Gold inlay enigma

[cootmans]

Can someone help me out with the following problem? I am restoring the barrels of a 200 years old Boutet shotgun. The barrels were primarily inlaid with some 210 gold stars, each 0,08 inch in diameter and a few ones 0,06 inch in diameter ! About 1 % of the gold inlay is left.
Under magnification one sees that under the now missing gold a small ( 0,03 inch !) copper disk is visible and under that is an even smaller punchhole ( 0,01 inch !)
In the attached pictures you will see the barrels,( yes I know it looks like something the cat dragged in) then a zoomed in detail were you can clearly see the stars, some with some gold, others with the gold missing but the copper disk visible and others with everything missing but in this way enabling to see the underlying punchhole. The third image is a drawing I made showing how the stars look from above and sideways.
This long explanation in order to ask this question : Why was the copper disk put there in the first place ? What use has it ? It must have been a tremendous work first punching the holes ( I guess a punch was made which included star form, hollow form for the disk and punchpin ) getting the tiny disks in place and then putting the gold on top.
I cannot detect any markings on the copper ( f.ex. points to hold the gold down or anything else) even not on the ones I stripped of the gold in order to examine the copper. I have put this question to several engravers and people working in the metal industry but all they could give me was a bewildered look ! So, is this a lost art ?
I am hoping someone can give me an explanation because when restoring I always try using the original methods and to come as close as possible to the original
Thanks for looking into this riddle.
Richard

 

[Ray Cover]

That is the dangdest thing I ever saw.

All I can say about it is that with so many of the gold stars missing it apparently was a pretty poor method of inlay.

Was probably a very beautiful gun at one time.

Ray

 

[Ray Cover]

I have been thinking about his. THe only thing I can come up with is this.

The center holes were a guide for the star punch and were probably originally drilled round and given that pentagon shape when the punch was driven home. My gues is that some sort of machine/rose engine/ gilliechette type process was used to remove a majority of the meat where the stars were to go. THen a punch gave the hole its final star shape. The machine could have also used the drilled holes for orientation on each spot a star was to go.

The copper is just a plug to keep the gold sheet from depressing into the guide hole when it is hammered in to place.

That's my guess.

Ray

 

[Mike Cirelli]

Ray I think your right about a machine being used, or punch. I think the copper center was to be used to hold the gold in by mushrooming down and the gold going under the mushroomed copper in the center.
Mike

 

[pilkguns]

I'm sure Ray is basically right. This is very similar method of star inlay as sold by Ngraver company. The copper was just a cheap and easy fill material as opposed to the more expensive gold.

I wonder if the gold came out because it was not undercut sufficiently or because there was some sort of galvinic corrosion going on between the steel, copper and gold that caused the gold to pop off. Richard, can you see any evidence of the undercut? would it have held the gold do you think? Was the copper as bright as it appears in the picture, or have you made it bright by cleaning down in the hole with something either chemically or mechanically?

BTW Richard, I will be in Aachen in a few weeks, and for sure will pop over the border to Phillipe Grifnee's place and finally make it over to Alain Lovenbergs I hope. Maybe we can catch up then depending on where you are.
regards
Scott

 

[Kerry Bogan]

I agree that they were probably machine done. There is a very symetrical pattern which you could do by hand but every star seems to have the same rotational orientation as if it were done in a jig, very unique.
Kerry

 

[John B.]

Richard.
I notice in the first photograph that there appears to be a bright "halo" around most of the missing star cavities.
Though I realize that this does not answer your question fully, it might be some clue to start.
This looks like a slightly different finish on the metal surrounding the missing stars.
It could be caused by stoning down the barrels where metal was raised by a star punch or by an undercut
using a chisel.
As Ray, Scot and Mike said, the hole might have been to guide the punch.
It looks as if the stars are all alligned.
A pentagon shape hole with a matching guide on the star punch could do this allignment.
This shape of the guide hole could have been modified from an original round hole using a pentagon punch guided from the side of the barrels by a simple fixture.
The copper disc was probably to stop the gold from flowing into this hole.
It may also have served to raise the center of the stars if they were seated with a recessed seating punch.
They could be flush now from the same wear that removed the others.
All just guesses on my part. As Ray said, I bet it was something to see when it was first done.
Thanks for the great pictures and drawings and brain teaser.
Best of luck with this very interesting project.
John B.

 

[Ray Cover]

Common guys, somebody has to have the answer to this. The curiosity is killing me.

This surely isn't the only gun that was ever done this way.

Ray

 

[Marrinan]

Richard,
while many of the engravers have made sound speculation on mechanical means what about the copper being placed in the holes to act as a heat sync used to help in the evaporation of murcury IF the gold were suspended in the murcury and formed into a damascasine(sp) gold paste then heat applied from inside the barrel to evaporate the murcury-It seems to me that the French gun trade during Louis 14, 15 and 16 as well as during Nepolianic regiam did this type of work-My 2 cents-Fred

 

[cootmans]

Hello again,
I will try to answer your questions as complete as possible.
Ray,
I think your are right about the way the star was punched. Under the microscope I was able to see that were the center hole starts (thus at the bottom of the hollow form were the copper is) the sides are a bit caved in. This follows indeed your reasoning of a center hole first as a guide and the final star punch afterwards.
If the copper was used as a plug it sure was a lot of work just for keeping the gold from getting in the punch hole. With the extremely tiny size of the copper (0,03 inch diameter!) it is questionable whether the amount of gold used would have mattered very much.
Mike,
The copper definitely was not used to hold the gold down. I stripped the gold of one of the remaining stars and there was no mushrooming down under the copper.
Scott,
Many years of neglect have worn the barrels to their present state. A lot of gold disappeared by wear and tear. Underneath the gold was indeed a green sludge (corrosion of the copper as you suspected) and this also must have caused the gold to pop out. I lightly cleaned the copper for it to show in the picture. With the steel worn down so much I could not see any undercutting, even under the microscope.
Thinking logical I guess that there must have been some undercutting, three undercuts in each star would have been sufficient. But what job considering the size !
I live in Melsele, a village about 7 miles west of Antwerp. Distance to Alain Lovenberg is 120 miles. I don’t know your schedule but you are welcome. I must warn you that if you come you have to pass by Brussels on the ringroad and the traffic there is hell with traffic-jams each day. I am on holiday from May 10th. till May 25th.
Kerry,
The pattern is indeed symmetrical and the rotational order without flaws whatsoever, so I think you are right with the jig thing.
John,
The bright “halo” you see is from me cleaning the barrels a bit with fine steel wool.
Your remark about the copper disc being served to raise the center of the stars is interesting. It may have caused the gold to worn quicker and fall out. Can you describe the recessed seating punch you mention ? I don’t have a clue what it looks like or how it is used.
Marrinan,
The process you describe is called fire gilding, and was indeed extensively used in the periods you mention. It is an extremely dangerous process.
I don’t think the gold was applied in this way because the heat needed to vaporise the mercury and deposit the gold would have loosened the barrels, which are soldered together. Also the gold I stripped from one of the stars is uneven in thickness and on the other hand too tick for it being a thin deposit.

Thank you all for your help and quick response. I hope I can help you out one day.

Best regards

Richard

 

[John B.]

Richard.
The seating punch could be made of steel with the star form relief cut into the end of it, much like a very small coining die.
This could have been made from round rod stock with a flat ground on one side for allignment purpose.
It would have needed a simple fixture, perhaps guided from the barrel or rib edge, to keep it alligned.
This fixture would have a hole to fit the diameter of the forming punch.
A flat ended set screw would guide against the flat side.
Again, just speculation on my part.
But that's how I would do it to start forming raised shaped stars. Then clean up with gravers.
Best wishes and luck with the project...... rather you than me!
John.