Description
This article is from the Antique Radios
And Phonographs FAQ, by Hank van Cleef vancleef@netcom with
numerous contributions by others.
64 Cosmetic and cabinet finish
This section discusses some of the methods that can be used to clean and
restore items in acoustic phonos antique radios, and other items. While
the internal construction of phonos may be quite different than that of
electronic devices, many of the cleaning issues are quite similar.
Almost any old device requires a fairly standard cleanup involving
removal of dust and dirt, internally as well as externally. The first
step in restoring an harmonium (reed organ) or a piano, as well as a
phonograph, music box, or radio, is to clean the item thoroughly, inside
and out, and assess its condition. Very often, all that is needed is a
good vacuuming, with the help of some small paintbrushes to loosen dirt,
and a soap-and-water cleanup. Clockwork mechanisms, small electric
motor mechanisms, and electric phono turntable, wire recorder, and
similar mechanical transport mechanism generally need to have old
"petrified" lubricants cleaned off, and reassembly with new lubricants.
Cabinet restoration depends on the method of cabinet construction and
finishing. Items built in the 19th and early 20th centuries generally
had wood "furniture" cases, finished with a shellac process. The
introduction of synthetic varnishes in the 1920's meant a rapid change
to use of synthetics for wood finishes, and shellac finish on a home
entertainment device becomes rare through the 1925-40 period. Post WWII
wood finishes are most commonly one of the urethane synthetics.
Plastics that could be formed by casting and injection molding processes
became available at the end of WW I, and many home entertainment devices
made in the 1920's have visible parts made of "Bakelite," a phenolic
resin with an inert filler that can be injection molded. By 1940, there
were a variety of thermoplastic (i.e., melts when heated) and
thermosetting (i.e., cures under heat and does not remelt) resins were
commonly used in construction of molded radio cabinets, knobs, and
decorative trim items. Many of the plastics used in the later pre-WW II
period were not stable over long periods. Ultraviolet from strong
sunlight and heat above human body temperature would accelerate
distortion and discoloring, for which there generally is no repair other
than replacement of the affected part. Items in good condition should
be cleaned up and positioned where they will not be subjected to strong
sunlight or heat.
Various metals are used both in internal construction and in cabinetry.
Painted steel plates and cabinets are commonly found. Also stamped
brass decorative parts. One very common process was to use steel and to
electroplate it with a brass finish. Die cast white metal parts are
commonly found. The zinc alloys used in the 1910-35 period produced
excellent parts, but are subject to aging and corrosion breakdown.
Typically, they will become larger, then become extremely brittle and
crumble. Once again, the only "repair" solution is replacement of the
affected part. There is a long-standing myth that white metal parts were
made of "floor sweepings" and scrap, and the term "pot metal" is
sometimes used in the US to denote the material. This is not accurate.
Zinc precision die casting technology uses specific alloys and
processes, and produces excellent results. Some manufacturers used
die-cast or sand-cast aluminum alloys after the mid-1920's. These
should not be confused with zinc alloys. Die casting processes for both
zinc and aluminum produce high dimensional accuracy, but require
creation of an expensive metal mold set, so are generally associated
with high-volume parts. The tooling required for sand casting is much
simpler and less expensive, but the as-cast parts require machining of
critical dimensions.
This is a very cursory overview of materials and processes, and the
reader who wishes more information should search out and study some of
the literature written for engineers and crafts people who work with
these technologies. In particular, "Machinery's Handbook" and (in the
US) the SAE Handbook (Society of Automobile Engineers) have extensive
information on metals and manufacturing processes.
Your FAQ editor has some strong feelings about some of the techniques
for cleaning and restoration that have been discussed on various
newsgroups. There is no question that many restorable items have been
ruined beyond repair by use of inappropriate chemicals and cleaning
methodologies. Beyond this there are considerations of "kitchen
chemistry." Almost any solvent or process has safety considerations to
consider. And almost any solvent or process will damage something in a
device. You may want to use it over here on this metal part, but if you
get it on that plastic part or electronic component, in may destroy it.
Additionally, there are issues of fire hazards, fumes, violent reactions
with other chemicals, and safe storage to consider. Know your products,
and know your processes. A kitchen is a place for food preparation, not
chemistry experiments or industrial processes. Be very careful to keep
solvents where they cannot contaminate foods or anything used for food
preparation. Store chemicals separate from food items, and away from
the inquiring hands of small children. Also keep in mind that many of
the preparations sold in grocery stores for kitchen cleaning purposes
are, in reality, very strong chemicals, and may have very little
information on the chemical content or processes. When writing this, I
checked a can of Dow brand oven cleaner. It acknowledges 4% sodium
hydroxide as an active ingredient, and gives a litany of safety
precautions in use. This stuff is more violent than most of the
industrial cleaning processes I've used. Many of the spray can cleaning
products are very easy to use----just spray them on your valuable
antique and watch it dissolve before your very eyes. Remember that
these are proprietary products, and while the labels may disclose a few
"active ingredients," it is often not all that is in there that will
wreak havoc. There is a steady stream of notes in the antique groups
from people who tried a spray can kitchen product and discovered, too
late, that it took markings, finishes, etc. off along with the dirt.
There are two manufacturers who make chemical products specifically for
use around electronics equipment. Caig Laboratories makes "DeOxit,"
which is considered by many people to be about the best contact cleaner
around. They make a number of other chemical products for various
electronics uses, and provide good and specific application and use
notes for their products. GC Electronics, formerly General Cement, make
a variety of products for various uses. These include a good electronic
coil dope, a chemical wire insulation stripper for stripping the enamel
from magnet wire, and a variety of cleaning products and adhesives.
One "easy cleaning" method that gets tried regularly is use of a
household dishwasher to clean things. Don't do it. Almost all
dishwashers use high temperatures in their washing cycle, and the
detergents used are a strong caustic solution. They may wash dishes
well, but for other cleaning, have almost all the attributes and
drawbacks of a hot caustic tank (see "lye," below) with few of the
virtues. I've had the unpleasant experience of spending a day with
precision machine tools reworking the castings in an automotive power
steering pump that were put through a good household dishwasher.
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