Maintenance

Q: What grease do I use on camera O-rings?

A: There are two basic configurations for O-ring seals; the `Piston' seal, and the `Gasket', or compression seal. In the former, one part of the assembly slides into the other, while in the latter, the O-ring is squashed by a lid. The back doors of Nikonos and Motormarine cameras have piston seals. The back doors of most SLR housings have gasket seals. The O-ring grease is not a sealant; it is a lubricant which enables piston seals to be assembled without damage. Consequently, gasket seals do not need grease, although a light coating may help to preserve the rubber and may assist in cleaning. If grease is required, the type used is very important. In the past, camera O-rings were nearly always made from Nitrile-Butadiene Rubber (NBR), usually black, and the appropriate lubricant is either petroleum gel (i.e., Vaseline, or Nikonos Grease), or preferably Silicone grease (e.g., Molycote 111). Nowadays, Silicone O-rings are common. These are often coloured, and can be recognised by their textural similarity to silicone diving masks. Petroleum gel can be used on some silicones, but silicone grease will cause the material to swell and fail in service. The correct lubricant for silicone rubber is fluorosilicone grease (e.g., Molycote FS1292).

It is also important to distinguish between user seals (like the back door and the battery lid) and control shaft seals. User seals and static seals need only to be greased before assembly, but control shafts need to be packed with lubricant. If you simply grease a control shaft seal, it will soon dry out and fail through abrasion.

Q: How often does camera kit need to be serviced?

A: Immediately before and immediately after every dive. It is the user's responsibility to clean O-ring grooves, clean, check, and grease O-rings, check all functions, and so on; and then wash the equipment and de-mount all junctions between dissimilar metals afterwards (to prevent corrosion). No amount of technician service can compensate for bad working practices, and most accessory items will function for years without technical intervention if correctly looked after.

Periodic technical service is of benefit in the case of underwater stills and video housings. An annual service is advisable if the camera has moderate use. It is also sensible to arrange for equipment to be serviced before embarking on an expensive diving holiday or expedition, and to allow several weeks for the sourcing of any spare parts which may be needed.

Q: What should I use to clean plastic?

A: Washing-up liquid (dish soap) and water is a good bet. If you use solvents, you really need to know what you're doing. Alcohol can cause acrylics (Perspex, Plexiglass) to shatter spontaneously. Acetone, MEK and chlorinated solvents, all usually do plenty of surface damage. Light Petrol (cigarette lighter fluid) is usually OK on acrylics, ABS, PVC, Nylon and polycarbonate (Lexan), but always try somewhere unimportant first.

Q: Can I fix things with superglue?

A: In the UK a few years ago, a hideously misleading TV advertising campaign led the general public to believe that just about anything could be repaired with cyanoacrylate adhesive. One of the consequences was that people started pouring superglue all over their underwater photographic equipment, presumably on the basis that something useful might happen. It rarely did, and quite a few service customers went away with a hefty invoice bearing the words 'complete replacement underwater housing' (or words to that effect) or a cheaper alternative document saying 'beyond economic repair'.

Cyanoacrylate adhesive does have many applications, but if your knowledge of materials science is limited, the best advice is: don't put cyanoacrylate adhesive anywhere near your camera equipment. It forms a lousy bond with, and does irreparable damage to, most of the plastics commonly used. Epoxy resins don't usually work either, but at least they are not so destructive. Attempts to repair cracked housings are rarely successful, but you can stick things back on to the inside or outside. You can weld ABS and UPVC using plumber's solvent-weld adhesive. You can weld Polycarbonate (Lexan) with 1,2-dichloroethane, but it's a black art. You can weld acrylics with special adhesives obtainable from industrial plastics suppliers. You can weld polystyrene with polystyrene cement supplied by model shops and toy shops (Americans call it 'polystyrene dope'). You should read the health and safety information on all adhesives and solvents before using them.