Adrian Legg puts his hands together and asks for some heavenly protection while the paint is flying about. Read on for some home truths about the risks of guitar spraying.

WHEN YOU consider all the horrendous things you can do to a guitar with vicious implements, it might come as a surprise to realise that the most hazardous is probably painting it.

Much depends on precisely how you transfer the paint from can to instrument, of course, but during my stint in the industry, I was periodically involuntarily stoned simply from brush and drip touch-ups and crack repairs, as well as forever getting rashes on my hands from paint and glue.

The big, airy room I had there had previously been a spray shop, but the shrinking company had ripped out the air system and vented booth in the interests of economy. Any spraying would have brought down the wrath of the factories inspectorate and ended in prosecution.

Let's say right at the start that a good quality finish really requires a properly equipped professional spray shop. Anything less is likely to produce a sub-standard job in a poisonous, explosive atmosphere.

Melvyn Hiscock runs through a few options in his book "Make Your Own Electric Guitar", and he, too, has had some decent results with car spray cans. I did a Tele several different colours years ago, and given a few difficult bits, was quite pleased. As the contents of the can reduce and the nozzle gunges up, you get a few blobs and splatters landing on the work, but nothing that can't be cut back and polished.

Spraying from too far away can result in the paint drying en route and landing on the guitar as a suede effect; spraying too close gives splatters and runs, and a badly uneven build-up.

Before you start squirting this seemingly innocuous stuff around, get yourself some rubber gloves and a respirator mask suitable for spraying. A Roebuck C121W is not bad, but watch that the edges do fit against your face properly. Ask a good finish supplier for advice.

WIND FACTOR

Do not squirt your can about in the house — take it to a shed or somewhere similar, open the windows and door, douse naked lights, bare electric fires etc, and organise a large fan to blow the excess spray out quickly. You'll find that used in the open air, a mere puff of wind can blow the spray away from the work as well as depositing bluebottles and grass seed on the wet surface. Most cans are so fast drying that there is not usually too much of a problem with dust. Bear in mind that faster drying celluloses tend to be brittle, and are thus unsuitable for a flexing acoustic guitar. You'll need four or five average cans to get a reasonably solid finish onto a guitar body, and Melvyn recommends the Spectra brand. I can't remember the name of the stuff I used.

WARNING SIGNS

Before we go further, it may be salutary to look at the rules that govern professional spray shop operations, among them the Highly Flammable Liquids and Liquid Petroleum Gas Regulations 1972 No 917, and the Health and Safety Executive Guidance Note EH9 Spraying of Highly Flammable Liquids. The 1972 regulations, you will thrill to hear, unchained the spirit of enterprise by revoking the 1902 Regulations with respect to the manufacture of felt hats, and apply to "a) all factories, b) all premises, places, processes, operations and works... where any highly flammable liquid is present for the purposes of, or in connection with, any undertaking, trade or business".

A Flammable Liquid is one with a flash-point below 32 deg C (the regulations include a prescribed test in an Abel cup and a temperature controlled water bath for establishing this), and Factory Inspector Mr Taylor at Long Lane put cellulose firmly into this category. In fact, just about every finish I've seen has carried the mandatory flammable notice. EH9 tells us that some solvent vapours may form a toxic hazard at concentrations as low as 200 ppm, becoming flammable or explosive at 10,000 ppm.

That latter figure may seem high until you consider just how much a large spray gun can chuck out very quickly. EH9 also warns against a finish that Stephen Delft used to favour, thus;

"Serious health hazards are associated with the spraying of two pack polyurethane paints and lacquers in which one component (commonly referred to as the hardener or catalyst) contains an isocyanate pre-polymer together with (usually) small amounts of free monomeric isocyanate... [it] can present a serious inhalation hazard not only from isocyanate vapours and finely dispersed aerosol mist droplets containing active isocyanate."

There is another whole leaflet on dangers from isocyanates, but EH9 continues:

"When such two-pack systems are being sprayed, the sprayers and other persons in the vicinity should wear positive-pressure, air-fed respiratory protection. Ideally, spraying should take place in a separate spray room or enclosure, maintained under inward airflow conditions with respect to other adjacent working areas. Extracted fumes from the spray area should be suitably trapped or discharged to atmosphere by means which prevent a re-entry to other occupied areas."

The adverse effects are instant in the respiratory tract, dry throat or coughing followed by possible asthma attacks, and maybe eye trouble, severe chemical conjunctivitis, skin irritation and possible dermatitis.

This is just something to give you the flavour of the job. There are plenty of other warnings such as the rapid possible build up to toxic and explosive levels in small enclosed spaces, skin contact hazards particularly from epoxy based paints, the forbidding by the regulations of the use of iron or metal scrapers for the removal of spray residues, the build-up of residues on fans which can unbalance them and lead to work-hardening and failure of electrical insulation with consequent electrical arcing (think how the internal combustion engine works), heater surfaces whacking up vapour temperature...

Quite clearly, given the unsuitable surroundings that most amateur spraying will occur in, there are problems involved in using a spray gun and an air supply designed for covering areas larger than a guitar body. Apart from the sheer quantity of paint chucked about, a clean dry air supply of at least one cubic foot per minute — preferably two — is required for most decent guns. And assuming that about 35% of the paint won't actually stay on the guitar, a good extractor system or an exhaust or water-wash booth is a must.

AIR BRUSHES

At this point I disagree with Melvyn and suggest air brushes. A range of these are seized upon by Airfix aficionados for splattering NATO colours across their recently completed Centurian. Most modelling airbrushes will be too small, but in view of the hazards of spraying, I think it's far better to come up from too small than down from too big.

There are one or two brushes that actually will handle a pretty respectable amount of paint. At the cheap end, a couple of simple two nozzle and jar devices with a single pushbutton air control can be fairly effective, but will require thinning of the material to the manufacturer's maximum and an air supply of about ½ cfm at between 30 and 60 psi. The higher the available pressure, the less thinning will be required, but the increased spray bounce might be a problem on an uneven surface.

At the top end is the Paasche VLS, in sizes 1, 3 and 5. These sizes relate to optional needle and nozzle sizes, and the 5 is the more appropriate one for finishes. This type of brush has a single button which pushes down to turn the air on, and pulls back to move the needle back from the nozzle and allow the paint through in variable quantities.

To handle thicker paints more easily, the needle can be set further back in the carriage so that it can be pulled further clear of the nozzle. I have chucked buckets of paint on guitars with one of these, but they are expensive.

Most modelling air-brushes simply will not handle the quantities necessary for a guitar, and problems can arise finishing off a run of coating as part of it dries before you're through doing it all, which can leave an uneven surface dust.

But you still need a thoroughly ventilated and dust-free space, even if you can get away with slightly less than for a gun.

The toxic hazard still exists, but at a lower level.

PUFF THE MAGIC

You still need a decent air supply, too. I did a Microflame HS 410 diaphragm compressor briefly, which could push over ½ cfm at around 30 psi and 1 cfm at 20 psi. It wasn't too bad for small jobs with light finishes, but wouldn't run for long without taking a breather to cool down. It had to be operated from a section of heat-hose, and moisture traps on the airline, and while it struggled occasionally to produce enough puff, it was extremely quiet. Really, this is a modeller's compressor or a handy touch-up standby in a repair shop.

A gander in Exchange and Mart will show you what is available if you want to acquire a system. If you hire, then double check that the tank and piping is drained of moisture before you start. Many finishes will take up any tiny amount of airborne moisture and there is nothing quite so sickening as the whitish clouding whose sudden appearance on a guitar surface means you've got to do the bloody lot again.

A slightly cheaper and often more convenient way to get an air system is to build your own. Tanks and motors/compressors can be bought separately, fittings are usually BSP ¼in, adaptors are readily available, and the different components can be stashed in convenient corners and piped up together. The Danfoss switch is an important element as it will switch off the compressor when the tank reaches a preset pressure, and will then bleed off the air in the line between the compressor and the tank non return valve. The compressor can then start up again when required without having to fight a pressure that's there already. You'll need a regulator to deliver the required pressure at the spray nozzle, and moisture traps on long lengths of air-line, but much of the piping can be cannibalised. I used scrap air-pipe from a skip with the aid of a hacksaw and a tap and die set, and my tank moisture drain is an old gas-tap.

But the last point is the first consideration. How are you going to get rid of the fumes and mist without poisoning or blowing up yourself or your neighbours? If you can't do this, then you should forget DIY altogether. If you can do it, then be careful. If you blow your nose and your hanky goes the same colour as your guitar, then you've got problems.