gem carving

[jvrjenivs]

The Romans had a good taste and had access to very nice jewellery (at least the more fortunate Romans), like nicely carved gemstones, like this example I found on an English Heritage website, but I know of enormous amounts of finds.



Now, I did some research into the modern way this kind of carving is achieved and all I found was to use a very fast rotary tool (stationary) with special diamond tips, and move the gem against it.

Now, does anyone on here has experience with this, or know what way the Romans would have achieved such carvings?

[PhilusEstilius]

Jurjen.

This is where we have to ask ourselves did the Romans have high carbon steel tools, and also did they simply have the same type of high speed rotary grinding systems as you have already suggested.
These kind of tools may well have been so fine that they have not survived, or indeed excavators today simply scrape them away in soil deposits without knowing it.
I do now and then find the odd intaglio in my metal detecting hobby mostly carnelian and some of the work is so fine,one must think that they even had magnification with glass.

[Epictetus]

I found some hints in good old Pliny.

When, by good fortune, this stone [adamas] does happen to be broken, it divides into fragments so minute as to be almost imperceptible. These particles are held in great request by engravers, who enclose them in iron, and are enabled thereby, with the greatest facility, to cut the very hardest substances known.

Pliny, Natural History 37.15

… so remarkably hard is ostritis, that with fragments of it other gems are engraved.

Ibid. 37.65

The best mode of testing is to strike off a fragment with an iron saw; but this is a thing not allowed by the dealers, who equally refuse to let their gems be tested by the file. Dust of Obsian stone will not leave a mark upon the surface of a genuine stone: but where the gem is artificial, every mark that is made will leave a white scratch upon it. In addition to this, there is such a vast diversity in their degrees of hardness, that some stones do not admit of being engraved with iron, and others can only be cut with a graver blunted at the edge. In all cases, however, precious stones may be cut and polished by the aid of adamas; an operation which may be considerably expedited by heating the graver.

Ibid. 37.76

Interestingly, there appears to be some question on what exactly is “adamas.” To a layman like myself I would guess diamond, but evidently some are doubtful. Perhaps the term could encompass other extremely hard substances. It is also interesting that apparently heating the tool helps the engraving process.

[jvrjenivs]

Thanks. In the meantime I found that in a book describing the gemstones from Nijmegen they actually go into this topic also. Not as deep, but they describe a tool called the bouterolle, which I think can be compared to a drill bit (round) of a rotary tool, covered in diamond dust). They even described a kind of evolution in the size and form of these heads.

Going to read some more about this for sure, and it seems appropriate to use a modern rotary tool with diamont coated bit for my engraving trials. (yeah, I hope I can show something nice in a couple of weeks, but I think it's going to be hard and a lot of trial and error)

[Arminius Primus]

Ave Fratres,

Pretty interesting posts!...but this got me to thinking,.... what did the engraving station look like and how did it operate? Maybe something like a foot powered potters wheel that rotated the graving tool, or a human powered drum arrangement that used belts to power it?? There was obviously water power.... but to get something geared down to provide a constant speed for engraving seems way complicated to me.

I guess the answer to the gem carving issue would also apply to the production of caged glass vessels as well as cameos and the like.

Anyone have an idea on what powered the graving tool??

Regards from a sunny, and pleasant Balkans, Arminius Primus aka Al

[Gaius Julius Caesar]

I used to watch asian jewelers using foot powered rotary tools, foot powered blow torches etc.
The Romans would surely have managed that too.

[jvrjenivs]

I used to watch asian jewelers using foot powered rotary tools, foot powered blow torches etc.

you should have taken pictures/video of that

And yes, that was also what I was not sure about when I posted the question.

[Gaius Julius Caesar]

I used to watch asian jewelers using foot powered rotary tools, foot powered blow torches etc.

you should have taken pictures/video of that

And yes, that was also what I was not sure about when I posted the question.

Hmmm, video was not around for the masses in those days...especially young children, not even 8mm. :wink:

Wish it had been though :roll:

[Arminius Primus]

Ave Fratres,

Great idea on the video, searched youtube using "foot powered engraving" and there are several videos of foot powered lathes etc. Maybe the closest use in our time period for something like that depicted would be for grinding glass but probably not gems. There was a foot powered grinding wheel featured that used old sewing machine components.

I guess the videos prove it can be done...... but the small sizes and fineness of the work still leave a lot of questions.

Regards from a sunny and quiet Balkans, Arminius Primus aka Al

[Gaius Julius Caesar]

Even the dentists used foot powered drills..... hock: :mrgreen:

[jvrjenivs]

but the small sizes and fineness of the work still leave a lot of questions.

At least that last comment I don't support. Simply, if we look at what kind of work the fine craftsmen in the Roman period (but still today in Brasil, India, etc) can be done, I believe it could be done without modern tools. You just need to be tought it from childhood onwards. I mean, I've seen those people in Brasil making totally awesome christmas cribs in a nutshell of only a couple of cm big, all by hand. It can be done, but need very good (and long) training of both hand and eye. (and I don't think that you can achieve this with modern (western) rules andif you're not started to learn at young age).

[Gaius Julius Caesar]

and the eyesight to go with it! i used to be able to focus on small things in minute detail when younger....ahhh, my wasted youth! :roll: :lol:

[jvrjenivs]

Great idea on the video, searched youtube using "foot powered engraving" and there are several videos of foot powered lathes etc.

Yeah, I've worked once with such a Lindsay's air engraver and that's just an awesome tool (but unfortunately also rather expensive )

[jvrjenivs]

and the eyesight to go with it! i used to be able to focus on small things in minute detail when younger....ahhh, my wasted youth! :roll: :lol:

Yeah, I still can do it (and sometimes for small jobs I don't bother to get my magnificent glasses out of their box), but after I have to set my 'view' back to 'normal' I can see it is no good for my eyes. D

[MARCvSVIBIvSMAvRINvS]

Plinius also writes about the quartz stone found near Ségobriga, Spain, which was used as see through windows for Roman houses, since it could be ground down untill it became translucent.

Romans must have had technology yet unknown to us, not nessecarily comparable to modern tech, but very clever indeed.

M.VIB.M.