Lacquering Brass Instruments
This page is in response to a request for information about lacquering brass instruments. Brad Close, a local young repairman with very promising skills and attitude, asked me for hints on subject. My first reaction was that I've always felt that lacquer was one of my weak areas. The volume of instruments that I polish and lacquer is quite small and a really good lacquer job takes a lot of practice. My second thought, though is that I can share some of the ways that I have been able to produce good results in a small shop with minimal investment in tools.
First, and very important, all lacquers are toxic before curing; please handle with great care. Always wear rubber gloves and a fresh air respirator or one rated for lacquer fumes. Replace the filters on your respirator often. Epoxy lacquer is even more hazardous to your health that air dry lacquer.
I do recommend getting a very good quality spray gun. You can experiment with a cheap one, but you will find that a really good gun will be a pleasure to use. I used the Binks siphon feed gun pictured to the left for many years with very good results, but Harry Siverly, of the Horn Shop in Fresno told me about how much he likes his Sata gravity feed high volume, low pressure (HVLP) guns and does most of his work with the smaller touch up gun. I got one of these and have been very happily using it for the last 10 years or so.
I don't believe that there is any advantage in applying more than one coat. You don't want a thick coating of lacquer but rather a thin and even one. Hold the instrument using a wooden dowel in such a way that you can rotate it in order to spray evenly and eliminate runs. Spraying technique is only improved with practice and like so many skills in the shop, you will need to get the tools in hand and get to work.
Early in my career, I sprayed many gallons of Nikolas 2105 air dry lacquer, but was always troubled by the lack of durability of this material. I eventually set up to bake epoxy lacquer and used Ferree's "Perma-Lac". This is really tough stuff, but doesn't hold up well to ultraviolet light that is present in sunlight. Both Mark Metzler and Harry Siverly have switched to using Nikolas' epoxy lacquer and swear by its superiority. Harry tells me that it dries more slowly, so lint can be more of a problem. I switched to this product myself and have been having good results.
The third photo to the left shows how simple an oven can be. This is a metal cabinet that is lined with foil surfaced polyurethane foam that is available at building suppliers. The joints fit tightly (fill any gaps with spray foam) and are taped with the foil tape designed to be used with this insulation foam. With the foam on the doors fitting snugly when closed, this cabinet looses surprisingly little heat. An electric hot plate can be used as a heating element as pictured, or you can take one out of an electric oven. A thermostat from a kitchen oven can be used, although with a bit of trial and error, you can get the correct temperature using the hot plate's built in control. You can see the probe from an cooking thermometer hanging over the right door; this works well.
Backing up a step or two, I'm sure that there are questions about preparing an instrument for lacquering. Large shops generally use hot vapor solvent or ultrasound degreasers for the final cleaning of the surface before spraying lacquer, but as with most details in my shop, I don't have the space or work volume to justify these apparatii. I spend a few minutes with each instrument, carefully wiping it down with cotton flannel cloth. 100% cotton seems to be the only cloth other than microfiber that won't scratch your carefully polished surface. I use my fingernails or sharpened wood sticks with the cloth to get into all the tight corners, getting off virtually all traces of polishing compound. With a lot of practice, I have developed my polishing technique to get the instrument highly polished and with minimal compound left behind on the instrument.
It is important to avoid using any sort of silicone lubricants in the shop. Any oil on the polished brass surface will prevent the lacquer from flowing out evenly and silicone is the worst and very difficult to remove completely once it has been transferred to your polished surface by your fingers, rags etc.
Like everything in this business, high quality polishing is a skill that is long to learn. It is easy to over polish an instrument with the coarser compounds, shortening it's lifetime. It takes good judgement to know how far to go in removing metal to improve cosmetics (pits, scratches etc.) without reducing the quality of the instrument. Never use a file to smooth the surface and use the belt sander rarely and judiciously. I don't use the belt sander on refinishing jobs, only new parts. When necessary, I tear off pieces of worn out sanding belt and sand by hand. It is a far better practice to learn how to remove dents rather than removing metal to hide them.
Many great instruments have been ruined for the sake of fooling the customer into thinking that the instrument has been "renewed".
With the finer compounds (almost always jeweler's rouge), it takes a bit of time experimenting to find how the treatment of the wheels and application to the surface effects the results. Rake these wheels fairly often. Be sure to keep the coarser wheels separated from those with red rouge that you use for the final color buffing. As a general rule, apply the polishing compound to the wheel often, it only takes a few seconds for it to start loosing its effectiveness and the work will progress more quickly by using more compound.
Pay attention to how the work is effected by the pressure and angle of the buff against brace flanges and tubing joints. Some of this is counter-intuitive in that closer work is achieved on the leading side of the buff rather than the middle or trailing side. Often, this is where too much metal is removed in an attempt to remove rough metal or solder near these connections.
Think ahead during the earlier work processes leading up to polishing. Polish the sub-assemblies (bell, mouthpipe, valve section etc.) before mounting them and learn to make a thorough and secure solder joint with the excess solder outside, where it is easy to clean up with scraper, rag and buff.
Once again, I've gotten long winded on this topic, now get to work!