doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com British Case Coloring

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.

Craig;

Like you I am uncertain about the electric wire.

Your thoughts about the non-magnetic point on the way up and down brought to my mind a "color" non-case hardening event that occurred 7-8 years ago on a double 20 bore rifle I built with a Turkish action made of 4140. I contacted Turnbull and asked him if they would take a action from me made of 4140 alloy steel that I would pre-polish and then for them to heat it in in their charcoal mix and crucible in their furnace to only about 1350-1375 degrees F (keeping it below the transformation stage as 4140 alloy steel will through harden and not surface harden) and then quench it as they do for color case hardening. They agreed to do that and the colors turned out to be stunning---not a hard surface but never-the-less beautiful. From the email that Turnbull Co. send me after the coloring of the action, I believe they were also amazed at the beautiful coloring.

If someone reading will be so kind to receive a photo of this 20 bore action from me via email and then post it to this discussion I will email it to them. Just send me a PM with your email address and I will email the photo to you.

Thanks bushveld. It is actually pretty easy to observe that when relatively high carbon steel is heated, the non magnetic point as the heat increases is a very sharp point. As the piece cools, it will remain non magnetic till it is noticably cooler. I don't believe it is good metallurgy, but high carbon steel can still skate a file when quenched while its non magnetic and below the curie point. It sort of sounds technical, but there are simple videos of observing the recalescence point of steel, basically black heat color seeming to heat glow again, as it cools. I'd like to see how your 20 turned out. Take care.

Stephen, send me the pics. I'll be glad to post them this evening. stanhillis@gmail.com

I bought my oven from a friend in Arkansas, now deceased, who showed me some guns he had "colored" using a charcoal pack, but keeping the temps even less than bush veld requested. The colors were beautiful. We're having it wired in and tested now. It has an analog temp gauge on the door. May not be the most accurate, but it's what my friend went by when coloring his gun's actions. We're going to play with it this winter and see what we can accomplish.

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

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

The colour thing is obviously personal taste. THough I do remember our art teacher stressing that blue and brown are a "discordant" combination of colours.

Two of the most attractively colored guns I have come across were a Holland and a Dickson sidelock, both displaying a rich grey silver patina that I guess was left after the original colour case hardening wore off. Does anyone know how to speed up the process of colour fading to get to this beautiful grey patina faster? Without resorting to power brushes that polish old guns making them look like fake coins.

Sure. If you want to not only get the sliver look but the wear pattern itself, put a little Simichrome paste on a cotton glove and handle your gun as you would carrying it and operating it. The high points will wear most quickly of course and the inside corners will retain color as they would naturally. This happens pretty quick (minutes, not hours). Clean and inspect every minute or two as you go. Works really to highlight engraving. In fact, I have a lock that needs this treatment.

In the video it seems the quench tank was filled just prior to the quench so the temp of the water is fairly cool. The water doesn't seem to be oxygenated as many people in the states do with compressed air. It appears the amount of the char , which keeps the oxygen from the part, is more important than having a sealed crucible. Also by using the heat of the crucible to dry the parts may also normalize the parts also. I've seen the normalizing bring out more color than achieved from just the quench. I've seen decent color achieved with temps from 1325-1425 F. Most of the older American guns frames are some form of a 1020 steel. Are the British frames a similar low carbon steel? We also don't know how long the heat soak was. Is one hour enough? I've been told 1 1/2 -2 hours. Getting the colors you want once is cool, being able to do it on demand over and over is the art I feel.

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