Surprisingly for a medium which relies on undulations as small as 25nm to hold information (this dimension being about 1⁄20th the wavelength of light) there exists a paucity of scientific literature on best practice in storage, handling and cleaning of gramophone (phonograph) records to ensure their cleanliness and dimensional stability and integrity over time.
Granted, a YouTube search (April 2018) for "record cleaning" produced nearly 1.5 million hits, but, if the first 50 or so are anything to go by (frankly, a tedious task), it is extremely rare that videos such as these offer any significant advice on the care of records. No video of the sampled fifty offered serious, empirical measurements of the difference in sound quality pre- and post-cleaning, or between one method and another. None included microscopy, and none considered the chemistry or any long-term effects of the techniques demonstrated.
For a truly thorough study of record care, we have to go back a long way, to the end of the nineteen-fifties, to a report by a team working for the US Library of Congress (LoC) under a research grant from the Rockefeller Foundation1. Happily this report is late enough that PVC-PVA copolymer records (LPs and singles) were included in the study as well as acetates and shellac records.
Another oft-cited reference to record care2 is really more journalistic than scientific and, despite originating an industry in the manufacture of record cleaning machines, offers no real evidence for the methods proposed beyond the assertion that, "It does [work], to a degree that sets a new standard of listening pleasure".
More modern references on advice (largely to archivists) on the best methods for the storage, handling and cleaning of records, the most recent being published in May 2015 3, 5, indicate that the advice derived from Pickett and Lemcoe nearly 60 years ago, still represents the solid-core of our understanding of the best ways to keep records, and keep enjoying them.
This is all the more remarkable when you consider that Pickett and Lemcoe's long-term recommendations for vinyl records were made a scare ten years after the invention of the medium. It is greatly to their credit that their wide understanding of chemistry, of materials science and even the life sciences6 and to their thorough experimental work that they were able to give advice which has stood the test of time. Their eighty-page work is offered in as brief a way as possible on this page as well as some more modern advice that they could not have forseen (see references).
Note that this page does not include information of the effect of the stylus upon the groove of a record. That is covered here.
PVC degrades chemically when it is exposed to heat and light. The process begins with the liberation of hydrogen chloride at faults in the PVC molecules. This stripping of HCl allows adjacent molecules to cross-link (or form valence bonds between the polymer chains) and this results in the embrittlement of the plastic and warping. This process is termed condensation. The resulting production of hydrogen chloride gas is a catalyst for further dehydrochlorination within the plastic, so the hydrogen chloride gas must be absorbed. This is the role of the stabiliser - often a compound of lead (Pb) - which is added to the plastic copolymer from which the record is compression moulded.
Happily, in long term studies of the degradation of records1, it appears that sufficient effective stabiliser remains in a plastic disc to protect it for a very long time. Nevertheless, keeping all records away from (especially short-wavelength) light sources and at a reasonably constant temperature below 70°F (21° C) will substantially prolong their life.
Condensation affects shellac resin too, but a collection of shellac discs will often be affected differently by condensation because of the degree of cure of the shellac. As the LoC report concludes, it is useless to attempt to undertake any quantitative study of the properties of new or aged shellac discs because there is no such thing as a "typical" shellac formulation. Nevertheless, light and heat play a role in the condensation of shellac as they do in PVC, so the same advice pertaining to PVC records applies to shellacs too.
One very undesirable property of PVC-PVA copolymer records is their tendency to warp to a degree that they become unplayable when they are allowed to become warm. Anyone who has left a vinyl record in a car on a hot day will recognise this! Shellac records are largely more resistant. It is believed that unresolved stresses within the polymer of PVC caused by moulding and rapidly cooling are resolved when the record is re-heated to anywhere close to its softening temperature and it is this which causes the warping. Some modern products are available to repair warped records, all of which rely on heat and pressure. The degree to which this technique is sucessful depends on the "cure" (the degree of cross-linking) in the polymer. As Pickett and Lemcoe say, the best way to avoid this is simply never to let a record get hot because recovery is never certain.
Records of all types should always be stored in a strictly vertical position, so that one record does not lean against another under a gravity load. Substantial pressure should not exist between the records, so shelves must not be over-filled and, ideally the shelving should be divided every 10 to 20 discs, so that any gravity loading (other than that strictly in the plane of the disc) is resolved by the dividers and not against further records. Records of different diameters should not be stored together: they should be arranged in separate compartments of the shelving.
Shellac discs are generally susceptible to supporting fungal growth and the fungi's excretions can badly damage the lands and grooves of these records. PVC discs are not especially vunerable to fungi as these ubiquitous organisms find little to feed upon in PVC. However, fingerprints serve as a good culture-medium for fungi and vinyl records are susceptible to etching from fungal actvity. So the importance of keeping records clean is paramount for all types. Just as all records should not be stored in too warm an environment, they should not be stored somewhere damp either as this encourages fungal activity.
Unlike the plastic itself, record jacket materials are especially good at supporting fungal growth, so attention should be given to separating records from their jackets, in the case of LPs, preferably in a smooth high-density polyethylene liner sleeves made especially for the purpose. Serious collectors might consider the Library of Congress' approach which is to store records separately from their commercial packaging; the separated records being protected by a special, sealed jacket3.
With all types of disc, the grooved surfaces must never be handled; either support the middle and edge of the disc, or just the edges. Discs must be inserted into and removed from their packages without touching the grooves and avoid (as much as possible) sliding contact between packaging material and grooved surface.
Records should be both played and stored clean. A dirty record is a noisy record. And the disc is much more likely to be harmed both by physical deformation due to dirt both when it is played, and when it is stored, if it is not scrupulously clean. Furthermore, any dirt is more likely to support fungal growth during storage.
Record contamination can be divided into various categories2:
Naturally, these contaminants aren't isolated and usually exist together in a rather unpleasant cocktail.
If a record (LP or shellac) is badly contaminated, there is little option but to wet-clean it well away from the turntable7. There are several record-cleaning machines which dispense the cleaning liquid and, with vacuum suction, draw the dirty liquid off; all variously based on Wilson's original device described in reference 2 (right).
More modern devices employ ultrasonic cleaning in which a ultrasonic transducer excites a bath of cleaning liquid to create many millions of small voids (tiny bubbles of vacuum) in a process called cavitation. These bubbles implode with enormous energy. A record, lowered into the bath and perhaps rotated by a motor, will be cleaned as the microscopic shock-waves from the implosion of the bubbles scrub the dirt and contaminants from its surface.8.
All these record cleaning machines (RCMs) are useful if you have a large collection and need to clean many records. But hand-cleaning is effective too if performed carefully4, 5.
Pickett and Lemcoe's advice to the LoC1 when faced with a highly contaminated disc was, wash the disc in a lukewarm, mild detergent solution, rinse with distilled water and air-dry. To which we should add: care needs to be taken not to wet the record label (or, at least, keep this to a minimum). And do not wet clean Edison Diamond discs or novelty discs made of card etc. in this way5.
Once the record has been thoroughly wet-cleaned, it should not require drastic cleaning again (unless there is some disaster in storage). All that is required is to blow any dust off the record surface with a photographic lens puffer and then wipe an appropriate solution with lint-free material or a synthetic velvet over the surface; following the groove contour.
Pickett and Lemcoe recommended that the following should be applied to the playing surface of the record:
Prior to playback or packaging: a sparingly applied detergent solution with an applicator of sheared acetate velvet fibres.
During playback: a sparingly applied ethylene glycol solution with a brush and mohair applicator pad.
Both these remedies were available to the authors as contemporary commercial products. (The Lektrostat Record Cleaning Kit of Dexter Chemical Corp. and the ESL Dust Bug respectively.) The authors go on to say,
Other systems of dust control and cleaning (such as spray on antistatic compounds, treated cloths, dampened synthetic sponge, and radioactive air ionization) were tried but did not prove as satisfactory as did these techniques.
No doubt there will be some that gasp at the suggestion of ethylene glycol on the roller of the Dust Bug. Yet, uninhibited ethylene glycol is successful at attracting a surface film of moisture and thus preventing electrostatic charge accumulation on the surface. It is still widely employed (and its cousin, propylene glycol) in many commercial record cleaning solutions. Today, the recommendation would probably be to use a very weak solution of a neutral detergent incorporating nonionic surfactants (see below). Or use a contemporary version of the Watts Dust Bug with conductive carbon-fibre brush to bleed electrostatic charge away from the surface. Or, possibly, to skip this step altogether.
For all their fastidiousness, Pickett and Lemcoe do not discuss the best type of detergent for use in record cleaning. Given that commercial synthetic detergent were only introduced into the United States in 1946, this may simply reflect the then state of the technology of detergents.
Today, there exists a widely discussed conjecture amongst record collectors that domestic dish-soap (washing-up liquid), like Dawn in the USA or Fairy Liquid in the UK, are not the most suitable detergents for record cleaning.
Largely consisting of powerful anionic surfactants, these household products do nothing to neutralise the negative electrical charge present on the PVC disc, and any residue after rinsing may contribute to it. These products also contain salts and oils (the latter as perfumes) which may also remain on the playing surface after rinsing.
There seems to be no systematic evidence for these suspicions (at least, any that's published). However, in a world where non-charged (neutral) detergents exist which exclude perfumes and salts, the only real reason for continuing the use of domestic detergent products for record cleaning is inertia! One such neutral detergent is Tergitol made by the Dow Chemical Company. The Library of Congress now employ Tergitol for record cleaning diluted to 0.05 percent in deionized water5.
Being rinsable at the concentrations recommended for record cleaning, these detergents fulfil perhaps the golden rule in record care and preservation which is: don't apply anything to the playing surface of a record which might prove difficult to remove afterwards. Which brings us to lubricants.........
Regardless of how smooth a surface may appear to the eye, at a microscopic level, every surface is formed of a series of peaks (called asperities). When we try to move one solid surface against another, at an atomic level, the asperities in the surfaces grind against one another, alternately welding to one another by forming chemical bonds, and shearing as the weld is overcome by the force doing the moving. This process wastes energy and wears out the materials in the phenomenon we call friction. Just as with any two solid surfaces moving relative to one another, there exists friction between stylus and record groove.
When the stylus is placed on a turning record, the downforce of the styus will initally hold the asperities of the two surfaces together, stretching the elastomer bearing which holds the cantilever. This will continue until there's enough energy stored in the springiness in the bearing to overcome the coefficient of static friction13. At that point, the stylus will move until the energy in the spring is exhausted and the stylus will, once again, come to rest. This process repeats again and again, the movement of the stylus relative to the vinyl record being a series of snags and jerks, a type of friction which tribologists (those scientisits who study friction) call stick-slip. The net-effect of these stick-slip interactions accounts for the kinetic friction13.
The discontinuous (stick-slip) movement of the styus in the groove is the origin of the noise-floor of reproduction from PVC records. Naturally, the surface asperities in the vinyl are random, so the stick-slip is not a regular buzz but is random too. This random movement, modified by the bass-boost of the RIAA characteristic gives rise to the background noise in reproduction which is sometimes called vinyl roar.
The coefficient of kinetic friction for a stylus in an LP groove varies according to the manufacture of the record and type of stylus but it is always in the region of 0.3. Lest we imagine that this friction is negligible, it's worth remembering that the coefficient of kinetic friction of standard motor-car brake-pads against the steel brake-disc is in the range of 0.35 to 0.4. The impression of a stylus gliding gently along in a groove is a misapprehension, engineered by massive platters and high-torque motors. In reality, the stylus is being yanked reluctantly through the groove.
"The impression of a stylus gliding gently along in a groove is a misapprehension, engineered by massive platters and high-torque motors. In reality, the stylus is being yanked reluctantly through the groove."
Lubrication is used in all manner of engineering applications where surfaces move relative to one another to reduce friction and transfer some of the heat away from the junction to the lubricant. In some situations, the lubricant may by squeezed into the gaps between the solids so that they remain entirely separate (think of a barge sliding along a canal, separated from the river bed by the lubricating water). In others, the lubricant may create a boundary film which partially separates the two surfaces and helps relieve the worst of the stick-slip friction. At the pressures involved at the stylus/vinyl interface, film lubrication isn't possible, but boundary lubrication is feasible.
It seems a reasonable hypothesis that lubrication might reduce the sliding friction between stylus and record groove. Boundary lubricants are effective up to their melting point and, given that the softening range of a record is a modest 100°C or so, it would seem that suitable unguents would be readily available. Surely, lubrication might, not only, help lower playback noise, but might help too in the preservation of the precious information in the groove walls by reducing the damage done by the stylus?
Given these two enormously worthwhile aims, you would think that audio-widget manufacturers would have been clamouring to be involved in this interesting area. And yet, there seems to be a paucity of research which would seem to exploit a technique which is so commonplace as to be virtually universal in other disciplines where friction is known to be a problem.
There are a few commercial lubrication products for records. One product is based on polydimethylsiloxone; the material used to buff-up car interiors and make the dashboard look more shiny. Another is based on Dupont's perfluoropolyether (PFPE) based oils and greases and known as Krytox. Used in hostile environments, Krytox oils and greases are chemically inert, thermally stable, and have a very low coefficient of friction, so they seem ideal. Another still is based on a dry lubricant for the space industry.
However, none of these substances may be removed easily (or indeed at all without resorting to strong solvents). So none has gained universal support, or the support of archivists, despite having loyal followings.
Even for new records, and for records which have been previously deep-cleaned (in an RCM), we recommend a that a record-cleaning fluid is used to remove any oils, air-borne spores and mycelial fragments and other contaminates immediately prior to making the needle-drop.
One such is Phædrus Audio's FORMULE (and FORMULE 2 for shellac discs). These fluids are designed to put particles into solution so that they may be captured by the material of the cloth or velvet pad and dissolve any grease and oil9.
FORMULE (1 and 2) also contain a trace amount of an antimicrobial agent which remains effective against many household fungi even at very low concentrations. If a gentle dose of this fluid is employed the disc surface will completely dry in about 2 minutes. Playing should be postponed until the record is really dry.
Do not be tempted to rotate the turtable as the disc is drying. A turning record creates a vortex-like suction causing ambent air (with all it attendant hazzards) to be drawn down to the surface of the disc2.
Cleaning after playing is wise too and we do it. But, if this is done, the disc must be allowed to dry completely before returning it to its sleeve or the risk of fungal activity during storage is greatly intensified.
We do not use a stylus-groove lubricant.
Static electrical charges on plastic records were a problem (even an obsession) for early hi-fi buffs and, if internet forums are anything to go by, they seem to have resurfaced as a problem for more recent enthusiasts of the medium's revival.
The surface resistivity of a pure PVC-PVA copolymer record is very high; greater than 1 × 1013Ω. As the newly manufactured record is removed from the metal mould, having undergone great pressure and heat cycling, the plastic material acquires a substantial triboelectric negative charge10. This initial charge is probably greater than any subsequent handling and playing will generate later in the record's life.
It was widely believed during the 1950s that this static charge was the responsible for the pops and clicks which beset vinyl records. Whether this was due to the deliberate misinformation by some clever marketing type, it's difficult to say. Perhaps the concept was easier to accept to a generation who knew interference on AM radio stations as "static"?
In any case, the truth was more unpleasant, the interference wasn't due to electricity - or, at least, not directly. Rather the pops and clicks were due to the electric charge on the record attracting and retaining all kinds of damaging particles in the grooves of the record. The stylus, on encountering these particles "glued" to the surface by Coulomb's force, was obliged to plough over them or jolt around them; in either case often driving the particle into the soft plastic where it, or the imprint of it, would be held for the lifetime of the disc.
Various approaches to solving or ameliorating this problem were developed during the first ten years of the LP-era; most of which consisted of materials designed to give temporary relief. Many have resurfaced along with interest in "vinyl" records. These consist of wetting-agents or detergents diluted in water or some other carrier and sprayed or wiped over the surface of the record which leave a film of electrically conductive material over the surface. From the perspective of today, the better of these materials gives only very temporary relief from the problem. The worst leave a gummy film which a 1950s stylus tracking at 10g might have been able to plough through, but which today must be cleaned away; sometimes with considerable difficulty. Some record manufacturers applied materials of this sort after pressing too.
Some fantastic inventions were marketed to reduce the static charge on the surface of the LP, the zenith perhaps being a 3M product which encased the radioactive material Polonium 210 in a ceramic bar. Brought close to the record, the α-particles emitted by the Polonium (essentially nuclei of Helium) neutralised the negative static charges (electrons) upon the surface of the plastic. Apparently, it worked very well!11
In the early 1960s RCA's record division commenced a crash-programme14 to solve the issue of static electricity by reducing the surface resistivity of the plastic with the inclusion of additives to the polymer compound. At first, they tried increasing the amount of carbon-black added to the mix. This conductive material was already present as a colouriser in records but in insufficient quantities greatly to affect resistivity. So, it was an obvious idea to increase the concentration of carbon-black. This had the desired effect but, in concentrations sufficient to solve the static charge problem, the roughness of the carbon raised the surface-noise of the disc.
RCA eventually developed a solution which involved the compounding of an quaternary ammonium salt into the copolymer; a noteworthy piece of chemical engineering and one which effectively removed the static problem from PVC records in conditions down to 20% relative humidity. RCA's marketing department came up with the term Miracle Surface for discs manufactured with this new anti-static ingredient. Solutions similar to RCA's gradually became the norm for all manufacturers of PVC compound for records, so that, for children of the sixties and beyond, static was never really an issue with records.
There is some suspicion that new records may be being made without (or with less) static-reducer compound in the rather quaint pursuit of "pure-vinyl". This seems an entirely backwards step. Certainly, internet forums of vinylistas new to the medium seem to be discussing "the static problem" in a way which is reminiscent of 1950s literature12. Perhaps a Polonium 210 α-particle source will, once again, become a "must-have" device for the record shelf?
1. Preservation and Storage of Sound Recordings. Pickett, A.G.; Lemcoe, M.M. (US) Library of Congress Report 1959
2. Record Contamination: Causes and Cure. Wilson P., JAES April 1965 (Curiously, the best parts of Wilson's paper concerns his observations concerning the aerodynamics of the turning turntable and his excellent appendix concerning the static charge on a record and how it resembles the permanent electrophorus of Volta. Yet these observations seem to have had little or no impact on the design of record-players.)
3. Operation of the Recording Laboratory in the Library of Congress Carneal, R.B., Presented to the 35th convention of the AES October 1968
4. Hand washing also has the advantage that a good supply of cleaning solution is available. Some record cleaners (especially the cheaper types) only have a small reservoir. If the fluid is largely water and perhaps a wetting-agent, the fluid is not dissolving contaminants, it's merely putting them into suspension so they may be removed along with the fluid. That process is much less reliable if there is not a substantial amount of liquid and rinsing.
5. ARSC Guide to Audio Preservation ed. Sam Brylawski, Maya Lerman, Robin Pike, Kathlin Smith. The Council on Library and Information Resources Publication 164. May 2015
6. Consider the following from their report. Not many scientists at the end of the 1950s had so thorough an understanding of the ubiquitous role of fungi in life on earth.... and on gramophone records!
The fungi play an indispensable role in the carbon cycle on which life is based by converting the waste products of life into usable compounds and thereby keeping the building blocks of organic materials in circulation. In order to do this efficiently, they have evolved into a very large and heterogeneous group of organisms which attack a tremendous range of organic materials and have an equally wide range of acceptable environments for growth and reproduction. Two of their methods of propagation, by air borne spores and mycelial fragments, are so efficient that the exposed surface of any material in ordinary environments is continually being inoculated by a changing variety of these organisms.
7. There is one alternative which is the subject of many of the record cleaning videos available on YouTube and that is using a wood glue, smeared onto the playing surface to create a continuous, flexible layer which may be peeled off the record (along, it is claimed, with the dirt) when dry. No serious evidence is offered as to the effectiveness of this method compared with the more traditional approaches. Whether or not the polymer "skin" is completely removed from the record, or if some remains in the grooves remains an open question. Neither do any of the videos sampled discuss the effect upon the copolymer from such an operation. Given that the glue in question is based on polyvinyl acetate (PVA) in an emulsion in water, there are some grounds for optimism that the chemsitry may not be incompatible with the vinyl chloride-acetate copolymer used to make the record. However, most glues of this type are sufficiently accidic to etch plastic (pH 3), and they contain a salt (NH4Cl) which probably gets left behind in the groove after cleaning. There's no doubt, however, that this method makes for a good party-trick!
8. An important consideration for the record collector is that medical research (where ultrasonic cleaning is widely used) has shown that air-borne spores and mycelial fragments remain on the objects after ultrasonic cleaning, so this method is not effective against the suppression of fungal action: that needs to come from the choice (and "brew") of the liquid used in the bath. Ultrasonic cleaning is endorsed by the Council on Library and Information Resources (5) as an approved method to clean records. However, sadly, a study of the microscopic effects of this cleaning method on records has never been published.
9. Role of scanning electron beam microscope in disc recording Alexandrovich G. Presented at the 58th Convention of the AES November 1977. (We use a synthetic velvet type cleaner. Scanning electron micropscope images due to the phono-cartridge manufacturer Stanton Magnetics reveal clearly the superiority on the synthetic velvet type cleaner over others. To quote from the paper's concluding section,
To clean dirty records, one has to exert a certain amount of force to remove dirt particles clinging to the surface of the vinyl. From all record cleaning devices, ones with thicker shorter bristles did a much better job of removing debris collected even at the bottom of the groove. ........ Devices using carbon fibers are too soft and if you divide the total force applied to the brush by the number of fibers, each fiber will exert pressure of less than 0.1 mg against the record surface [and] they do not remove nor attract dust like other ungrounded devices with heavier bristles......The action of such brushes is analogous to the moving magnet picking up iron filings and dragging a trail of them behind. Dust picked up electroslatically by the brush is dragged behind in a similar manner.)
10. Regardless of how smooth a surface may appear to the eye, at a microscopic level, every surface is formed of a series of peaks. When two materials touch, they are separated by these peaks which are called surface asperities and these prevent the bulk of the surface atoms of the materials interacting with each other. However, when materials are in intimate contact, as when a hot plastic has been squeezed under great pressure against a metal mould, the surface atoms interact and exchange electrical charges. Under these circumstances, chemical bonds are formed between the surfaces and they are said to adhere to one another.
If these materials are subsequently separated, electrical charge is transferred from one to the other. This charging process is known as the triboelectric effect. As to whether a material gains positive or negative charge in these circumstances is complicated and difficult to predict. The phenomenon has been (and still is!) the subject of much scientific investigation and research has produced various tables known as the triboelectric series. A material towards the bottom of the series, when touched to a material near the top of the series, will acquire a more negative charge. The farther away two materials are from each other on the series, the greater the charge transferred. One example of a the triboelectric series is illustrated right. Note the PVC is near the lowest material in the table.
Incidentally, the term triboelectric literally means electricity by rubbing because it was thought for hundreds of years that it was, for example, the rubbing of amber with rabbit fur that caused the static charge to be generated. It's now understood that the rubbing action is just a special example of a more general effect. Rubbing two materials together breaks down the surface asperities and causes the materials into intimate contact.
11. The Nuclear Products Company of El Monte California still produce a Polonium 210 loaded brush for record and film cleaning.
12. Ironically, as less quaternary ammonium compounds (chemists call them "quats") are added to the plastic in manufacture, so has the market developed for record static reduction liquids to be sprayed, or otherwise applied, to records prior to playing. These products are almost universally based on - quess what - quats!
The resurgence of "the static problem" is as likely due to the widespread abrogation of the lessons learned by the fifties' generation in relation to records and static. Wilson (ref. 2) noted that a conductive record mat solved the problem of surface charge whilst the record was on the player. But the modern trend for cork, felt and even Perspex and glass record-mats abandon this benefit entirely. Quite apart from the odd idea that - in the case of acrylic and glass - a record resting on relatively few surface asperities (and quite likely some particulate contaminates) is a desirable thing!
13. The Coefficient of friction is a dimensionless ratio of the force needed to move one object against another as a ratio of the force pressing them together. If a 1kg object sitting on the floor needs 9.8N of force to get it to move, we say that the coefficient of static friction (μs) is equal to 1 because the same force is required to move it as the force holding it to the floor (in this case, gravity). If it requires 9N to keep the object moving, we say that the coefficient of kinetic friction is (9/9.8), or μk = 0.9. Often the value of kinetic friction is (μk) is lower than the coefficient for static friction (μs).
14. Control of Static Electricity on a Phonograph Record. G. Humfeld JAES October 1962
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