ENGRAVING ON BOULLE
Welcome to part 4. The content of the previous blogs in this series will be familiar to many of you already doing marquetry. Though I guess my use of epoxy glue, and the issues related to the significantly different thickness of the materials might be new. They were for me, however the biggest new aspect of this whole Boulle marquetry project was the engraving.
Having used brass, pewter and tortoise shell in my panel designs they were further enhanced by engraving. In some ways it is similar to the sand shading done on ‘painting in wood’, though with engraving, the shading is done with fine lines. However, as well as shading the cut out metal shapes to add depth to the design, extra elements can also be added to these cut out shapes, like extra leaves, petals, or whole flowers
While it is the brass and pewter that was usually engraved, some antique pieces also have the tortoiseshell and wood veneer engraved. Additionally the engraving of the Premier Partie and Contra Partie is different. In Premier Partrie the shading is done on the metal leaves, flowers and stems, to add depth, with veins in leaves, petal details in flowers, and shaded areas were stems cross. In Contra Partie where the metal forms the background, lines are engraved in the metals around the leaves, flowers and stems to accentuate them.
These engraved lines on the metal and tortoise shell are then filled with a matt black pigment. Traditionally soot and/or charcoal mixed with shellac was used as a filler. Additionally gold paint sometimes used on engraving in the wood veneer and tortoise shell on Contra Partie.
There was as much if not more, for me to learn about engraving, as there was with the rest of Boulle metal marquetry process. I used two excellent web sites as my main sources of information on the ‘art’ of engraving. Sam Alfano’s iGraver.com site, and Steve Lindsay’s engravingschool.com site. They are aimed mainly at the engraving of weapon, where guns, rifles, knifes etc are engraved with extremely fine scenes and detail after purchase. But they were invaluable – I couldn’t have managed without either of them. They are packed full of information, practice videos, tips, tooling, and discussion forums.
I was aware of the various methods of hand engraving for my initial research:
1. Holding the graver/burin and just pushing it with your hand.
2. Holding the graver/burin and tapping it with a hammer.
3. Hand pushing a pneumatic engraver
I tried the first two on some practice plates and decided it was just too difficult, I slipped, went over into adjacent bits and pieces, and didn’t find I had much control of the depth and thickness of the lines. I guess practice would have helped.
I decided to go down the pneumatic engraver route. After lots of internet research on the range of pneumatic engravers, looking at YouTube videos, and the discussion forums mentioned above, I took the plunge and bought a relatively cheap Chinese machine from Aliexpress.com
The GraverMate cost me just A$280 delivered – great value I thought. To power it I borrowed a friends compressor. Make no mistake this is still hand engraving, but the tiny pneumatic impulses to the graver tip, which is controlled by a foot peddle, mean that it requires very little hand pressure. You let the pneumatic impulses do the work, a bit like a mini jack hammer!
Other things I had to purchase where, some 2mm square HSS steel bar, so that I could make my own gravers. The graver bit with the yellow end shown in the picture above was of no use. To sharpen my gravers I made myself some sharpening templates based on the patterns on Steve Lindsay’s site. These were invaluable in getting a well profiled and sharp graver tip. I made a Universal one for the main lines and a Detail one for the fine shading lines.
Graver sharpening templates
The grinding angles are slightly different on each set. The small template is used to grinding the graver to its reduced profile, with the larger one then used to hone the cutting bevels on the heel and front face of the graver tip. As the graver becomes blunt this larger template is used again to re-hone the heel and cutting face.
To grind the gravers to the correct profile I purchased a lapping wheel which I fixed in my pillar drill, and some super fine sharpening stones for putting the final cutting edges on the graver tips.
Lapping wheel fixed in the drill press, in use with the template
Sharpening stones and lapping plate
Acrylic Lapping plate and stone in use with the template
A sharpened graver tip
The last thing I made was an engraving Turntable using a ‘Party Susan’ bearing that I could fix in the vice. This enables you to rotate the panels as you work on them. The technique is to rotate the panel towards the graver tip when doing curved lines, rather than moving your hand/arm around the curve.
A end panel on the Party Susan turn table fixed in the vice
Finally, so that I could do some practice engraving I also purchased a few 10cm square brass plates.
Tuning the Graver Mate was a key element of the learning process. This is a combination of:
- the input air pressure from the compressor
- the impulse speed, adjusted by the knob on the Graver Mate
- length of stroke of the hand piece, adjusted by threaded sleeve on the hand piece.
My Chinese Grave Mate came with very minimal instructions, which are verging on the useless!!! The machine however is more or less a ‘rip-off’ of the GRS Graver Mate and GRS Graver Max machines. Yes I could have bought one of these ‘superior’ GRS machines for US$850 – 1500, but remember my Chinese Graver Mate was just US$211.
So to tune my Chinese version I used the following link to instructions for tuning the ‘real’ GRS versions.
I was now ready to give it a go, and followed some of the tutorials on Steve Lindsay’s web site mentioned earlier.
DEVELOPING MY ENGRAVING TECHNIQUE
I instantly found that I had far more control with the pneumatic engraver after my very limited success with a hand pushed version. I hardly slipped, found the engraving relatively easy and my skill levels progressed rapidly. The fine control of the engraver via the foot peddle improved, and cutting straight, curved and varied thickness lines progressed as well.
One of the first panels, showing the fine shading lines – these have not yet been filled with black pigment.
But it was time consuming – though not quite as bad as sawing the marquetry in the first place. Engraving one of the box lids, 30cm x 25cm took me around 15 – 18 hours. It also gave me back ache as I was crouched over the panels with desk light blazing and a magnifying loupe stuck to me head. An adjustable stool would have been good!
The main difference between Boulle and ‘normal’ engraving, that is done extensively on guns and pocket knives etc, and Boulle engraving, is that in Boulle work most of the outlines of your flowers, stems and leaves are already delineated, as you have cut them out of different materials. On more usual engraving you start with a blank piece of metal and have to drawing in all the shapes as well as the shading. So in Boulle work, most of the engraving is actually the fine shading of the flowers, leaves and stems to make them look 3D. So there are very few heavier lines, where you ‘draw/engrave’ the outline of the shape before shading it in. It’s more about fine lines and varying their thickness. You can also vary the lines profile by tilting the engraver to one side which gives a different bevel to the line which adds depth to the ‘picture’.
Before I actually started engraving the panels I needed a pattern to work to. I printed off some of my original sawing patterns and used a pencil to draw in any stems, petal outlines, and internal leaf outlines. I tried different ideas before settling on the ones to use. I only had to do half the panel as it’s was a symmetrical design. I found the best method was to draw the same element in each quadrant, before moving on to the next element of the design. With the main lines sorted I then printed off another saw pattern and put in all the fine line shading. Different colored fine liner pens were good for this, though a pencil meant you could rub out mistakes on the patterns.
I marked these main veins, petals and any internal main outlines directly onto the metal with a pencil. I followed my paper pattern rather than tracing the lines onto the metal. Drawing the same element in each quadrant before moving onto the next element of the design became the way I worked, and saved missing bits out.
These main lines were then engraved with the Universal profiled graver. I got better at varying the line thickness and its depth as I progressed. I still had the odd slip, but nothing too serious. I must say I started engraving a rear panel first before progressing to the sides, the front and finally the top – the part you see most!
With these main lines done, I started engraving the fine shading and detail. I used a Detail profiled graver for this. I didn’t mark any of these on the metal as before, but used my paper shading pattern as a reference, and generally made it up as I went along. But, I still did the same element in each quadrant to save confusion, before moving onto the next.
The difference between engraving brass and pewter is significant. The pewter is so much softer, like butter that’s been out of the fridge for an hour or so. Whereas the brass is like hard cheddar straight from the fridge!! The pewter therefore requires a much, much lighter touch. I therefore generally started the day by working through a load of pewter engraving as I had got used to the light touch. I then moved onto the hard brass where a heavier touch was needed. I never went through the pewter with the graver, but think it might be possible even though it was 1mm thick.
In between engraving I would lightly rub down the panels with 800 grit to get rid of any burrs that had started to stick in my fingers!! But this had to be done lightly and in one direction, so as not to sand through the engraving. As my skill improved I left fewer burrs behind, as I became proficient at exiting the metal cleanly with the graver, rather than breaking off the chip, which left a burr.
FILLING THE ENGRAVING
With the engraving finished I lightly sanded the panels again. Sanding in one direction I working through 800, 1200, 1500 micro mesh, and sucked off any dust with my shop vac. I carefully degreased the metals and engraved lines with Isopropyl alcohol on a cotton bud. This was to help the ‘filler’ stick. An alternative would have been to use Acetone as a degreaser, but I was concerned that this might affecting the faux tortoise shell.
The panels were now ready to have the engraved lines filled. Traditionally soot and crushed charcoal was mixed with shellac and rubbed into the engraved cuts. This also helped to fill any bits of saw kerf that was still unfilled. However following the engravers forums mentioned above, I went for Flat Black oil based paint.
A quadrant of a top with matt paint filling the engraved lines.
I filled a few other small kerf gaps and grain holes with superglue and an appropriate saw dust. When the surface was dry I rubbed the flat black paint into the engraving using a cotton bud. Generally I dragged the cotton bud across rather than along the engraved lies where I could. This was left to dry before lightly sanding it off with 800 grit, and blowing off the dust with my vac.
Holding the sanded panel under a desk light and rotating it, made it easy to see the bright reflections where I had missed filling some bits of engraving. This required another go with the paint and cotton bud to touch these up. The fact that the surrounding wood grain had been sealed with my dilute polyurethane ‘sanding sealer’ meant that sanding the paint back to bare metal, and wood or tortoise shell again was easy. When I was happy that all the lines were filled I again worked through 800, 1200, and 1500 along the length of the panels.
I’ve only done a small trial so far with the faux tortoise shell, but I’ve found I can successfully engrave it with the GraveMate.. To fill these engraved lines I’ve used gold paint instead of black paint. We’ll see how a full panel goes later.
So far I’ve done the engraving on the two Permier Partie boxes, both of which required a lot engraving!
APPLYING THE FINISH With the engraving completed, lines filled and the panels back smooth, they were ready for the finish to be applied. The boarders did need some selective fine sanding where pewter and brass dust had discoloured the boxwood stringing.
Traditionally as with most antique furniture French polish/shellac was used. I’m not a fan of it, and prefer a more durable polyurethane finish. I decided the ‘rubber’ technique, whether French polish, or the use of ‘wipe-on’ polyurethane was too risky, as was using a brush. I thought that either method could pull some of the black paint out of the engraving. So I applied one coat of spray on satin polyurethane to seal everything, and then another 2 or 3 brushed on coats of satin polyurethane before I started sanding the surface flat again.
I did this sanding with a palm sander and 500 and then 800 grit abraflex pads. More brushed coats of polyurethane were applied and sanded until I had a flat filled surface. Finally I finishing off with 1000 and 1500 grit and then three grades of micro mesh cloth. Wax polish was applied with 0000 steel wool, left to dry off for a day, before buffing with a soft duster.
Two close-ups of the top, filled sanded and finished.
Of course the panels then needed assembling into the box, the interior trays and drawers completing, and the locks and hinges fitted.
A finished box – only four more to go!!
Completing the other four is going to take another 6 or 8 months at least. But they will have kept me quiet and out of mischief for quite a while.
Thanks for looking. Please contact me if you want more detail on any aspect.
I’ll post more about the Contra Partie engraving when I’ve actually done some.
-- Madburg WA