June 7, 2009 at 3:49 pm #1378Gerry O’HaraKeymaster
Several models of radios produced in the 1930’s through 1960’s contain asbestos containing materials (ACMs) in their construction. Asbestos is the generic term for a family of naturally-occurring fibrous minerals. The fibrous nature of the mineral, its inflammability and low-cost made it a popular choice in applications where good thermal insulation and fire resistance were required. Until the health risks were identified with asbestos and various governments acted to ban the substance from general use, it was also used as a filler in many household products ranging from floor and ceiling tiles, through pipe insulation to mastics, and also ubiquitous use in things like brake linings and gaskets. The health risks associated with asbestos are primarily from inhalation of the fibres (even those invisible to the naked eye), which penetrate the lining of the lungs and. over time (usually decades), can cause lung cancer, or under chronic and/or high levels of exposure, other lung diseases, resulting in lung inefficiency, even if cancer does not occur. Asbestos continues to be responsible for the disability and death of many thousands of people – there is plenty of information on the internet about this material and its health risks, eg. https://www.hse.gov.uk/asbestos/dangerous.htm. It is therefore wise to be aware that asbestos products can be present in a radio and, if suspected, take suitable precautions.
In radios, the most common form for asbestos to be present is in the form of an insulating panel between the chassis and the cabinet in both wooden and Bakelite/plastic radios. Such a panel normally consists of a sheet of compressed white asbestos combined with a cement to bind it together, up to a quarter inch in thickness (though often thinner). Similar sheets of asbestos may be present between other heat-generating components, eg, rectifier and output tubes, dropper resistors, power transformer and the cabinet of heat-sensitive components. Occasionally, washers made of asbestos, asbestos gaskets and asbestos sleeving on wiring may be encountered, and watch out for those line cord droppers – these are likely to contain asbestos insulation on the wires within the outer jacket.
Personally I always remove any ACM from my radios, even if it appears to be in intact condition, as I am concerned that leaving asbestos in a radio where it is open to the air you breathe, fibres have the potential to be propelled into the room by the thermal currents created by the radio. Once you identify a suspected ACM during a radio restoration I would advise you to wear a well-fitting dust mask (or preferably a respirator) while removing the item for disposal. If the ACM item is damaged and friable (crumbly) any disturbance of the item can cause release of fibres into the air. A solution of PVA adhesive in water can be applied (by spraying or soaking) and allowed to set before handling to ‘fix’ the loose fibres and mitigate release when handling. Remove the ACM item and seal into a plastic bag for disposal. Then wipe the inside of the cabinet with a dampened cloth to mop-up any loose fibres that may have lodged there over the years (then dispose of the cloth). Asbestos is a classified as a hazardous material for disposal and local regulations for asbestos disposal should therefore be sought and followed.
Ok, so the ACM was in the radio for a purpose and removing it may cause other problems, such as damage to the cabinet or other component in the radio, and even result in a fire hazard – so, what to do? Well, in some cases, such as a line cord dropper, there is probably not much you can do apart from recognizing there is an issue, leaving the asbestos in place and limit disturbance of the item – the risk must be evaluated and, if you decide to retain the radio in your collection, be managed by you.
In cases of the ACM being used as a heat-protecting sheet, glass fibre has similar insulating properties and you can buy small glass-fibre mats designed for plumbers, to prevent heat from blowlamps scorching paintwork etc. These are readily obtainable at low cost from most DIY stores, and are easily to cut to size. I have used these, sometimes with a sheet of aluminum foil glued to the inside of the cabinet as an extra precaution where significant heat is being generated.October 14, 2009 at 4:19 am #1225Gerry O’HaraKeymaster
An update to my notes on the presence of asbestos in vintage radios. I am restoring the power supply/audio output cahssis of GE J-125 12 tube set for the SPARC museum. On finding an open-circuit inter-stage transformer, I opened-up the can containing both the inter-stage and output traasformers. To my horror the can was stuffed full of white asbestos – see the photos below. I quickly donned my half-face respirator and carefully removed the asbestos into a sealable plastic bag for disposal, vacuuming the final few fibers away before wiping all surfaces down with a damp cloth (also disposed of). The transformer assembly was re-built and assembled without the asbestos packing. So why was the asbestos in there? – I can only suppose it was placed in there to absorb vibration – surely the heat-lagging properties would have tended to allow the transformers to over-heat? – so why use it? (mind you, just about everything seemed to have used asbestos in the first half of the twentieth century…a ubiquitous ‘cheap and fearful’ filler).
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