Chasing – a specialty technique where punches are used to press a narrow line or large area that becomes background.
-the tool is usually drawn toward the worker, at an angle that propels itself along
-the tool maybe dipped into oil to lubricate its travel
-a raised element is created by lowering the surrounding metal
Chasing is an ancient technique to incise lines into metal, the result resembles stumping. The tool moves in a steady unbroken motion. Patterns can be created on flat or shaped sheet metal and used to sharpen details on castings.
Preparation: The metal to be colored must be clean. Avoid preparations with greasy material such as steel wool and buffing components. Instead use pumice, Scotch-Brite sand paper and a scratch brush. Clean surface with an ultrasonic, when clean water will sheet , not bead-up. Dry in a box of sawdust. Handle work with edges and wipe with alcohol before coloring.
Simple Copper Plating
Brass is hard to darken. One can plate the object with a thin layer of copper, which can easily be colored. Saturated pickle solutions (blue-green) is an acid charged with free copper ions. They, with electricity attach to a metal object.
Most metals react with their environment. This produces colors and corrosion. To maintain a patina, the metal must be returned to its original finish periodically or sealed off from its environment. A hard film lacquer will resist marring but will eventually be chipped away. A soft film wax is more vulnerable, it will smear and rub off.
Apply a thin coat, avoid bubbles and trapped dust. Multiple thin coats are preferred over a single thick one. At times, previous materials contained oils that can’t be totally cleaned and this can cause lacquer to bead or dissolve.
Beeswax and paraffin are commonly used to protect metals. Application can be by heating the object and rubbing the wax over it. Also, you can reduce wax with turpentine and rub on piece. Avoid any time that will import silicon on to surface.
Chemicals rather than mechanical force is used as metals are given controlled exposure to acids for specific durations to create desired effects. The design is cut into metal with acid by covering part of the metal with an acid proof material (resist) while leaving areas exposed to the corrosion (bile) of the acid. Varying depths are achieved by; etch a wide, remove piece, rinse it and allow the areas that have suffered depth to stop. Allow the fresh resist to dry and re-submerge. Repeat previous steps until etched depth is achieved. This technique has been used for over a hundred years for chapter rings etc., in place of broader strokes of hand engraving.
Mordants are acids that are deliberately used to corrode metal. For brass nitric acid is used and for steel hydrochloric acid; both are acids used in the etching process.
A polished appearance is the result of a perfectly flat surface. Under magnification, a cross section of scratches looks like this; light is refracted around and in between the scratches, like sound going through moisture. A flat surface gives back no etches, resulting in a highly reflective surface. Files define shape on surfaces. Abrasives are used on flat surfaces after being wrapped around a flat stick for abrading.
1. Bobbing – gray – contains pomice fast cut
2. Tripoli – brown – sandstone material fast cut
3. White – fast – no diamonds
4. Diamond – cuts are fast as Tripoli but leave a brighter finish
5. LEA – fast cutting for steel
6. 7AM – man made fast cutting
Piercing, when done correctly, sawing is a relaxed and rhythmic experience. The sawn piece must be held securely horizontally. The blade teeth must point forward and tightly strung. Begin by drilling a hole in each compartment to be sawn.
This ancient process gives form to a sheet of metal by pressing it out from the back and in from the front. An addition to a range of repoussé depends on the plasticity of a supporting material that holds the work metal. The word comes from the French verb meaning “to push back”. Simply stated, repoussé is the process of creating volumetric forms by pushing metal. The pushing is usually done on the front and the back. Warmed pitch in a support container gives support while form pundring takes place.
Once a dial or mechanism were cut into semi flat surfaces in the late 17th or early 18th centuries, only “high mark” movement makers took the surface to the next level by planishing. The Latin word planus which meant to flatten or level. It refers to the smoothing, toughening and polishing of metal by hammering. The effect of planishing can only be as good as the surface being used. Hammer stakes and anvil must be mirror-finished. Blows are overlapped in a slow process.
Heating a metal near to its melting point makes its crystals move apart, opening up microscopic spaces. Soldering is to introduce an alloy that is fluid just at the point of maximum expansion. This alloy solder flows into the spaces of the expanded metal. Not to be confused with soft soldering, which uses an alloy of tin, lead and similar metals. Soft solder flows at temperatures about a third of those needed to cause the crystal spaces to open. The holding power of soft solder comes from its ability to fuse onto clean metal. Since the grip is only surface to surface, the soft solder cannot be filed flush without weakening the joint. This is not true of gold or silver solder.
It is the amount of zinc in silver solder that controls its melting point. When melting solder, care must be taken to avoid overheating because the zinc will go off in a vapor, changing the proportion. Each time the same amount of solder becomes fluid, its melting point is raised. Overheating a previously soldered joint will burn out the zinc and can leave a pitted seam.
Gold may be joined with silver solder. To achieve a color match a gold-based alloy is usually used. Gold should be a karat or two below then the metals being joined. 10k will be a solder for 14k; 14k will be a solder for 18k etc..
- Spelter is another name for zinc, today the word is used to describe brass when it is used as a solder for steel in the process called brazing.
- Good fit – Hold work up to the light to check for gaps
- Work clean – No oils, grease, pich, buffing compound etc.
- Flux – Flux is needed to absorb oxygen
- Even heat – All soldered pieces must reach soldering temperature simultaneously, take into account steel mesh, tweezers etc.
- Solder flow – Solder flows toward heat, don’t direct flame at the joint, let heat travel through the piece
- Right size – Use enough solder to fill the seam
- Incomplete or un-solderable joint – Not enough heat, dirty metal, no flux, prolonged heating
- Solder balls up – Heat may be flowing away from the joint, dirty metal or solder
- Solder jumps to one side of joint – One side may be hotter than the other, reflux and repeat
- Soft solder – If placed in the wrong location can be chemically removed
- 3 ounces acetic acid with 7 ounces of hydrogen peroxide
- heat but not to boil
- The history of civilization can be traced through the ability of each to control fire
Flux comes from the latin word to flow and refers to the chemicals that facilitate the flow of the solder by preventing the formation of oxides. Fluxes work by forming a coating that protects metal from oxidation. Their solvent is water, after being applied, the water evaporates leaving a clear glossy coating skin. Flux acts as an oxygen magnet by providing a compound that is more attractive to oxygen then the metal being soldered. As oxygen and other elements combine with this coating, the protective powder diminishes, a change often seen is a blue or green tint in the flux.
Pickle is a strong chemical both used to dissolve surface oxidative and flux residues from a metals surface. Pickle is used to clean sterling or karat gold, it absorbs copper ions creating a super saturated solution. This then can be turned into a copper plating solution, loaded with copper ions, loaded with copper ions ready to plate a metal object. Both heat and electrical charges increase the plating response.
Firescale is an insidious deposit of cupric oxide that grows within the structure of some copper alloys that are heated in the presence of oxygen. These oxides form quickly, one, cuprous oxide a black surface layer that can be dissolved in pickle and two, cuperic oxide which is a compound that forms simultaneously in the metal.
1. Use a hit and run solder technique
2. Avoid prolonged heating
3. Use a large enough flame to get the job done efficiently
4. Use enough flux, it absorbs oxygen and prevents it from combining with copper
5. Do not overheat the metal when soldering
Firescale can be removed by dipping the work in a nitric acid solution. After all soldering and rough finishing are done, dip then polish
Fusing is connecting pieces of metal by heating them to their melting point and allowing the puddled surfaces to commingle
Rivets are a member of a large family called cold connection. They are pieces of rod that are slid through a snug hole and upset or bulged over on each end to lock pieces together.
Adhesives used as a substitute for a properly made mechanical connection are generally considered a sign of poor craftsmanship. However, adhesives have a legitimate place in healthy connectivity i.e. epoxies and cyanoacrylates (anaerobic, hardens without air, will not fill gaps for too much oxygen).
Cleaning for Adhesives
1. Abrade surface
2. Pickle if metal
3. Rinse in water
4. Wipe with solvent
5. Warm to drive off solvent
This is an ancient technique, moist sand is tightly pressed around a model, which is then removed, leaving a mold cavity to be filled with molten metal. Sand must be sieved, the fineness of grains will determine the amount of detail on the final casting.
Sprues hold a model in its correct position while making the mold, they also provide a passageway for the escape of the melting wax and allow entry for the molten metal.
Lost Wax Process
The process was developed in ancient Egypt
1. A model of combustible material
2. Model is mounted to a wax sprue
3. Sprue is mounted into the base of a flask
4. Plaster like material is mixed and heated to flash
5. Dry or (burnout) plasters in kiln, melts wax model
6. While model is still warm, molten metal is poured into mold
7. After cooling, mold is quenched in water and broken from around casting
The ability to harden and temper steel gives the horologist the ability to create or modify tools and components as different operatives required.