The first posting is on lacquering brass. There are two more. The next is on lacquering dials, although some members of this list have substitute techniques for dials. I lacquer because dials were either lacquered or shellaced originally, admittedly a somewhat Luddite philosophy. The third posting is on applying shellac as an historic alternative to lacquering.
Preparation of metal prior to lacquering is fundamental to good metal coating. I do not think I have written much on that subject. Suffice it to say brass should be chemically clean as well as bright. This means it should be "dry polished" with chalk, feldspar or even flour and either a brush or soft cloth after polishing and final cleaning; before lacquer is applied. Otherwise, lacquer is being applied to a film still on the actual metal, and the finish will not last very long. I have clocks come back to me for service that I lacquered the following way over thirty five years ago, and there is no need to remove the lacquer and replace it. It has stood up through more than one cleaning. May 31, 1996 On applying lacquer to brass:
If you contemplate a lot of lacquering, you would do well to buy a quart (if available) or a gallon of "uncut" metal lacquer for spraying. You can reduce it with lacquer thinner, then add about 10% of retarder to make brushing lacquer. You would need to thin the lacquer to a watery consistency for dipping, and I would use little, if any, retarder for that purpose. All of these combinations of thinner, retarder, and lacquer are based on experience and have to be adjusted for specific conditions. Since nitro-cellulose lacquer is increasingly hard to find in any form, you may have to use acrylic lacquer. I am unaware of any real problems resulting from its use, and I am told it is generally applied the same way as nitro-c. I have no objection to the use of spray bombs except their cost in a high volume operation. Because I use so much lacquer, it is more economical for me to use and maintain spray equipment. The cost is obviated to some extent by the fact I have compressed air in use for many purposes throughout my shop. As to dipping plates, I would advise against it mainly because there is so much work involved in preparing a plate for submersion, or in removing unwanted lacquer in bearing holes, screw holes, etc., after dipping. A variety of parts may be safely dipped in thin lacquer, but some will require secondary efforts to remove unwanted lacquer. Wheels, for example, can be dipped if care is taken not to submerge the pinion, and pivots will have to be cleaned after dipping. The Connecticut clock factories dipped brass parts, but this was done before wheels were rivetted to arbors, plates and bridges were drilled or broached, dials and glass were attached to dial pans and bezels, etc. I suspect British and European manufacturers followed similar procedures in production of "rolled brass" movements. Manufacturers such as Howard also lacquered plates and other parts, but until late in their history, lacquer was applied with a brush. Much later, selective spraying and dipping were adopted. I spray nearly all the brass on rolled brass movements. I do it immediately after cleaning and polishing of the parts. I then proceed to polish the pivots, thereby removing any lacquer on them. I examine lantern pinions and remove lacquer as necessary with a pipe cleaner and acetone. When I repair the movement I peg bearing holes, dipping the pegwood in acetone if there is an accumulation of lacquer there. I put "gun patches," soft 3" squares of flannel sold for cleaning gun barrels, under the plates when I ream for bushings. Only when dramatic repairs are required do I wait to lacquer the involved parts until the work is done.
There is a reason for this beyond cosmetic value. I lacquer for the same reasons it was done in the factories. First, I am able to work without concern for the effects of handling unprotected brass. I don't have to wear gloves to avoid fingerprints. And I don't like to see finger prints on clock movements. The second reason: old, oxidized brass has a somewhat dull surface, particularly around pivot holes, which invites migration of oil. By lacquering, there stands a better chance the oil will form a meniscus around the pivot, the arbor shoulder, and in the oil sink, when lacquer is present. Thus the clock stays oiled longer.
All of this advice has to be tempered with historic knowledge and good judgement. I lacquer the plates of grandfather movements and French clocks even though neither were usually lacquered originally. I don't lacquer their trainwheels, but I lacquer winding drums and French barrels. I don't lacquer the plates of marine chronometers. I do polish the plates and the oil sinks to a mirror finish. I lacquer factory made clocks because factories lacquered them.
Nearly all lacquer is applied with the spray gun described in my comments on dial lacquering. As much as possible, parts are arrayed flat for spraying, or, as indicated, hung on wires. On some high-grade movements which will be displayed, I lacquer train wheels, and in many such instances I use a brush in order to assure that I don't apply lacquer where it is not wanted. The small amount of lacquer which finds its way to the working surfaces of wheel teeth will generally "burnish" off the faces if the train is allowed to run free for a minute or so. I, like the factory engineers before me, have never found residual lacquer there to be a source of trouble in gear trains.
There is considerably more to be said about the use and application of lacquer, the length of this reply not-with-standing. This should be sufficient for now. Text: 810 words Jcl
October 17, 1995 Lacquering dials: Since early alchemists discovered how to make silver ni- trate, convert it to silver chloride, and to precipitate it onto "base" metal, artisans have mechanically plated decorative piec- es. They did it both for effect, and to give the appearance that a dial, piece of jewelry, flatware, tea urn, etc., was other than it really was. Silvering was adopted as yet another means of coloring metal for purposes of decoration and expression. The practice became so wide-spread that it was acceptable, became an art form, and enjoyed the same approval as veneer on wood. Until modern times, when such techniques as vacuum metalizing allowed technicians to make "gold" bottle caps out of plastic, metal coloring was dominated by methods of oxidizing, or preventing oxidization of surfaces through combination with vari- ous chemicals or compounds. The plot thickens when we contem- plate electro-plating, widely used after 1860.
While all of the above over simplifies the history of metal coloring, one fact remains constant. Where unwanted oxidization, usually recognized as tarnish, could occur, craftsmen sought and devised ways to protect their products from the most recognizable source of tarnish: air. Thus they coated their work. Normally, I am willing to bet, a workman produced something looking a cer- tain way with the hope that it could be kept looking that way. I do.
Through the limited sources of information I have seen, I know of several basic coatings used by craftsmen. They included wiping surfaces with animal fat and, particularly in Mediterra- nean areas, vegetable oil in the form of olive oil. Both of these substances harden eventually, and produce a kind of var- nish. As technology evolved, resins were derived which offered more lasting protection. By the middle ages, when wood finishing by more methods than oil finishing developed, compounds leading to shellac evolved. Shellac became the metal finisher's coating of choice even into this century.
The Germans developed nitro-cellulose lacquer in the last half of the nineteenth century. Eventually it replaced shellac, particularly in industry. That does not mean, however, that shellac is not still a good finish for both wood and metal in certain circumstances. I still use it, especially as a restora- tion procedure on both wood and metal, where authenticity is a consideration.
Getting back to silvering dials, if I have not lost you with the history lesson, silvered dials ought to be lacquered. Silver will tarnish in the presence of a hard boiled egg, given the opportunity. It will definitely tarnish in the polluted slurry we inhale as air. In the face of those observations, I will tell you how I treat silvered dials.
After I have prepared, filled and silvered the subject dial, I dry it thoroughly with compressed air, then I give it time to "adjust" to room temperature. Incidentally, I try to avoid doing dials in humid weather. Next, on critical jobs especially, I wipe the dial gently with a clean soft cloth into which I have shaken very fine chalk, (five micron marble dust), in order to abrade off any residual film which might remain from the rinsing process which is a part of silvering. I remove the chalk with a blast of low pressure compressed air, about thirty pounds, so there will be no rapid cooling and condensation.
Now I am ready to spray the dial, and what I spray on it becomes the critical concern. I still use nitro-cellulose lac- quer. I obtain it from the Sherwin-Williams Company where it is marketed as OPEX CLEAR LACQUER T82-C12. There are probably other equal (not comparable) products on the market, but I am not aware of them. Over thirty five years ago I bought the same product, with the same label, and I thinned it almost four to one for lacquering all clock parts. I paid eight dollars a gallon for it. Now, I pay over forty dollars a gallon, and I thin it less than one to one, or fifty-fifty. Safe to say, the product is being phased out, and I will have to find an alternative.
Until the replacement compound and procedure is discovered, I will continue as follows. To prepare the lacquer, under cur- rent conditions, measure equal parts lacquer and thinner into a container, then add 10% of lacquer retarder. Thinners and re- tarders for acrylic lacquer will work. Thus, for example, to one quart of lacquer and thinner (16 oz. each) add a generous 3 oz. of retarder. Use a larger than one quart container, or do your own arithmetic. Shake all of this together and give it ten or fifteen minutes to go into solution. Thinner and retarder can be bought from auto parts and body shop suppliers.
I have to say all of this is arbitrary instruction, and it is subject to variation based on experience. Arrogant as it seems for me to say it, these are general rules, and they should be varied and adjusted according to conditions and experience. It would take pages to delineate every variable. Experiment to learn.
Next comes the question of how to apply the lacquer to a silvered dial. I spray it. I apply one, two, and sometimes three coats to a dial. Years ago I made a sprayer from a throat spray. It is operated by use of a "chuck" from a dentist's of- fice. My sprayer is essentially something between an air brush and an ordinary spray gun. The fact is, either of those extremes will work.
With an air brush, the system must be used for maximum vol- ume of compound: lacquer. The ordinary spray gun must be adjusted for large volume of lacquer at the lowest volume of air before the gun spits or drips. Normally, apply the lacquer by trigger- ing the sprayer on and off while making passes. Starting at the bottom, with the gun spraying at about a 20 degree angle off vertical, go from left to right, move the gun to cover the next width of its pattern of spray and go right to left, etc. On, spray, off, move up. On, spray, off, move up. It becomes a rhythm. Sorry, folks, but at some point I have to cop out: prac- tice and experience become the final teacher. (And I am still learning.)
Someone in our group brought up the question of how to pre- vent dissolution and flow of the filler used in the engraved parts of the dial. With spraying this is usually not a problem unless the first of two or three coats of lacquer is too thin a compound or is applied to thickly. Especially the first coat should be applied thinly, not too thin or watery a substance, and it should be allowed to dry a long time: an hour or so, so that it becomes a barrier to subsequent coats of lacquer.
Acetone, or variants of it, which are the basis of lacquer thinner, is a fairly universal solvent. It will dissolve paint, shellac ( the main ingredient of most dial filling compounds,) varnish, many plastics, and a long list of other substances. Thus, if lacquer applied over dial filler is not too wet, it will soften the filler, but not enough to make it try to go into solu- tion with the lacquer coating to produce the undesirable feath- ered effect sometimes seen on lacquered dials.
Lacquer should be thin enough to prevent "orange peel" from the air used to spray it. It should be thick enough so that it doesn't run or flow into a mass or "sag" on a reasonably level horizontal surface. Dials, and other parts being sprayed for finish should be rested on stands or paper so that they are as close to level as possible. This allows for the easiest kind of lacquer (or paint) spraying. One cannot tip a car to spray it, but that is another subject entirely. The more retarder used in the lacquer, the slower it will dry, but the more it will gloss. Less retarder: faster drying with less gloss. Sometimes the most desirable finish comes from a flat to dull surface. After the bulk of lacquer has been ap- plied, this effect can be achieved by using excessive amounts of air and indirect spraying of lacquer so that a mist or "overspray" dulls a nearly dry glossy surface. There are other "tricks" to spraying, many of which I am ignorant.
Lacquer can be applied with a soft brush. Commercially sold brushing lacquer is generally the same lacquer being sprayed, but with more retarder to slow drying long enough for brush marks to flow out. For brushing on dials, with filler especially, it is probably wise to reduce the amount of thinner somewhat, and in- crease the amount of retarder. This gives the compound less tendency to dissolve the shellac filler before it begins to hard- en, but still leaves opportunity for the brush marks to flow away and blend as the lacquer hardens. There are many variables to this subject which could be brought to bear, including substitutes for nitro-cellulose lac- quer. I will leave those matters for a later discussion, or better, from those with more modern or different experience than mine. Lengthy as this text is, it should not scare anyone away from trying to lacquer dials in particular, or metal in general. I will say that I consider protective coating one of the most important operations performed in my shop. Good luck! Jcl
To Apply Shellac to Metal
Based on a question from David Smith, Auckland, New Zealand (See attached) 4/19/96
Greetings, David. I can report on my experience using shellac, but I don't have scientific answers to your questions. I do not know what is the process, but white, or clear shellac is bleached and refined more than orange shellac so that it has a more neutral appearance than orange shellac on either wood or metal. Much of my knowledge of shellac comes from a late friend who was a highly skilled cabinetmaker. He always dissolved flake orange shellac, which he usually applied with a rag. He never prepared more shellac than he expected to use in a few days. He was also VERY particular that the alcohol he used was fresh.
Both he and I have always used "denatured" alcohol bought in small quantities because alcohol draws water right out of the atmosphere. I have to confess that I don't know the difference between ethanol and methanol; the "denatured" product I use specifies that it is ethyl alcohol. Another can says it contains both. Shellac is adversely effected by water. Once moisture gets into the solution as it will over time, shellac should be discarded. That may be the reason you are getting clouding. Otherwise, I would guess there is some foreign substance in the shellac flakes, possibly from inadequate preparation. The worse aspect of moisture in shellac is that it will almost never dry. I have a clock of my own which I refinished with old shellac. It took over a year for the finish to really harden. Good shellac can be sanded within half an hour of application!
For metal, I actually buy very small quantities of prepared white shellac, rather than dissolving it myself. It is usually sold as "three pound cut," meaning it was made from three pounds of shellac to one gallon of alcohol. It should be thinned a little more. This too is a sign of the times since prepared shellac used to be sold as four pound cut.
Normally I apply shellac to metal by spraying. It can as easily be applied with a soft "lacquer" brush, and probably with one of those disposable sponge brushes. I have never tried one. Where I use it on metal, I generally apply two thin coats by spray, or one only, somewhat thicker, by brush. There will be slight brush marks, and I allow them deliberately, in order to produce the same effect found on old shellac to metal finishes.
Some cylindrical pieces are best shellacked by allowing them to revolve slowly in a back-geared lathe. This way a heavy application of thin shellac can run around the metal so that brush marks flow out but the substance does not sag or collect at the bottom of the piece as it is drying. (Same for lacquer.)
I do not heat the metal first. That would make shellac (or lacquer) dry too quickly. I apply it at room temperature. After it is dry to touch, the coated pieces can be warmed to accelerate complete hardening, but shellac reacts unfavorably to too much heat.
I have restored several early scientific instruments which had to be refinished because they had been handled in spots so that the original shellac was worn through. Surrounding the worn areas were sections with the original finish in tact, and the graining or other finish on the metal beneath looked perfect. When the old shellac was removed, the metal beneath was actually frosted or etched. I have always presumed that some of the early shellacs were impure, and there may have been acid present which activated from time to time, under humid conditions. A guess on my part.
Shellac will not gloss quite as much as retarded lacquer, but the difference is slight, in my experience. When applied to wood, shellac, lacquer, and varnish are all usually sanded between coats, then the last coat can be rubbed to a polish. I am not aware that these procedures are used for clear metal coating. I have never found the need.
There are numerous antique receipts for brass and metal "varnish." They are all fundamentally shellac dissolved in alcohol, with various colorings or supplemental resins added. Except where the most historically authentic finish is required, any additional coloring of shellac can best be done with alcohol soluble stains and dyes used by cabinetmakers. Mentioned in an earlier posting, "dragon's blood," and "annatto," sometimes spelled "annotto" in old books, but not in the dictionary, were common colorings.
For most clear metal coating, lacquer is the most convenient and practical form of protection. The effect of shellac is pleasing, and is suitable as a way to produce an authentic appearance to pieces which will be protectively displayed, and not subject to frequent handling. Jcl
Copyright by John C. Losch, Holliston, Mass. , reprodoced on Horology - The Index with permission of the author.
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