Q: How should I sink some smooth depressions into the surface of a silver sheet? Do I need a dapping punch and block?
A: If you’re putting a depression in the middle of a larger sheet of silver, then the punch works well, but the block may be a mistake. The back side of the sheet in contact with the block may get scarred a little by the steel edge of the block as the silver pulls into the depression; and, more importantly, the sheet around the depression will tend to buckle. If you’re only making a shallow depression, though, it should work well enough. Certainly a dapping block is the quickest tool around for a first try, if you already have one. But they’re not cheap, and you may find it not only less than a smashing success, but not really needed in the long run. It’s a different story, of course, if you’re trying to create perfect hemispheres or domes from circles that fit into the block’s depressions.
Another option to consider is to dap the depression against a lead block. The lead will support the silver well, giving you a crisp impression without scarring the silver around the edge of the depression. But any lead residues on the silver must be very completely cleaned off before doing other operations, especially soldering or heating, to avoid contaminating the silver. Again, this works well as a fast technique to try if you’ve already got a lead block. But you still have to worry about buckling the surrounding sheet metal.
You can also set the sheet into chaser’s pitch, and use the punch against that surface. This leaves the silver freer to move with the punch than with a dapping block, so you’ll get less distortion of the sheet, and less tendency to tear as it stretches into the depression. But you won’t get as crisp a boundary to the depression this way, and you may have to chase and work both sides of the sheet to define the form you want. That’s a lot more work than just punching into the block. The dapping block is really designed for shaping hemispheres which end up completely within the circular depressions. For that use, it works very well.
The fastest and most efficient way to get a uniform flawless raised hemisphere or other form in the middle of an otherwise flat sheet would be to start with a piece of steel or thick acrylic plastic (Plexiglas is the most common brand—use ½ inch thick or more) which is large enough to support the whole piece of silver, and has the desired depression (which can be any shape) milled or carved into it. You can either carve the complete desired contour, or just a through hole with the right outline. The annealed silver is placed over that form, and then a piece of urethane rubber (die rubber) is placed over the silver, and then another piece of steel or heavy Plexiglas. This sandwich is then squeezed in a hydraulic press (You can build one with a 20-ton bottle jack from an auto parts store, at a cost of perhaps 75 bucks for the jack, and assorted steel for the frame). The urethane will force the silver cleanly into the depression without marring it, holding the rest of the sheet beautifully flat to the steel form, which prevents the buckling caused by other techniques.
This method has the advantage of considerable speed and repeatability for production use, but does require access to a press. The “Metalsmith Papers” give directions for building one, or you can buy a Bonny Doon press. The advantages are no scars, no mars, nice smoothly formed metal. With equipment costing a couple of hundred dollars or less and a die you can make in a half hour or less, you can get results similar to forms done in large striking presses with thousand-dollar dies. While it’s possible to achieve somewhat similar results with either a dapping block, or by using pitch, both will be a good deal more work, and won’t work quite as well, what with the buckling of the surrounding sheet.
Perhaps the most practical method, if you don’t have access to a press, involves making an open-backed die, sometimes called a Masonite die. This method can give you results almost as good as the hydraulic press method, but is slower. However the tooling costs are almost nothing, as you can build it from scrap materials. You use a piece of thin steel, and cut a hole to the desired raised or sunken outline. Make sure you slightly round or dull the edges of the hole to avoid scarring the silver. You make a sandwich of that piece of steel (for short runs you can use aluminum, or even hard Masonite, but the edges won’t be as crisp) with two pieces of sturdy plywood. Drill matching holes through all the pieces to allow bolting them all together. The plywood backing sheets need a hole that exactly matches the one in the steel sheet. This is then assembled with your annealed silver sheet in position over the hole in the steel, covered by the perforated piece of plywood, and then the sandwich is bolted tightly together.
You can then take your dapping punches and hammer them into the hole, which stretches the silver into the hole in the steel. The sandwich keeps the rest of the sheet flat, and the hole defines the outline of the depression. How much you punch it in and the shape of your punch determines the depth and shape of the impression. When it starts to get too work-hardened, you can disassemble the whole thing, anneal the silver, reassemble the sandwich, and work some more. But be aware that the silver is stretching as it goes into the die opening, and eventually will tear. There’s a limit to how far you can push a thin piece of metal. And, (a design note) keep in mind that this method can produce all sorts of shapes and sizes. Small punches are gradually worked around a small hole to create a smooth depression. With larger openings, you can just use ball peen hammers directly, without needing a punch. Remember that the die is only controlling the outline of the depression, and that the surrounding sheet metal will get pulled into the opening somewhat, though it is kept flat at the same time. The actual depth, smoothness and contours of the raised or lowered area are completely up to you, depending on how you push the metal with your punches.
The possibilities of Masonite dies are quite interesting, and facilitate a few things that those using classical techniques did only with great skill and difficulty. One good example is the “raising” of a flat tray, or plate. Doing this with just hammers and stakes and traditional silversmiths’ raising techniques is quite difficult, especially producing the flat edge and flat uniform bottom. The Masonite die method makes such forms almost easy to produce. With larger forms, by the way, Masonite actually works better than a steel form, as the softer edge grabs the silver less, allowing the silver to be drawn over that edge and into the depression with less tearing. Also, with such forms, the silver sheet needs to be rather larger than the desired end form, to allow for that “draw”, and often is made with holes to match the bolt holes on the die sandwich, but with those holes in the silver slotted out a bit to allow the metal to move towards the depression as it’s worked.
by Peter W. Rowe M.F.A., G.G.