Repoussé III: “Chisels, Lead Blocks, and Stamp Work”
This is the third installment of the writings of repoussé artist Nahum Hersom, who passed away in April.
The process of Repoussé in itself is not practiced by many folks these days, so we must all make an effort to document the knowledge of the men and women that had these skills, in an effort to preserve, learn, and finally teach what they knew, otherwise these processes may die and be lost altogether. Nahum Hersom not only had a depth of knowledge in repoussé process, but had a keen sense of understanding in other processes that complimented and fortified repoussé. Making the myriad tools and dies is part of that process, and the information that he has written expands on making these tools and dies. We might lean towards what Nahum already knew, but there are those minor, and sometimes major details that can make or break the process. So, sharing these writings is not just for you or for me…it is for the ages.
Note: Where there are parenthesis, I have either added or rephrased words for better understanding.
Plus…This text contains instructions regarding the use of toxic materials. Please refer to MSDS information when using these materials, i.e. lead, and zinc, etc. I am printing these instructions as Nahum wrote them. I am not responsible for the misuse of these materials, which can result in illness or death if improperly used.
All chisels for sheet metal (are) approximately 4-1/2″ to 5-1/2″ long. Forge (the chisels) square with well-rounded corners and barrel, or (forge to a) tapered design: top end smaller to control (the) energy from (the) hammer, so it goes through (the) center of (the) chisel.
Cutting edges for straight chisels are slightly rounded so corners are relieved to prevent corner breakage (on the chisel.) The width of (the) curved chisel edges will correspond to the radius being cut.
This prevents steps as one gets with a straight edge chisel, (and) saves a lot of filing. Curved chisels have beveled edges inside or outside to correspond to the design, as Gothic designs where edges of cut-out work are tapered.
“Walking” chisels for cutting sheet have one corner of (the) cutting edge curved up, and a slight angle, (as the) chisel in held at an angle. When struck (this shape) will help move (the) chisel forward, so the chisel does not have to be lifted for each blow.
Walking chisels are used to cut out designs in lamps, letters for painting logos, door locks, etc.
Chisels take a lot of abuse, so use a good grade of tool steel, and temper (them) carefully. Sharpen (the) chisel edge…one side only…to to get bevel edges for door and knocker plates. These are cut on a soft iron plate, or (other) cutting plate.
Lead, (can be) melted and poured into shapes (for) bench blocks, (and) other repousse’ or punch plates. Lead bench blocks are mounted on (the) rear of (a bench or machinist’s) vise. Pour lead into forms approx. 3′ x 3″ x 2″ thick, or slightly larger, and 4″ x 4″ x 2-1/2″ thick. (Nahum) has a square pan made of 1/8″ plate 1/2″ larger than (the) square of (the) lead block, with 3/4″ sides to keep lead in place. Put a piece of heavy truck inner-tube in (the) bottom for (a) cushion. This pan has two ears welded to (the) bottom side. Drill (a) hole through (the) ears, through the back end of (the) square vise bar, so this unit is connected to (the) vise bar, to stay in place. Be sure to taper both sides of (the) lead casting block pan enough, so (the)lead can be (easily) removed.
After (the) lead is removed from (the) forms, put (the lead) in (an) oven at about 300 degrees to anneal, especially if (the) lead comes from auto wheel weights.
Pure lead can be bought from Non Ferrous Metal companies. They have many alloys of various hardnesses. Plumber’s lead is soft. Pure zinc can be used to make a forming die to press soft metals into (it), as per rubber press. Zinc or kirksite is quite hard and can be repaired with (the) torch and pot metal rod, or (you can also) make filler rods of zinc scrap.
By pouring lead into other forms and sizes as needed, (i.e.) cylinders, mushroom heads, squares, etc., that (can be) held in vise jaws, one can form smaller areas not easily done on (the) large block on (the) back of (the) vise. Also, pouring lead in back of forms that you are working on as a back up material, will facilitate working on difficult areas, using various hand-held tools, (i.e.) punches, veiners, etc. Often, especially in reproductions, when small castings are necessary, carbon blocks or dental plaster can be used to make a form that can be filled with lead or zinc.
Use lead blocks to size as needed. (Nahum) uses (a) 6″ x 6″ x 3/4″ block. Use on a solid surface, such as a hardwood stump. Make a frame of iron to hold (the) sheet metal firm (onto the) lead block around (the) edges. With this process, one can make stamped jewelry, medallions, etc. On some work, one can chisel-cut out backgrounds which leaves (a) raised design. These can be riveted to another plate as per locks, etc., to have several depths showing.
For Larger Work, As for Medallion and Plaques:
Sheet copper on top of lead sheet:
Use 1.2″ steel plate on (the) bottom. Put 1/8″ leather on (the) plate. Then place 1/8″ lead plate on (the) leather, and clamp down (the) frame to hold (the) copper/lead/leather, to steel plate.
To reproduce objects as drawer pulls or other parts with designs pressed into them, i.e. jewelry, first make a clay copy (male); use silicone rubber mold substance to cover (the) clay (to) get a female pattern. Use plaster of Paris to stiffen the outside of the rubber mold, and remove the male mold from the clay.
Fill (the) rubber mold with dental plaster, and get a male copy in plaster using molding and art foundry molten metal techniques. One can get a female mold pattern in metal. This then can be used to impress (with a) rubber press, a thin sheet of soft metal into (the) die recesses until the design is perfect.
(Nahum has) used cerobond or cero matrix to make the female die. It melts at a low temperature and is easily repaired with tin solder, and a solder iron. If (the) design details get damaged, use engraving chisels to rework (the) design. Also, some work can be done on plasticene, as a back-up material in lieu of pitch. Also, cerobond metal will make a die for repeat work, but is softer than zinc.
(End of installment.)
foobert - January 4, 2016
Kirksite metal isn’t available in the USA any more. Zamak 2 is an alloy that is nearly identical and can be substituted for this purpose.