doublegunshop.com - home Forums Thread Like Summary - British Case Coloring

I was able to recover this PDF from "Guncraft" in 2015. You will need to cut and paste the link
https://web.archive.org/web/20151010095002/http://www.doubleguncraft.com/uploads/PDFs/GunCraft_Book.pdf

Gentlemen;

Here are some things that I saw in Robin's video.

The parts are de-greased via ultrasonic cleaner and then some of them are wired together with copper wire--this to me shows that his max temp is well away from 1984 degrees F for copper melting and I will comment on this later in this list of things I saw. Robin is not overly concerned with touching the just cleaned parts with his bare hands and his hands seem clean. Robin also did not place any additional steel supports wired to the side locks to prevent warping as some American color case hardeners are known to have done--another indicator of the control of max temp by Robin to my mind.

Robin carefully and strategically keeps the parts separated and I suspect they are placed in a pattern that he has developed from experience.

Robin surrounds the packed parts in the crucible with the charcoal and bone mix and it seems to me that the first part packed (the action) must have had about 2 inches of this mix to rest upon when Robin placed it in the crucible. The charcoal/bone mix is coarse as mentioned I would say that the mix is about 70/30 charcoal to bone and the bone looks very clean indicating that either Robin or someone else "burned" away all the animal flesh before it was mixed with the charcoal. As to the mix there is complete absence of fines as you see none when Robin dropped some of the mix on the floor. I think it is important to note that Robin placed 3-4 inches of mix on top of all the parts, then compacted it by tapping on the crucible and then before he placed the cover on the crucible he added more mix to completely fill the crucible--you have to look close to see that the crucible was filled to top. He wisely made the top 1 inch short so that he could place his tongs into the crucible to remove the top when he was taking the hot crucible to the water tank. This cover is very loosely fitted. The "shaking" and tapping down of the mix in the crucible gives Robin the proper mix surround of the parts that he desires as well, I suspect.

This filling of the crucible completely, the 3-4 inches of charcoal/bone mix cover over all the parts, and how Robin flipped the crucible over into the water tank, kept the ambient air contact with the parts to a bare minimum.

The tongs that Robin has with nearly 4 foot long handles are built for purpose and give him great leverage in holding the crucible as well as distance from the water splash and thermal reaction and allow him the leverage also for his final flip into the water quench.

I spent a couple of decades of my early life in a forging/blacksmith shop and learned how to judge temperature by color and the max temperature that Robin heated the crucible is of interest and important to my mind. You will note that he has a gas-fired furnace and there are no temperature gauges seen or any cable emerging from the furnace to indicate any remote temp devices. Therefore I think that Robin judges the temp by eye and the temp appeared to me to about 1500 degrees F when he opened the furnace door. And he lets the crucible heat for a time that he has learned in his years and from his mentor when he was a young man---I believe it was Billy Woodward.

As mentioned the water barrel has been air infused somewhat, but no continual air flow as some American hardeners advocate, and it is just local water and at whatever temp it is. However, the way that Robin holds the tongs and flips the crucible dumping the parts into the water quench is very important--he lowers the crucible into the water for a short distance as he flips pouring all the contents into the water so that there is the barest minimum contact with any ambient air. You will also have to look closely to see the front of the crucible enter the water during the flip.

In the video Robin shows that there is not warping of the side locks fitting into the action body. I believe his control of the max temp of the crucible and its contents of course is key to the warp control. Of course there is bound to be some minor warping such as with the triggers that will have to be relieved.

As a side note, after Robin made this film some time ago I wrote him an email and thanked him for doing the video for us amateurs and he wrote back saying that it was great fun for him to show the process. We are thankful for craftsmen like Robin who are kind to show us things that are not shown by others in the gun trade.

Douglas Tate in www.thefield.co.uk
http://www.aabrownandsons.com/assets/files/FieldCH.pdf

A very interesting thread and subsequent discussion. Here is an example of what original case colours look like re: a circa 1920/1925, Clabrough & Johnstone, SLNE shotgun. Not too bad an effort for just a Colonial export trade gun.





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TC

Robin Brown color case hardening video, click and scroll down to see it.

https://www.aabrownandsons.com/videos.html

It all looks so simple though it is one of the best kept trade secret process. Just look how vibrant the colours are especially the blues and yellows are. just take a look at the colours of re case hardened guns look on your side of the pond using same process. In the AA Brown video it is all there but missing a few important pieces of information.

I'll take a swing at this. The sieve size seems to be quite course, and certainly the raw material sources would be different, but the charcoal in the video might be prepped a bit different than what we might see typically in the US. There was relatively little burn down of the char level after the heat cycle.

Posted for bushveld, his 20 bore Double rifle with colors by Turnbull. More info on it in his post above.

the claybrough cc images above are reminiscent of the cc produced by the late, great tony treadwell... images of which may be found in his fine, now scarce book on engish gun restoration...

https://www.lulu.com/shop/tony-trea...duct-1ggvkn8v.html?page=1&pageSize=4

This is pure speculation, but there may be a PID, thermometer, on this oven. At the lid removal, there is a brief glance at a small gauge electric wire coming out of the top, a bit to the right. It would be too light to power a blower, but it appears the heat source comes in from the bottom anyway? Definitely, I do not dispute judging temp through experience, the crucible though seems to hover in the lower red, medium red spectrum? The crucible never seems really bright to my eye, the way part of the oven interior appear.

The thing that always is interesting to me is the delay from oven removal to quench, either counted off or part of the circumstance of walking the crucible out of the shop. I think there is a cut in the video, but it appears to be a continuous process that likely takes fifteen to twenty seconds from the oven to the quench. Particularly with the lid off, the parts are likely cooler than whatever temp they soaked at, in the oven. I have always wonderered if that was one of the tricks to low distortion, quenching games to catch the parts cooler than the nonmagnetic point on the way up? An edge to center of mass temp difference might also help with his color distribution control, ending up with those classic islands of blue framed by paler colors.

I couldn't open the pictures, but the Venters book mentioned early on in this thread, and the AA Brown excerpt from that book, elaborates a bit. The video shows a sample of one, but Brown explains how he believes proper British case colors has an area of blue in the center of a part, more or less framed by the other nonblue colors.

If you go to Drew’s first post in the thread, and copy the link to Vic Venter’s book Gun Craft, on pages 92 & 94 there is an inset called “Colors on Brown Guns”. The author describes what Craigd was alluding to. It states that each hardener has their own signature style involving various techniques (secrets of the trade, jigs, fixtures, etc.) that he uses to achieve consistency of colour and pattern. Robin Brown’s colour case hardening technique involves how he packs the crucible container and positions the various components within the carbon pack in-order to achieve his desired colours, pattern and placement.

TC

Yes, please elaborate. I have never seen any suggestions, recipes, or techniques for getting a high percentage of blue colors during case hardening.

I've noted that high condition Syracuse Lefevers have a much higher percentage of blues and purple-blues than most makers. Many are predominately blue over the sideplates with only a bit of ghosting around screw holes or the edges. When I see a Lefever with a lot of mottled colors, I immediately start to look for other signs that it has been refinished.

There is a huge difference between refinishing and restoration. And very few so-called "restorations" on Lefevers have anything approaching the period correct case hardening colors. I have the name of one case hardening gunsmith who seems to be able to consistently pull it off in a convincing manner. Most cannot.

Here's a DS Grade Lefever that illustrates what I'm saying even though it has seen a fair amount of use.