Help, please: Darken Gold Lines

[rmgreen]

I have fought this problem for many years as a gunmaker and hope that some of you will have figured out a better way. In the process of blackening metal (rust bluing) one must "card"(remove the black oxide) from the surface of the metal. Metalwork/engraving which has gold(24k) inlays gets embedded with this black oxide and darkens the soft gold. The problem is how to return the darken gold to its original brillance. The best solution is not to get it embedded with this oxide at all but how? I use 0000 cleaned steelwool as the carding medium on gold inlays but the problem still presist.

Roger

 

[John B.]

That is an interesting question, Roger.
Have you also posed it to the ACGG ?
I'll look forward to seeing what answers you get.
Please be sure to post them here, please.
Best regards.

 

[ken dixon]

Hi Roger,

Welcome to the forum, it's nice to see another member from Wyoming, I looked at your website. It's nice, very cool dog site.

Ken

 

[Arnaud Van Tilburgh]

Welcome to the forum Roger
For removing oxide on gold we goldsmith use "safe pickle" or sulfuric, but this will have a reaction on steel.
arnaud

 

[SamW]

Hi Roger, long time no see! All the finishers I have delt with struggle with the same problem and if anyone comes up with an easy answer they will be blessed! The gold can be cleaned a little bit with a nonabrasive eraser but I don't think it can ever be brought back to a perfect state. Regards.

 

[Marrinan]

Roger, If I recall correctly, Lynton McKenzie recommended cutting the dovetail, as opposed to raising a burr caused by chiseling, when carding was to be done. I seem to remember him talking about laying in the gold post blackening. It seems to me that he talked about using soft punches that would leave no mark on the steel and using copper chisels to cut the excess gold away. Then doing your shading. He said that because of the highly finished (knives in the discussion) the engraver should finish these last and that the piece should be complete when the engraver finishes no sanding of any kind ever required. That was McKenzie-perfectionist personified-Fred

 

[BJREBUCK]

Roger,
the best solution i've found is to spray the gold with wd40 or some other penetrating oil, then card with 4/0 steel wool and/or white scotch brite.
This has worked for me for many years. Give it a try. The oil will loosen the
embedded oxide and lift it out of the gold.
Brian

 

[metalchipper]

Roger,
the best solution i've found is to spray the gold with wd40 or some other penetrating oil, then card with 4/0 steel wool and/or white scotch brite.
This has worked for me for many years. Give it a try. The oil will loosen the
embedded oxide and lift it out of the gold.
Brian

Works for me all so.

 

[jerrywh]

I just use a red rubber erasure. I also found that part of that trouble comes from excessive rusting before carding. If the rust is very fine and light it does not seem to imbed in the gold near as much. Best to do very light rusting and a few more cycles than to rust heavier and rush the process. I card after about an hour or two of rusting even if the metal doesn't look very rusty. I card with a .003 diameter wire brush from Brownells and run it a a low rpm . about 700 to 100 rpm.

 

[DKanger]

In addition to what Jerry said, you can also card with burlap or very coarse wool blanket material. You don't really need an abrasive material, just something to remove the "loose" red rust, not the converted black oxide.

 

[Kevin P.]

This is an interesting question for goldsmiths.

What's a problem for gunsmiths might be useful for goldsmiths. It's very difficult to darken high karat gold. An antique finish is sometimes needed.
It's copper in lower karat gold that reacts so it's interesting that high karat gold reacts to what ever you use. I'm assuming that it is high karat gold that you use.
Kevin P.

 

[SamW]

Kevin, it is the black oxide from the rusting process that gets embedded into the soft surface of the gold, not a chemical reaction.

Brian, is that a final carding off with the WD40, or do you use it between stages?

 

[Kevin P.]

Sam, any idea how durable that black oxide is? I'm thinking of its durability on gold rather than on the firearm.
Kevin

 

[fegarex]

Kevin,
The gold actually never gets "colored" by the black oxide process but gets darker when the excess is carded (wire brushed) off the steel imparting the small particles into the soft gold.

 

[BJREBUCK]

Sam, the wd40 is used after the final carding. You don't want
anything to contaminate the steel during the blacking cycles. The white scotch brite will leave the gold with a brighter finish than steel wool if that is desired. As an aside, the late terry wallace
always did the final detail on the animals, etc. After the blacking as finished to aviod any degrading of the cuts.
Brian

 

[rmgreen]

I would like to thank all of you for your replies. By your replies I find that every one has the same problem as I and that there is nothing much new about this problem. I had not tried the penetrating oil ( I used kroil). I tired this for the first time yesterday and found that this method was little better if better than what I have done for years. In the gun trade here in the USA I believe that Pete Mazur is one of the best and if not the best in our country. I will copy his answer to me when I posed the same question I posted here.

"To begin with gold looking like it was caustic blued is not going to happen. The caustic bluing cleans the gold. I use oooo steel wool. The worst offender is thin gold flush inlay as you have stated. I rub the gold inlay rather vigorously when I am carding the part. If the gold is not bright enough then I mask off the gold and very carefully using a shaped Pink Pearl eraser I clean the gold with the eraser. I use the eraser after the job is done and the part has been oiled."

Logically I want to take this one more step. Has anyone caustic over blued rust bluing? If so did the part retain the good qualities of the rust bluing and the caustc bluing clean the gold? If in fact the gold is cleaned by caustic bluing which I question. I suspect the gold is in its normal finished state as engraved and that the caustic bluing only added the contrast to make the gold leap out at you. If no one has run this experiment I will do so at some point when time allows.

The rust bluing process is different for everyone doing it. There are many variables and these variables are affected drastically on where you live. If you are going to receive consistant results then these varables must be controlled where ever possible. One poster indicated carding red rust. One should not have any noticable red rust after boiling out. The boiling out process converts red rust (ferrous oxide) to black rust(ferric oxide) and there should be little ferrous oxide after the boiling out. I had this problem many years ago when I started in this business. I found the cause to be altitude! I live 1 mile high here in WY. Water boils at 185-187 deg F. and I got red oxide and could not get the true black oxide finish. I found that I had to raise the temperature of the water to 200+ deg F to get the black oxide finish desired. I made my boil out tank into a pressure cooker of sorts to raise the temp. I put a lid on it and that was sufficient to raise the temperature above 200 deg F and provided a nice black oxide finish. The chemicals used and the age of these chemical also have an affect on the final color and do not forget that guns are made of all kinds of steel all of which are differently affected by the chemical used and the results you get as to color, grain structure of the rusting. I use several formulas of chemicals. A sweat box is absolutley necessary if consistant results are to be gotten and that all oxidation of the metal be maintained at a certain humidity/temp level. Here in WY I st my sweat box up for 90 deg temperature and relative humidty of 83 percent for consistant results.

If I find a solution to the darken gold problem I will pass it along if some of you find a solution please pass it along.

My best to all of you and thanks again for your time, valueable experience and offer to help.

Roger

 

[Kevin P.]

Thanks Rex, that answers any questions about usage for other purposes.
Kevin P.