handling case colored surfaces with leather gloves impregnated with abrasive dust or tanning chemicals.

Stan, my point of view is that assumptons have to be made, such as, in open air where sunlight is available, it is reasonable to believe that oxygen and water in the form of humidity, are also available. The quote above, strips it down even further to exclude firearms case coloring?

Anecdotally, some folks try to retain "patina", which may be at least in part due to oxide formation, because it looks, reflects light, differently than a new finish? Sometimes, one might look under a stock or other part for a closer look at how original colors might have looked? Is every external case colored gun surface subject to "pyramid" wear, maybe?

I also choose the term reflect, over refract, regardless, some skepticism is healthy, but absolutes such as in the quote, have the backing of proof?

I remember Dr. Gaddy discussing a test he did. He made two rectangular pieces of steel, then color case hardened them. He put one piece in a window sill and the other in a drawer or similar. After an extended period of time, he put them side by side. There was no difference in color.

I remember the same. This was pretty much the definitive answer.

Craig, yes, but to my way of thinking oxygen and humidity (moisture/water) can also present in the absence of sunlight, can they not? And, oxidation can and does happen in the dark, if oxygen and water are present. So, what does the sunlight add?

To wit, even though a forend iron has been devoid of nearly all light, under the barrels, and sustains high levels of case color, it was never deprived of oxygen and moisture, except ............. by a light coating of rust preventative oil. Had the oil not been present as a moisture barrier the oxides would have formed anyway, without light.

So, back to square one for me; what exactly is it that sunlight itself can do to the surface of case colored steel that can transform the prismatic surfaces?

Thanks, Daryl. I did not remember that. If it satisfied Dr. Gaddy I'm comfortable with that, too. Amazing though, how old wives' tales can persist.

No arguement from me Stan, just opinion. I'm plenty satisfied that there are different types of oxidation, the most obvious, being pulling out somethng that's been in the back of a dark drawer, that has rust on it. As a protectant, not lubricant, oil has the role of resisting the formation of the wrong type of oxides? I'll go with Dr Gaddy on this, but at the same time, a remaining question is, why aren't original colors, common place. Extended period of time? Some of us might have an example or two of acquiring something that was ninety years old, and is now fifty percent older. Whatever causes patina, seems to be a slow process?

Again, I'll go with Dr Gaddy on this, but visual changes due to oxidation affect most things around us. How does this one process, without strict controls, escape untouched? I have no skin in the game to perpetuate wives' tales. If I am not mistaken, the science says a steel/iron surface needs to have a hundred percent coverage of certain oxides, to be able to resist the formation of additional oxides.

I discussed Dr. Gaddy's experiment with sunlight and color case hardening colors above. That was his experience with his method of color case hardening. One must realize that there must be many variations to the methods of color case hardening and the steels used.

My interest over the years has often been with shotguns by Baker Gun and Forging Company. Their method of color case hardening in later years produced very pretty colors of robin's egg blue etc. Sometimes when these case colors are worn or faded, the underlying metal looks to almost be plated , maybe like a nickel or almost chrome shine. I am assuming that this shine came from the polish given prior to coloring.

After Baker Gun and Forging Company sold the gun making business to H D Folsom in 1919, a different process was used in color case hardening Baker marked guns. This process had darker colors and seems to have been more durable colors than most other guns of the time. It is not uncommon to see examples of these guns with still vibrant colors, although the rest of the guns show wear. I do not know what process they used, but it was extremely durable.

Lefever Arms [non Ithaca] consistently used a method resulting in very pretty color case hardening. Guns showing wear often have better remaining colors on the sideplates than on the gun frames. I am assuming that this was caused by a different composition steel being used on the sideplates than on the frames.

As always your expertise is appreciated Daryl

This is the highest case color Baker image I have; a c. 1910 R grade





Some Smiths had a bit of 'mud' behind the colors



Hunter Arms Fulton

I suspect that the loss of case colors over time is a combination of several things. Surface contact with skin and gloves, oxidation of the surface caused by humidity, moisture and the various air pollutants we all get exposed to (automobile exhaust, stack emissions, volatile organics, etc.), & contact of a said surface with "life in general" (the baize in a gun case, the lining of a gun slip, the material on a car seat, etc.)

My little Dickenson Estate .410/28 had vivid case colors when I first got it (shockingly so! Way better than what I expected for what I paid) but... with use over the accumulating years (7-8?) it has noticeably faded. The colors are still present but they aren't nearly as vivid as they once were (I suspect that there may be even a natural "fading" process going on here as well). I suppose I could have prevented that by never using it but....why the hell not? It was a relatively inexpensive Turkish gun that I bought to use and learn about. To not use it completely defeats the purpose of having it. Does sunlight take it's toll? I would suspect that it does (clothing set into a display in the front of a store fades over time like you would not believe), along with all of the other "weathering" components of life. Automotive finishes have been engineered over generations to resist such "weathering" forces. I suspect that a traipse through the chemistry of automotive paints and coatings would give one a start into understanding how such things really happen. Sunlight is a very powerful force in this world, so I wouldn't dismiss it out-of-hand because of an anecdotal experiment that Dr. Gaddy performed on one occasion and over a limited period of time. That's not a knock on Oscar Gaddy (as I'm a big fan of his work) but I suspect that he was occupied with bigger things.

It would be useful to understand what the "primary forces" were in the loss of these wonderful gun finishes over time so one could take the necessary steps to reduce or prevent it. Coating the case-hardened surfaces in a protective finish seems to be somewhat effective (otherwise gunmakers over the years wouldn't have gone to the time & trouble). There seems to be lots of room for additional growth & understanding here, so who's going to be the next "Dr. Gaddy"?

I remember all the discussions about case coloring and one person on here said that he had a gun that sat in the corner of a room where the sun shone one it. And the sun removed the case coloring on the side of gun where the sun shined on it. I remember one person who kept insisting that the sun faded case coloring. (But I won't say who it is). Picture it this way: If a rusty nail sits out in the sun, will the sun remove the rust from it? The answer is no. It won't removed case coloring either.

About $69K separates the purchase price of these two guns (can you imagine that? I struggle with it). This circa 2017 20-bore Westley droplock only goes out in very controlled conditions (my buddy even carries a protective slip in the event it rains). I am hoping that Westly Richards has taken into account the need to protect the finishes on this gun, but I'm not holding my breath.

A shockingly beautiful gun, but with zero utility IMHO. It does not strike me that the owner enjoys the reality of it's possession. It seldom sees the light of day and he has taken to not mentioning it in conversation.

12 pages here
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=326247&page=all

Colt forum claim that Turnbull clear coats his case coloring
https://www.coltforum.com/threads/c...d=3089415&nested_view=1#post-3089415

Mike Hunter likely has an opinion
https://mikehunterrestorations.com/restorations.html

There is no question Turnbull clear coats. The work he did for me was coated. It further warms the colors as well as protects them. Classic Guns in IL also did this and perhaps Wyoming Armory (I may ne miss remembering on that one. ). All of them would leave it off on request

Isn't this basic physics? The surface is getting bombarded by photons which puts the molecules in a higher energy state which is not stable in the presence of some other compound (air, water, oil, whatever). Some degradation must happen. Maybe it just takes a really long time.

Lloyd, I can't equivocate clothes' colors fading in sunlight with case-hardened colors fading. One's colored with dye. The other is not colored with anything. The colors we see on the gun is a prismatic effect. For sunlight to change what the eyes see, on a case-hardened surface, the photon bombardment Ryan speaks of would have to physically change the structural shape of the tiny prisms.

Can that occur? IDK. Basic physics never taught ME that. Heck, as old as I am I'm not even certain photons had been discovered when I last sat through a physics class. 🤣

Stan: what I got out of the wondeful list of old posts here that Dr. Drew provided (wish I could search that effectively here) was that the destructive component of natural light here (i.e. sunlight) was UV. Ultraviolet light is a known force in many processes now (and has been for most of my lifetime). How it exactly diminishes the beauty of bone-charcoal hardened finishes over time still excapes me however.

If it is truly the UV rays in sunlight that can degenerate case colors there could be an easy fix. Automotive clear coat protects paint from the UV rays, and is almost perfectly clear. Yet, I believe there are solvents that will remove it if need be.

However, before I try some I've got to be convinced that this even happens.

Something changes it. Roughly 6-years after purchase this was what my case colors looked like on that Estate BLE...



Now, it wasn't protected in any way that I could tell (no protective coatings, and I wouldn't have expected that on an inexpensive gun) and I didn't expect the colors to not change (old guns look that way for a reason, right?).



Significant change, eh? Now, you can see where I had been carrying the gun on the later picture but it wasn't just me using it that caused such a departure from it's original appearance. It's either a natural degrading of the finish over time or it's caused by environmental issues, or it's both. I certainly didn't abuse it, but neither did I baby it. I merely used it for it's intended purpose.

This happened pretty quickly too (6-years is nothing when you think about it) and I have always stored it nicely cleaned (well, wiped down with a light oil) and upright in my gun cabinet, well away from any real source of UV. Go figure?

Interesting discussion, thought I might share an experience I have had. For the last 27 years I have hosted The Oregon Gunmakers Fair at my shop every spring. The emphasis of the Fair is a number of short seminars on traditional gun making techniques, predominantly centered around the building of flintlock and percussion firearms. Some 20 years ago we invited a professional metallurgist to demonstrate case color hardening. He used 1 1/2” square coupons of mild steel for the demo, and produced some wonderful colors, with attendant hardness. One of those example pieces has resided in a south facing window all this time, with no degradation of color, and no, it has had no coating applied. A sample of one, I know, but I suspect wear is a greater contributor to loss of color.

OTOH, my Dickinson is about 1-2 years older than yours and I cannot tell that the colors have degraded in the least.

Thanks for that information, Warren.

The plot thickens.

Yes it's a know fact the sun bleaches everything on earth but case colors on guns.

This is an interesting topic, and I'm still in agreement with Stan. We simply don't know if sunlight alone can degrade case colors.

As I said earlier, I did a lot of searching and found exactly zero definitive tests done to determine the effect of sunlight. The very limited and informal test supposedly done by Dr. Gaddy would hardly constitute "good science", so it should not be accepted as Gospel by those who demand "good science" in matters of Climate Change, lead poisoning, declining quail populations, etc.

It only involved one small sample. We don't know if the samples had any protective coating such as lacquer, wax, or gun oil. The alleged sample was done with sunlight coming through a window, and we know window glass filters out a lot of the UV spectrum, especially UVB. Nobody hunts under glass or in a greenhouse. And we also know sunlight is composed of a wide spectrum of visible and invisible wavelengths, so there could be something aside from UV alone that MIGHT cause a change.

It involved only one case hardening process and one alloy of steel. So we can't say that different compositions of charcoal, different alloys, or different quenches create the same changes to the molecular structure of steel which we see as case colors. Should such a test be done in an inert gas atmosphere to exclude the effects of air or pollutants? We don't even know how much time was involved in this "test". We would also have to include the degree of surface polishing because we know that highly polished steel resists oxidation better than a rougher surface. The case hardening process is far different than dying cloth or painting a car. Stan is correct when he says that case hardening is not simply adding a pigment or dye to the steel. However, we do know that cooking steel in a crucible with different recipes of bone and wood charcoal for hours at high temperatures does in fact infuse carbon, carbon monoxide, and other compounds a few thousandths of an inch deep into the surface of the steel. This chemically changes the steel near the surface by giving it a higher carbon content than the base metal. But is it just carbon alone, when we know that different charcoal contains many other elements? The quench somehow locks things in place, and the quench itself is often done with different water at different temperatures. This is what somehow creates those "prisms" Stan spoke of, which reflects and refracts light to our eyes in differing hues and colors. So now we get into a realm of molecular and atomic bonds that are difficult to see or understand even with the use of electron microscopes. The quench may be straight rain water, city water, or it may contain additives like potassium nitrate, bat urine, or eye-of-newt. It may be agitated or infused with air bubbles. Most practitioners of the art seem to find that colors are more vibrant if they can exclude as much atmospheric oxygen as possible from the parts while dumping them into the quench. The guys who do great case hardening seem to eventually settle on a process that gives them good results, often through much trial and error. But if they know every detail of the chemistry involved, they certainly aren't sharing that knowledge.

If this thread accomplishes anything, I hope it begins to make people understand that conjecture, thinking, and even wild-assed guessing is OK... so long as it isn't stated as fact. Because as things stand right now, when you do a deep dive into this subject, you will find that books, magazine articles, and the internet is literally filled with so-called experts who state things about case hardening as fact, in their attempt to explain what causes case colors to fade over time. And most of what they are saying has absolutely no basis in proven facts.

So, you believe that sunlight bleaches case colors, like Clorox bleaches dye?

Stan,
Since case colors are the product of a reaction between steel, carbon, and heat, and no two lots of steel, bone or charcoal would be absolutely identical, nor would two quench solutions be absolutely identical, how can we assume wear rates or susceptibility to fade would be identical between different guns from different manufactures at different periods of time?

I read an article that made the point that Baker case colors were considered very durable in the era they were produced.

I have often wondered who came up with that, and how?

Best,
Ted

Never known the sun to bleach a stone. A flint chip today looks about like it did 10,000 ago when someone used it for a knife. Minerals don't bleach easily or often.

Flint is grey photo degradation affect red purple blue first

Ever seen an agate fade? Petrified wood? I think there are lots of things on earth that don't fade. Lots of them are minerals and so are case colors.

Bakers have more "durable" colors because their owners would rather hunt with their Parkers and Elsies and Foxes instead. So the Bakers stay home and don't see the wear.

Acids and abrasion are the two things that "fade" case colors. I've never tested gun oils for pH, but I would wager than a few of them are on the acidic side slightly. If so, that would do the job over time, just like the oils and sweat on your hands may do the same thing. Grit is pretty obviously a factor since the high spots fade first.

I think there are more questions than answers for why case colors degrade. Ever notice that the levers on Savage 99’s often still have strong color, when the rest of the gun shows considerable wear? Base metal, hardening process, I really don’t know?

Does a 99 balance at the receiver?

The sun will cause anything to fade eventually

We will have to agree to disagree.

Are cyanide chemical case colors similar to bone charcoal colors at the microscopic level? It would be fascinating to see both types of colors at a microscopic level.

Never forget that the Sun is flat. (And also fairly thin. Forces unknown to us might be able to bend it so it acts as a parabolic hotdog-toasting reflector and fades the spines of our books around corners and whatnot. I've applied for an arts-council grant to study this.)

A 99 does balance at the receiver, which generally shows considerable bluing loss from carry. So, no doubt the lever gets handled far less. I own 3, one from the 30’s, one 40’s, and 60’s. These have all been well used in our wet climate in western Oregon, and still show good colors on the lever. If there are tough case colors, perhaps these have them?

Well holy crap I agree with you that it would be a fascinating comparison .

Don't worry. You will get over it...

So, a 69K gun and somebody has their big sweaty mitt all over the case colors. O-o-o-o-kay! LOL Just kidding, of course.

Does the sun bleach snow? Or water???... how about water? Is water deep in a cave lighter in color than water under a tropical sun?

Oh, of course... snow and water have no pigment. So let's consider some things that do have pigment, like rocks. I notice that most rocks don't get bleached by the sun, or are typically darker on the inside if you break them. After millions of years of exposure to sunlight, shouldn't all rocks on the surface be bleached white by now? Same goes for sand, which will be the same color a foot deep as sand on the surface exposed to the sun.

How about grass? Does grass turn a lighter green or get bleached out when exposed to the sun, or when it is deprived of sunlight?

And does the sun bleach skin, or does it make skin turn brown? Shouldn't Nordic people be much darker than indigenous Equitorial African people? Ever seen a black person with a tan line after exposure to the sun? I have.


Even on the moon, there are both light and dark colored rocks and dust, whether on the always illuminated near side, or on the perpetually shaded dark side. Clearly, there is more involved in color retention than simply exposure to sunlight.

But to kinda get back on topic, it seems the jury is still out on sunlight damaging case colors, and nobody has done any definitive testing to prove what is often stated as fact. It appears that there are a lot of other things that cause them to wear, fade, or become obscured. I'm still blown away by some of the results we've seen here that restore a lot of case colors by simply cleaning in an ultrasonic tank. That process probably deserves more study too. A couple days ago, I watched a YouTube video where a guy tested 8 different ultrasonic cleaning solutions by individually cleaning the filthy carbon crusted pistons and rods from an old V-8 engine. There was a wide range of results from the same ultrasonic tank, ran for identical times. Surprisingly, one of the very best performers was Cascade dishwasher pods, and the cost per gallon of solution was much cheaper than several of the more highly touted specialty brands. So the same could hold true for ultrasonic cleaning of case colored gun parts too.

I don't know if Doc Gaddy would say that case colors are are minerals. Most of us would conclude that abrasives can remove gun finishes, but why are the "low" spots fading.

I'm not sure what to call those colors other than mineral. It may not be the best name, but it is all I can think of. In the end, there are chemical compounds that are responsible for the colors. I don't think they are anything organic, though they may have had some organic origins at one time. Google tells me that the Oxford dictionary defines mineral as,

noun
1.
a solid inorganic substance of natural occurrence.
"it identifies the mineral or compound present"
2.
BRITISH
(in commercial use) effervescent soft drinks.
adjective
of or denoting a mineral.
"mineral ingredients such as zinc oxide"

So "mineral" seems appropriate to me. What else could we call them?


The low spots fade from anything acid. You know, of course, what would happen if you wiped down your guns with vinegar. If there is acid in your sweat or the oils in your hands, or possibly some gun care products are slightly acidic, they could be slowly fading your colors as well as abrasion. Things that are just very mildly acidic would take longer to do this of course, but it would still happen.

This is the same dispute that people had on here several years ago. As I previously said, think of case coloring as a rusty nail outside 24 hours a day. Would the sun, remove the rust from the nail? No. That was the way Oscar Gaddy explained it to us. I have to believe him. He was an expert. Good luck.

My point of view in the discussion is that the colors are oxides, and not likely zinc oxides. Iron oxides are not likely to be chemical compounds, but rather chemical reactions. The "discussion" seems to be, can sunlight provide the energy to drive the chemical reaction, to create new oxides on case colored gun surfaces, which results in a different visual appearance.

Earlier, there did not seem to be dispute that hidden, internal gun surfaces, may very well be protected by various traditional and modern oils, probably for corrosion and wear resistance. But, that is a general area of many guns, where case colors do not seem to be affected, or as affected by the appearance of fading.

craig, I think we are haggling over semantics then. Iron oxides would be minerals in anyone else's book and most definitely they are chemical compounds. How can they NOT be chemical compounds? Everything that physically exists is a chemical compound. They are not reactions. They are created by reactions.

But be that as it may, I don't think sunlight fades them. I see no evidence that it does and anyone that does the case colors in the windows test seems to find the same result - no fade.

Do you think sunlight will fade a rust blued barrel? That is another iron oxide.

Thanks Brent, I agree there is a disconnect, my mistake. I was thinking back to Gaddy's paper, and what I perceived, reference to things like petrified wood, as confusing.