Buffing and Polishing Guide Tutorial Procedures for Silver or Gold Metal Jewelry

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Taogem:
Chapter eight from Sharr Choate's Creative Gold and Silversmithing - jewelry - decorative metalcraft

Buffing and Polishing Procedures Are The final steps required for finishing all metal articles. Buffing removes sanding marks and smooths out the metal in preparation for the final polishing. Any pits, scratches, or minute file or sanding marks overlooked when buffing are only accented by the polishing step. Polishing adds only color, brightness, and luster to the metal surface.

Buffing

Buffing removes from the surface a thin film of metal equal to the depth of the scratch or mark, and therefore excessive buffing will only wear away precious metal, including any square corners that might be a part of the design.
Whenever possible, parts of any metal craft assembly should be buffed before soldering so that all areas receive at least one buffing before the final stages of finishing. Areas which in the final stages may be inaccessible to buffing wheels require special buffing operations, and if a portion of the buffing is completed before soldering, then the total buffing time will be minimal.Buffing Speeds

All buffing and polishing methods use power equipment, except thrumming (string buffing) and stick buffing (flat wooden or plastic stats covered with felt, leather, etc.) Definite motor speeds are required for buffing and polishing. Definite motor speeds are required for buffing and polishing. The important factor to consider for the most satisfactory job is surface feet per minute (sfpm). Motor speeds should be capable of producing at least 8000 sfpm on the buffing wheel, and at least 5000 sfpm on the polishing wheel. Speeds rated in rpm are used for rotating surfaces that do not change their diameter dimensions, such as shafts, spindles, pulleys, etc. Buffing and polishing wheels which wear to a smaller size through use, are calculated in surface feet per minute.
A motor rotating at 2400 rpm will turn an 8″ buffing wheel 5025 sfpm, but as the wheel wears down to 7.5″, the same motor speed produces only 4387 sfpm on the buffing wheel. Polishing plates (fig 82) should be purchased with a two speed arrangement of 1725 and 3450 rpm, or a single speed motor can be adapted for two speeds by installing a two step pulley on the motor, and a single pulley on a polishing arbor. The motor and arbor setup, both equipped with 2″ pulleys, will produce the basic motor speed. Identical sizes of any dimension, even of 5″ diameter, will still produce the basic motor speed, but the perimeter of the wheel will be traveling a greater number of surface feet per minute. Weigh a 2″ pulley on the arbor, the speed of this wheel will increase approximately 280 rpm with each 1/4″ increase in motor pulley diameter.
By checking the chart, pulley combinations and wheels with specified diameters, rpm and sfpm can be obtained.
Surface feet per minute is the distance traveled by the outer rim or working surface of a wheel rotating at X number of rpm. Surface feet per minute for an 8″ diameter wheel rotating at 5040 rpm can be determined by the following example:

The wheel diameter (8 inches) is multiplied by pie (3.1416) to obtain its circumference (25.133 or approximately 25 1/8 inches). The circumference is multiplied by the arbor pulley rpm (5040) to obtain the number of inches (126,670 inches) traveled by the outer rim of the wheel in one minute. The sum is divided by 12 to obtain the number of surface feet per minute traveled by the rim (10,555 inches).

This method of calculating sfpm can be used for any size wheel providing the rpm of the motor or motor and arbor combination is known.
Many rpm and sfpm combinations can be worked out with various motor speeds and pulley arrangements. A two step pulley with the largest pulley diameter of 4 inches, and the smallest 2 1/4 inch diameter will turn a 2 inch arbor pulley 4165 rpm and 2565 rpm respectively, and an 8 inch wheel 8723 sfpm and 5372 sfpm respectively, while using a basic speed of 1725.





Dust Collectors and Hood Dust Collectors, shallow metal pans with hoods and cutouts to fit over motor shafts, serve as a catchall for buffing dust, and the metal article if it should suddenly be snatched from the operators hands. Hoods, often equipped with a small incandescent bulb for greater visibility when buffing, can be attached to vacuum cleaning units. This eliminates much of the buffing and polishing dust that flies around the work area to be inhaled by the operator.



Buffing Wheels

The various buffs, wheels, laps, and compounds for buffing and polishing are as numerous as their uses and are described here not in order of preference, but as general information.
Cotton flannel buffs with rows of stitching to make the wheel sturdy and fairly rigid are used for general buffing work. Muslin buffs, unstitched and attached at the center only, are usually reserved for polishing steps. As the buffs wear, the threads are cut so that the buffing edge can be used more effectively. The wheels can be trimmed with an ordinary kitchen grater held against the rotating wheel to shape the buffing surface to a new flat or tapered edge. Cotton (muslin buffs if preferred) can be charged with fine emery grit which is excellent when used to produce a scratch or satin finish.
Separate buffs and wheels must be used for each compound used on gold and for each compound on all other metals collectively. The wheels should be clearly marked for their particular use near the center with a color code for identification. Wheels that have been inadvertently charged with a different compound should either be trimmed to clean the working surface, washed, and dried, or discarded. Substitute wheels can be made by tearing discarded fabrics such as cotton prints, old sheets, etc., into 6 inch squares. The center of each square is marked, and a small slit made so that the square can be placed on a threaded mandrel. (Tapered mandrels should not be used here) The fabric squares are placed on the mandrel until the bundle is approximately 3/4 to one inch thick, and the flange nut added and tightened. With the motor switched on, the squares are trimmed to circular shape with a kitchen grater or sharp knife held parallel to the fabric edges. Cotton flannel and muslin buffs are used on textured and overlay surfaces. Felt buffs are used on plain flat surfaces.
Midget buffs, wheels, and brushes 7/8 to one inch diameter are used with the same compounds as their larger counterparts. Knife edge buffs are used for smoothing bezels and any areas where a flat buff may cut a groove in the surface of the metal on a different plane. Cotton string buffs in different sizes and shapes are adaptable to any buffing and polishing job.Goblet, tapered cone, and cylinderical types with rounded flat or pointed ends are permanently attached to a mandrel that fits into the polishing lathe chuck or the Jacobs chuck attachment on a buffing and polishing arbor and are used with any buffing compound.



Brushes

Hard or soft bristle hog hair or nylon fibers are used in bristle brushes. These are used with grease base compounds for satin finishes. They are especially preferred when buffing chased, repousse, engraved surfaces, and for square bezels to preserve the squared corners perfectly. They are also effective for buffing around prongs, mountings, clasps, and other fastenings and findings, besides working well on filigree, florentined, and scroll work articles. The bristles carry the compound down into the undercuts and hard to get to areas before the upper surfaces are worn smooth or rounded over.
A different bristle brush wheel must be used with each buffing compound. Bobbing compound is the preferred material for buffing when using this type of wheel.

Bristle Hand Brushes

Brushes with the same type bristles as used in the buffing wheels are used primarily with bobbing compound for cleaning and hand buffing filigree and florentined work.



Metal Scratch Brush Wheels

Steel, nickel, monel metal, and brass wire scratch brushes are used dry for cleaning metals, and for effecting a scratch finish on the metal. Brass wheels produce a much softer finish, but are not used on silver as they leave a yellowish deposit on the metal. The wheels should be reversed on the shaft occasionally to keep the bristles from leaning too much in one direction.

Very little pressure is exerted on the wheel so that the wire ends will not be burnished over. If this should occur the wheel is useless. The brushes should be operated at the slower speed of approximately 600 to 1200 rpm. If desired, pumice and water can be used on the wheels to produce a finer matte finish.



Leather Wheels

Stitched leather wheels charged with fine grits or Tripoli buffing compound are used for buffing smooth flat surfaces. The wheels are also available in the small sizes 1/2 to 2 inches diameter.



Rubber Bonded Abrasive Wheels

Finer grit abrasive bonded in hard rubber is used to produce a satin finish when operated at medium speeds of 1500 to 2240 rpm. Higher speeds will put a light polish on the metal and also cut a groove quickly with very little pressure.



Tapered Ring Buffs

Tapered wood buffs covered with a thin layer of cotton or felt or tapered felt cones are used in conjunction with flat wheel buffs for ring finishing. Any buffing compound is used with this combination. The tapered buff finishes the inner surfaces of the ring sides, and the face of the wheel finishes the outer surfaces, except the pronged stone setting which is buffed with a bristle brush wheel.
Rings should not be run all the way up the buff when the motor is running, for the buff will grab the ring and injure the operator.



Wood Laps

Small wood laps with flat or knife edges are used on a tapered spindle. Abrasives, bobbing and Tiipoli compounds are used to buff sections where a sharp defined corner or area is to be retained.

Buffing Compounds

Tripoli compound is the most generally used buffing material and bobbing compound follows in close order. They work well on most metals and types of surfaces, but the preferred use of each has been given for the craftsman’s choice. Tripoli is generally used on gold, silver and nickel silver and worked with buffs, brushes, and laps. Bobbing compound is used on any metal with a brush or lap, but not on buffs. White diamond compound is for general use on copper, brass, bronze, and aluminum, and worked on a buff, brush, or lap. Fine every grit mixed with white vaseline (never yellow) is used for satin finishes on any metal. Pumice and water paste is used for a satin finish on silver because it gives a higher luster than those produced otherwise. The work is done with a bristle brush or wooden lap.
When the metal section or article is ready for buffing it is scrubbed with warm soapy water, rinsed, and then placed in pickling solution which is brought to a near boiling point to remove any oxides and any remaining flux if soldering has been done. It is then rinsed again in running water and dried..
The buffing wheels are charged with a scant amount of compound, not only to keep the shop clean, but because buffing compounds leave a black deposit on the metal if an over abundance of compound is used. The compounds are applied to the wheels as they are running slowly. This is accomplished by turning on the motor and then switching it off before it has had a chance to gain momentum. At the switch off moment the compound is applied to the wheel, acting as a brake to slow it down. This procedure prevents an excess of material from loading the wheel, thus hindering the buffing action. It also leaves less compound to be thrown onto the workbench or into the dust cover. The corners of the wheel are charged with compound so that they too will buff the metal as it is worked across the face of the wheel.
Tripoli compound will adhere more readily to the buffing wheel if the stick is dipped in kerosene before coating the wheel. Overloaded wheels can be cleaned by holding a short length of hacksaw blade at a 90 degree angle to the wheel face as it rotates. This will slightly decrease the diameter of the wheel. The wheel can also be cleaned with the grater used for truing wheels.

Polishing

Polishing, like buffing, is done primarily with power equipment, and with various shapes and types of wheels, brushes, buffs, etc., but with different compounds.Polishing Speeds

Surface feet per minute requirements for polishing wheels are as important to polishing as to buffing. Polishing requires less speed than buffing, therefore motor rpm, pulley arrangements, and polishing wheel sizes should be computed so that the polishing wheel runs as close as possible to 5000 rpm.
Special buffs are used for each polishing compound, and extreme cleanliness is important. The polishing buffs should be stored when not in use in plastic bags to prevent contamination with buffing or sanding materials. Wheels are color coded, cleaned, and shaped in the same manner mentioned for buffing wheels, brushes, etc., that follow are for general information and are not listed in order of preference.

Muslin Buffs

The most common polishing wheel is the muslin buff, loosely stitched or center attached only and used with rouge polishing compound. The loose flexible folds of the fabric permit the polishing compound to adhere readily to the inner folds so that the fabric quickly reaches all portions of any textured or formed surface. These buffs are also available in the small sizes, 7/8 to 2 inches diameter.

Flannel Buffs

Used in the same manner as muslin polishing buffs.

Felt Buffs

Hard wheels used with all rouges produce the best polish on smooth flat surfaces. Knife edge buffs are used to polish sharply defined corners without rounding them. Various shapes of felt buffs such as tapered cones, ball, cylinder, and goblet are used with various compounds for a high luster finish on the inside surfaces of metal objects.

Leather (chamois, buckskin) Wheels

Unstitched leather polishing wheels, similar to muslin buffs, are used with the different rouges for fine finishing on textured, formed, and smooth surfaces.

Bristle Brushes

Fine bristle brushes are used with pumice and water paste to polish filigree and florentined textures and any other complicated or intricately detailed surface.

Wood Laps

Small wood laps are used with all polishing compounds to polish square and sharply defined corners. They can also be used for polishing flat enameled surfaces.



Stick Buffs

Stick buffs are wooden slats covered with felt, chamois, or buckskin. They are charged with the polishing compounds and used to hand rub the surfaces to a high polish.

Rouge Polishing Cloth

A soft flannel like fabric impregnated with a rouge compound is used for hand polishing. This cloth is usually sold with an uncharged fabric section used for the polishing after the surfaces have been rubbed with the rouge charged portion.

Polishing Compounds

Rouge polishing compound in bars or peel away tubes is the most generality used polishing compound. Various rouges, identifiable by colors, are used with specific metals. For instance, red rouge is used on gold, silver, and copper but not on burnished surfaces, creating a discoloration, and will be impossible to remove in minute compressed areas. It is not objectionable if a light film of the compound remains in cuts and grooves on chased and engraved surfaces; however, if a dark color is actually desired, it is best to use an oxidizing solution or some other type of surface coloring agent.
Brown rouge is used on softer metals, such as pewter and lead. White rouge is best for polishing platinum and white gold. Platinum rouge is used primarily for these two metals. Green and yellow rouge create a high luster on stainless steel.
Any rouge should be used sparingly. Excessive amounts applied to the wheel will pile up on the metal surface, causing these areas to remain dull when the compound is scrubbed away; also, excessive pressure or overly slow surface speed on the wheel will cause a pileup of rouge and the same blotchy finish.
Pumic and water paste gives a rich luster to silver. This paste can be applied with a brush, felt buff, or with the finger and by hand rubbing.
A combination of whiting and water is used dry to highlight oxidized surfaces. The dry powder is picked up with a finger dampened with water and then rubbed on the metal surface. It can also be used with a bristle brush if mixed with water to make a paste; however, this is usually only used on filigree or florentined pieces.

Chrome Oxide

Chrome oxide is a compound that comes in either a powder mixed with water to a paste, or in a bar as a grease base compound. It is usually used to polish certain gemstones, but it can be used on a flannel buff to give a mirror finish to nickel silver.

Tin Oxide

Tin Oxide is another useful lapidary polishing material. It is mixed with water to form a paste and is used only after other polishing compounds have been meticulously scrubbed from the metal surface. Tin oxide preserves the high polish, especially on tarnish prone metals, and adds an even greater luster to the metal than does a regular polishing agent. It should never be used in place of the regular polishing compounds required for specific metals.

Linde A

Linde A is a compound used in the same manner described for tin oxide, but it should be used in a hand rubbing operation rather than with power equipment.
Polishing compounds are scrubbed away in the same manner as described for buffing compounds. All traces of the compounds must be removed or they will eventually discolor and tarnish the metals. After scrubbing the polished metal and rinsing it in running water, the article is placed in a box of hardwood sawdust such as maple, birch, mahogany (not Philippine) or boxwood to avoid its streaking or spotting as the metal dries. (Other woods contain soluble matter and resins that can tarnish metals and therefore are not recommended.)
The metal article is removed from the sawdust with cotton gloved hands to prevent leaving any fingerprints on the surface.

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