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Watchmakers' Hand Book

Part II,
Page 12


      154. The watch-maker has occasion to employ a few acids and salts. He should never forget the advice already given to keep them away from his work-bench and always to well wash a piece of metal that has been in contact with them

      155. Acids. Nitric Acid, either in a concentrated or dilute form, will dissolve iron, steel, copper, lead, silver, zinc, brass, nickel, mercury, German silver. It does not dissolve tin, but reduces it to a white powder, known as metastannic acid. Hence, if an attempt be made to dissolve bronze which contains tin, this metal is deposited, and the copper and zinc pass into solution.

      Sulphuric Acid will dissolve iron, steel, copper, tin, silver, zinc, brass, nickel, mercury, German silver.

      Aqua regia, a mixture of about 2 parts hydrochloric and 1 part nitric acid, will dissolve all the above-named metals, and in addition, gold and platinum, although separately neither acid will attack these metals.

      Hydrofluoric acid attacks and dissolves all metals, except platinum, lead and silver with violent effervescence. It is also used for etching on glass or enamel. It is usually preserved in gutta-percha bottles, and is of such a dangerous nature that no use should be made of it without a good knowledge of its properties.

      Acids are rarely employed pure by watch-makers; they are diluted with water. Nitric acid of commerce has a density of about 1.4 (38° on Baume's hydrometer). If this density is reduced by addition of water to 1.16 (20° Baume), we obtain the acid most commonly employed. For cleaning metallic surfaces prior to soldering, etc.; for steel, special proportions are found most convenient, which the reader can best determine experimentally for himself, remembering that the action of the acid should neither be too quick or too slow. When once he has ascertained the best proportion, he can always recover it by the aid of the hydrometer.

      156. Salts. Borax serves as a flux in soldering gold, silver, platinum, etc., (131); also for the same purpose in brazing (138); it is met with in crystals or as a powder.

      Sal Ammoniac also called Chloride of ammonium is used for soldering tin, either as a powder or made into a paste, with sweet oil or with water, or mixed with resin.

      Alum dissolved in water may occasionally be used in place of nitric acid for cleaning surfaces that have been soldered; it attacks iron or steel more energetically than copper, zinc, or brass. This fact is often taken advantage of for removing broken screws, etc., from brass plates. All other steel parts are removed and the plate placed in a solution of alum, when the steel screw is gradually eaten away by being converted to rust.

      In 100 parts of cold water, only 9 parts of alum will dissolve, but is the water be boiled, it will take up 75 parts. Its action will then be proportionately more energetic when boiling.


      157 The oil intended for use as a lubricant for watch-work, etc., should be kept away from the light, as otherwise it would be discolored; it is on this account that the bottles containing such oil are frequently covered with black paper. Only the quantity wanted for immediate use should be placed in the oil-cup.

      Two preliminary tests will afford some indication as to the quality of an oil. A thick layer is placed on a small portion of the surface of a glass plate, and side by side, a similar layer of another oil used for comparison, and they are exposed to the air for some time without being touched. The one that is found to be sticky under the finger when the other has dried up will, in all probability, be preferable. The second preliminary test is made on a whetstone; It is usually found that the oil that takes the longest time to thicken is of better quality. Of course these tests will only suffice to afford a rough approximation, and cannot be accepted as conclusive.

      The mode adopted for testing either the acidity or the purity of oil will afford no evidence as to how long it will maintain its fluidity; and very good results have at times been secured by the use of oils that were slightly acid, or from mixtures of oils of two or more qualities.

      Many of the methods recommended for purifying oils are to a great extent illusory, for they cannot impart to the fluid characteristics that are wanting from the beginning. Success depends largely on the skill of the manipulator; and if he is not endowed with the power of judging, mainly by the taste, whether oil satisfies certain prescribed conditions, he can never be certain of the result. Crops differ as regards degree of maturity, etc., from year to year; and the animals from which oils are procured are rarely in the same condition as regards health, age, nourishment, etc.

      Tests made on a whetstone, and on a window-pane, as well as observations made on drops of oil placed in jewel holes, or in oil cups in a metal plate kept for the purpose- some of the drops being exposed to the air, while others are in closed boxes- will afford valuable indications; it is safe to consider an oil bad if, at the end of six or eight days after being placed on a plate of good brass, it shows a marked green tinge- especially so if a clearly defined fringe forms round the drop, or else if the brass itself is discolored.

      After all, the only evidence on which the watch-maker can rely is that which he obtains by experimenting on watches which he keeps to lend to his customers while their own are undergoing repair, and these trials should last for at least a year.

      And there is great variety among the wearers of watches. Some live in constantly varying temperatures, often dusty; many ladies use perfumes; some persons perspire more than others; all these causes influence the oil, and make it alter or evaporate more rapidly in one watch than in another.

      158. To secure the maximum permanency in oil. In the case of very many watch-makers who complain bitterly of the oils they employ, the fault is their own and not that of the oil; for they neglect the most simple precautions, both in purchasing and in using it.

      The following are a few points to which attention should be given:

      Do not buy, from motives of economy, bottles that have lain for years in the shop.

      Keep the oil away from the light, and only take in the oil cup the amount required for immediate use, as stated above.

      Ascertain that the watch-cases close well. If they do not, there will be air currents generated, and the oil will suffer.

      The oil in a cylinder escapement will always deteriorate very rapidly; some watch-makers coat over the inside of the dome-joint and recommend the owner not to open it. By doing so, the oil can be maintained in good condition at the escapement for a long time.

      Lastly, when cleaning a watch, the work should be conscientiously done. This point is very important.

      When the parts are carelessly cleaned with soap, or with impure benzine, they will, after a few months, assume a dull colour, in consequence of a thin layer of the materials used in cleaning having been left on the surface. It has at times been noticed that steel work was preserved from rust through the perspiration of the wearer, after being cleaned by certain fluids. Evidently this was due to a thin coating having been left on the surface of the metal. The conclusion to be drawn is obvious: clean carefully; push the pivots into rather hard pith; finish with soft brush in proper condition, and clear out all pivot-holes with pegwood.

      159. Mixed oils: camporated oils. Good results are frequently obtained by mixing together two different kinds of oil. Thus, American watch oil, which is very fluid and apt to evaporate at the temperature of the pocket, is improved by the addition of a somewhat thicker oil. A mixture of real American oil with the Rodanet oil has been recommended as excellent.

      There are some who advocate the addition of a small quantity of camphor to an oil that is known to be satisfactory, but we cannot answer for it from personal experience.

      160. Sinks. In cleaning, it is important to avoid the gilding in the oil sinks of watches, or the superficial oxide in the sinks of clocks that have been going for a considerable time. For if it be removed, there will be a fresh coating formed in time, and this, too, at the expense of the oil.

      In new time-pieces that are not gilt, it is well worth while polishing the sinks over their entire surface. If not applied too liberally, the oil will then be more likely to remain in contact with the end of the pivot. Moreover, as the surface is smoothed and hardened, and its pores are, as it were, closed by the action of the polisher, the oil will oxidize more slowly. This fact was first pointed out by Robin.

      161. Caution to be observed in applying oil. The precautions to be observed in applying oil will be better considered in Part V. of this work, where we shall describe the method of cleaning and putting a watch together.

      162. Retention of oil on acting surfaces. Since oil is essential in order to diminish friction, and the movement of the bodies to which it is applied tends to drive it from the surfaces of contact, it is important, with a view to its being constantly brought back and maintained in proximity to these surfaces, that they be formed in accordance with certain rules based on the laws of hydrostatics.


      163. Only what is known as rectified alcohol should be used in cleaning parts of watch-work. The copper pan in which it is made to boil should not be too thin. the handle should be so arranged that it can be fixed in the vise, and the lamp held under the pan.

      When, in heating, the alcohol ignites, it is best not to attempt its extinction by blowing; if the pan is held against the under side of the bench, the flame will at once be put out, or this can be effected by merely laying a piece of sheet metal over the pan. A good plan for preventing ignition is to make a lid of wire gauze, which is placed over the pan during the application of heat.

      The substance known as "methylated spirit" is a cheap preparation of alcohol, and of use for burning in a spirit lamp, and for other purposes where alcohol is not required to be pure.


      164. This and other preparations of a similar nature, such as Essence Lemoine, Essence Genevoise, ets., are much used for dissolving clogged oil and other substances of a greasy nature from parts of watches in cleaning.

Submitted by: Samuel Kirk (##)

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