By Dr Mike Burchett

‘Standard’ hard hat diver’s helmets are highly collectable, and the older, more sort after models of past manufacturers now command high prices. Therefore it would seem sensible to look after a helmet that has accumulated a life time of character along the way. However, all too often, helmets are acquired at great expense, only to have their character and surface patinas destroyed by over-correction and polishing, for no other reason than aesthetic looks. The root of this problem lies somewhere in the past. Our eyes are readily drawn towards a gleaming steam engine with freshly painted livery, or a motor vehicle brought back to perfect working condition. Traditionally, metal wares including copper, brass and silver were constantly cleaned to a mirror finish, regardless of the damage being done to the surfaces. However, attitudes are slowly changing and a more thoughtful, conservative approach is being adopted towards the preservation of helmets and other associated diving apparatus. In today’s market, a valuable piece of antique wooden furniture would not be systematically over-restored, altered or stripped of the patina to satisfy current aesthetic trends. To do so would be to destroy its character, history and value. If a historical artefact is placed in the care of a museum, the main priority is to stabilize and conserve the item for the future, and aesthetic considerations are not given top priority. It is hoped that a similar more enlightened approach will be adopted by owners of historical diving apparatus in the future.

Having said all this, few people would wish to display a filthy helmet that has cost a good deal of money. This article is not about restoration, but focuses on cleaning a diver’s helmets in a more appropriate way for display. It also assumes the helmet is in a reasonably stable condition and it will not be used for historical diving purposes.
Although this article is written in good faith, the outcome of any cleaning work undertaken on a helmet is the responsibility of the individual concerned. However, I hope the article is useful for those who do wish to adopt a more enlightened approach to the care and cleaning of their diving apparatus. It is worthwhile reading around the subject, as opinions differ among conservators as to the most appropriate treatments, which are constantly evolving and being improved.

Luckily, old diver’s helmets are relatively simple pieces of apparatus that are ruggedly constructed to withstand use, abuse and the underwater environment. They are mostly made from various ‘non-ferrous’ materials including copper (Cu), tin (Sn), zinc (Zn), Admiralty bronze (‘G1’), Naval bronze (‘gunmetal’), Admiralty brass (‘CZ111’), Naval brass (tinned brass: ‘CZ112’) and soft solder (tin/lead mix). Nominally, brass is an alloy of copper with zinc, whereas bronze is an alloy of copper with tin. The words ‘brass’ and ‘bronze’ are often used interchangeably, which causes confusion when examining old diving equipment. The chosen cleaning materials must be suitable for all these metals and their alloys, as they are generally found together in the construction of a helmet. The cleaning materials must not damage any other soft materials used in the helmet, for example, natural rubber seals and leather gaskets of the neck ring and face plate.

Avoid: stripping, polishing, lacquering, painting and re-plating surfaces wherever possible.
Avoid: using chemicals to artificially age helmets as it will never look correct and it can seriously damage the metal of a helmet. Allow a helmet to age naturally.
Avoid: removing factory applied lacquers and paints. Instead, clean stabilize and wax them.
Avoid: using household detergents and cleaners, liquid metal polishes (the residues are hard to remove and causes further tarnishing), car polishing compounds, ammonia, vinegar, lemon juice, acids, salt, abrasive powders, abrasive papers and cloths, wire wool, mineral oils and stiff wire brushes (especially steel ones). Basically, anything that is harsh, reacts with, or scratches a metal surface.
Avoid: over-wetting areas with water, but instead use a sponge, cloth, or absorbent cotton wool moistened with water. Flooding the internal helmet communication system is not a good idea.
Do: be patient and do not rush tasks. If in doubt stop, think and if necessary consult an expert. Each helmet will have its own individual problems.
Do: try a treatment on scrap material before trying it out on the real thing. A successful outcome may depend upon trial, error and practice in the first instant. It is sometimes difficult to reverse treatments, therefore proceed with caution.
Do: undertake cleaning tasks by hand (not with the aid of machinery and power tools). There is then less likelihood of accidental damage or over doing a treatment.
Do: use solvents that can safely be used to clean metals, which include white spirits (cheap and available), acetone (smelly but useful), ethanol (vodka will do) and clear methanol.
Do: use clean tap water which is normally fine for most rinsing purposes. Suitable cleaning agents include ‘conservation grade detergent’ (‘cgd’ such as ‘Vulpex’). Always use ‘cgd’ sparingly and rinse well afterwards. A cheaper, more readily available alternative is mild hypoallergenic liquid skin care soap which is unperfumed and undyed.
Do: use cleaning compounds that are formulated for conservation work. If it is necessary to use a cleaning compound, a little ‘Pre-lim’ is useful (see addresses). The best method of protecting cleaned surfaces is with ‘conservation’ wax. One of the leading conservation waxes for use on virtually any material is ‘Renaissance’ Wax. This blended microcrystalline wax was formulated by the British Museum and is now in use worldwide for many applications. Once dry, it is hard enough to prevent finger marks appearing. Although it is relatively expensive, a little does go a long way, and it lasts for years. It can be readily removed with white spirits (thus reversible), and the helmet will only require an occasional dusting and waxing every few years. However, do read the instructions for the use and application of these products.
Do: support a helmet properly during treatments. A simple padded surface (e.g. thick foam cushion wrapped in a towel) is useful and helps prevent the helmet from rolling around, or even worse, dropping onto the floor.
Do work in a well ventilated area (especially with acetone); use disposable gloves (nitrile rubber gloves last longer with solvents) and when necessary, a disposable mask. Gloves also prevent finger contamination which can cause tarnish during the finishing stages of de-greasing and waxing.
Useful cleaning tools and consumables include natural bristle brushes; old soft tooth brushes; plastic picks; wooden spills (lolly sticks); bamboo picks; soft plastic scrapers; a metal scriber; a strong straight needle; hair drier (use warm to cool to speed up drying); lint-free soft cloths and rags; soft plastic scouring pads; cotton wool and cotton buds; small sponges; ‘WD 40’ light oil or easing oil (for those hard to undo fittings); silicone grease and petroleum jelly (pure Vaseline).

1. First check the helmet for signs of factory lacquering (some continental helmets are lacquered). A lacquered coating in good condition should be left in place and preserved. The same is true for original factory applied paintwork (for example on ‘Miller-Dunn’ shallow water helmets).
2. Disassemble some helmet parts (e.g. valves, spitcock etc.). Fittings and components that are readily removed will not be in the way, and are more easily cleaned off the helmet. Carefully remove the leather gaskets from the neck ring and face plate, and keep them flat for later cleaning. Take disassembly photos if you are unsure how the re-assembly sequence may go. It is also a good record of progress before, during and after helmet treatments.
3. Always try each stage of the cleaning process or a treatment on a test area, or test piece to see if it is suitable for the material (preferably in an area that will not be seen). Remember there is often little chance of reversing a treatment; therefore proceed with care and caution.
4. Clean the helmet and parts with water and a damp sponge inside and out (do not flood). If the helmet is heavily soiled with dirt, use a little ‘conservation grade detergent’ (‘cgd’). Threads and hard-to-reach corners may require the use of a soft bristle brush (old tooth brush). Once the helmet is clean, damp rinse surfaces to thoroughly remove any remaining detergent residues.
5. Clean the helmet again, but this time using a solvent (e.g. white spirits) which will remove any grease or wax deposits. If the face plate and neck ring channels have accumulated deposits of green ‘verdigriz’ where the leather gaskets are seated, it should be thoroughly cleaned. Sometimes it may be necessary to scrape the channels with a sharpened bamboo spill, followed by light scrubbing with a soft plastic scouring pad and solvent.
6. (Optional step). If the helmet has achieved the desired look, then proceed to the waxing stage. However, if the helmet and parts require a more thorough clean, then proceed with the cleaning compound. Use a little ‘Pre-lim’ cleaning compound and a soft application cloth. Apply with a light circular rubbing motion in small areas, and work into adjacent areas for an even tone. Complete the major copper areas first, then the fittings afterwards. Once the residue is dry, lightly buff the surfaces with a clean soft cloth. (Follow the ‘Pre-lim’ instructions).
7. If step 6 has been undertaken, then re-clean the helmet with solvent to remove any remaining cleaning compound residues. A warm to cool hair drier may be used to thoroughly dry the helmet.
8. Corselet stud threads (and any other threads) can be lightly buffed with a soft bronze brush. This will also remove any fine particles of trapped dirt that remain.
9. Leave the helmet and parts to stand for a few hours. Apply a thin coating of ‘conservation’ wax (e.g. ‘Renaissance’ Wax) to all surfaces within 24 hours of solvent cleaning. A soft bristle brush is ideal for those hard-to-reach areas, otherwise use a soft cloth for application. Leave for the recommended time before buffing. It may be necessary to repeat the waxing for a second time (read the instructions).
10. Leather gaskets will often have accumulations of in-grained oil and dirt, but may be cleaned by the following procedure if they are in good condition. While keeping the gasket flat, thoroughly clean both sides using a 1:1 mix of water and alcohol (e.g. acetone, or ethanol vodka and water). A short soaking may be required. With the leather in a damp (half dry) state, rub in a minimum amount of ‘neatsfoot’ oil with the thumb and forefinger. Remove any excess by blotting with a dry tissue. Place the leather gasket back into position. Olive oil and coconut oil are ‘not’ good choices, as they are prone to oxidisation, causing discoloration and hardening of leather.
11. Re-assemble all parts of the helmet. Smear a little ‘silicone grease’ or ‘petroleum jelly’ on internal threads before assembly, but take care not to spread it onto the newly waxed surfaces.

Helmet display is the choice for the individual. However, helmets that do not readily stand by themselves need some form of support. A slatted wooden stand (natural hard wood is best) will not only look presentable, but allows some ventilation under the helmet. A cotton towel placed between the stand and helmet will prevent chemicals from the wood affecting the corselet surface.

For long term storage, use bags made of breathable woven polyester (e.g. ‘tyvek’) or a well washed, large white, cotton pillow case. Do not seal helmets in polythene (e.g. bubble wrap) for long periods as this may seal in moisture, causing corrosion problems later on. Humidity changes with the seasons and location, which may cause condensation to form on a metal surface. Therefore store the covered helmet in a dry place.

Picreator Enterprises Ltd. (email: Suppliers of materials for professional restoration and conservation, and manufacturers of ‘Renaissance Wax’.
An in-depth report on the “CARE AND CLEANING OF DIVER’S HELMETS AND SOME OTHER DIVING APPARATUS” can be obtained from the author.

Robert Burchett (graphics and photos).